I've always been curious about my own metabolism. When I was a teenaeger / in university I ate pretty badly. Chocolate bars every day after lunch, loads of carbs, not to mention alcohol, etc etc. I was rail thin. I once got a body fat assesment when I joined a gym (I did no exercise at all and this was a brief attempt to get buff) and the person doing the test was shocked and couldn't pinch anything to measure. I had no fat. This lasted till I was 25 where seemingly overnight I then had to watch what I eat or I started to gain fat. So what explains this seeming inability to gain weight no matter what I ate, and in my mid twenties having a more normal response to junk food?
How much "passive activity" were we doing back in the day?
So as a teenager, I was carrying 5-10kg of books and walking back and forth between classes every 40 mins.
As an undergrad I was travelling across campus multiple times a day, spent hours on my feet in labs, did multiple heavy grocery shuttles and also spent a lot of time partying.
In my first job, I was still getting up 5-6 times a day for meetings and had a decent walk/cycle built into the commute. but in my first remote job, I could be sat in the same spot for 8-10 hours without moving. And because I wasn't drinking water I wouldn't need to go to the bathroom... /facepalm I'd also be so engrossed that sometimes I'd forget to turn on the lights...
So even though I do more than an hour of intense exercise a day, my activity outside of those exercise hours has cratered from when I was a teenager and was constantly running around.
So as a teenager, I was carrying 5-10kg of books and walking back and forth between classes every 40 mins.
As an undergrad I was travelling across campus multiple times a day, spent hours on my feet in labs, did multiple heavy grocery shuttles and also spent a lot of time partying.
In my first job, I could be sat in the same spot for 8-10 hours without moving.
A year in to my first job I had added 15kg (~30lbs ~2stone) - while consuming way less food and alcohol than my university days.
I understand that as a healthy body sustains lifestyle damage, the effects begin to stack up, and then the effects become more noticeable, but it's not age based because it's reversible.
So look to your unhealthy lifestyle's accumulated effects in your body, atherosclerosis, obesity, pre-diabetes, hypertension, specific nutritional deficiencies, physiological mental health... And make a robust effort to improve your lifestyle, and you'll start to feel like you did, 10, 20 years ago.
Speaking from personal experience, I'm 50ish and after getting a health scare which triggered me into aggressive corrective action a few years back, I've overcorrected. My allergies have ameliorated back to old levels, I can drink beer again, and I can recover from a night out like I used to be able to in my 20's, I'm able to maintain a serious athletic schedule. Obviously most of the time I now eat really well, but my body's youthful tolerance to harm has been recovered.
Would love to hear what sort of things you did as part of your intervention?
Def noticing amongst my friends a few new allergies/intolerences manifesting as we get older
For some context am reasonably healthy and actually had to increase my sodium intake because I had over corrected on reducing salt consumption and was getting hyponatremic after training
In addition to activity levels, you probably just weren't eating that much food. It was similar for me when I was a teenager: some days I would binge on a ton of junk food, but other days I would forget to eat breakfast, and the latter happened often enough that I stayed skinny.
activity levels almost certainly. uni it's not impossible you were walking over 12k steps a day. that's 3-400 calories over the average american's daily steps of 4000.
That's also completely canceled out by enjoying a single 32oz soda. Walking a lot and having a bad diet rarely even each other out. And it's so easy to cancel it out I don't think most people realize. A brisk 2km walk burns less calories than are consumed when eating two regular Oreos.
As a student, I used a bus to get to school. As an adult, I walk by foot, more than an hour a day. Also, I didn't exercise in my youth, and I do now. Yet, it is now that I am fat.
I wonder about the same thing. I was a fat kid, but my best friend was so skinny. We would walk down town and he would stop several times to stuff chocolate bars in his mouth, and then buy two McDonald's meals. I would do none of this and our physical exercise was the same.
Then we went away to University and in his mid-20s the poor guy suddenly, almost overnight, put on a ton of weight.
Muscle burns more energy than fat. As people age, their muscle mass declines without sufficient exercise, so we'd naturally expect the average person's metabolism to decline via this even if "metabolism per kg muscle" didn't change.
In the paper they say that the daily energy expenditure matches well a function of the fat-free mass (a power-law function, at high masses the energy per mass ratio is lower than at low masses).
Therefore all their data is based only on fat-free mass, i.e. total body mass minus fat mass.
So all their conclusions are not influenced by the amount of fat vs. muscle.
But on the other hand, adding either muscle or fat burns more energy period, and we watch the average person's weight gain somewhere between 10 and 20 pounds over the first half of adulthood.
So we could easily expect the average person's metabolism to increase as well, simply to support the extra body mass regardless of composition.
Balancing out the two effects can only really be determined through careful statistics, and is going to be extremely variable per-person.
muscle burns very little calories, and even pro bodybuilders who have lots of muscle quickly put on fat off-season when not dieting. I don't think this explains it.
Muscle tissue burns 7-10 calories per pound per day. This means someone who gains 100 pounds of muscle (e.g. from 150 lbs untrained to a 250 lbs bodybuilder) would increase their metabolism by 700-1000 calories, almost a 50% increase in the average daily male calorie requirements of around 2000 calories.
It is essentially impossible to put on muscle at their size without also gaining fat, because they need to be in a large caloric surplus. During the off-season, pro bodybuilders are still training, they just increase their calorie intake significantly. Muscle does burn quite a few calories passively, it's just not nearly enough on a 260lb man to cover 6k-10k calorie intake.
There are multiple factors in maintaining bodyweight: diet, activity level, muscle mass, metabolism, etc. We shouldn't expect a single factor to explain everything, but holding eveything else constant, more muscle and the physical activity necessary to maintain it will burn more calories. It's an important part of maintaining health as we age.
they put on fat because the body fat level they compete at is unsustainable for long periods of time. additionally gaining fat is unavoidable when trying to gain muscle past a certain point.
Over my life I’ve been close to a small handful of perpetually skinny people who thought they had high metabolisms. In every case, when I watched them closely, I realized they barely ate anything.
My ex-gf was one of these people and would routinely tell people about how she could eat anything and not gain weight. But when I would go on a severely calorie-restricted diet I was still eating more than she did on a normal day. I don’t think she was lying about being able to eat anything, I think she just didn’t realize how little she actually ate.
Show me their Cronometer.com food/calorie diary and we'll see if the proposition even holds. Until then I'm not even willing to grant it's a thing.
In every case I guarantee they eat a normal amount of calories but feel like they eat a lot because they eat slightly more calories than normal in a single meal.
Like me eating two entrees at dinner at 16 and wowing everyone even though I skipped breakfast before school to play Runescape and had a tiny school lunch.
I'm not saying metabolism doesn't vary among individuals, I'm saying for a given individual, their overall metabolism could decrease as they age due to having less muscle mass even if their rate per kg muscle didn't change.
This is exactly the kind of clear headed reasoning from prior knowledge I love coming to Hacker News to see. You're right. Thank you for the extra bit of gym motivation.
No mention of how a persons lifestyle changes over that period though.
Surely there is a correlation to the causation?
The head-bone is connected to the neck-bone etc...
You cannot study figures in isolation and expect them to yield some meaningful results while ignoring the influence of other figures upon those results.
- Kids move around a lot, and they're still growing/developing
- Teenagers move more constructively i.e. sports, and they're still growing/developing
- Adults move a bit less, and have almost stopped growing/developing
- Older adults try do keep moving, but with other life responsibilities it gets hard to put the same time in
- Older adults become less and less bothered about moving
- Even older adults have acquired illness and injuries and can't move as much
Seems quite simple and obvious no? - Maybe...
Those that don't fit the mould have some other reason that makes then more of an outlier to the norm.
If life today didn't offer as much assistance as the past, we would all be a lot more healthy - not to mention more active, you know walking and manual work etc...
Not to forget that the abundance of food (good and bad) will have a bearing on the results. Maybe the older people that can't afford as much food are the outliers - and better benchmark.
Unless you are suffering from malnutrition, or you are overeating the wrong sort of food (good and bad) then your metabolism, unless affected by biological factors should be pretty stable.
Isn't this what being in homeostasis means?
Doesn't the body adapt to effects of S.A.I.D. - Specific Adaptations to Imposed Demands.
If inactivity was the explanation, it logically follows it would be possible to undo obesity by simply having people move more, but the evidence suggests exercise does not help compared to diet.
With no further context that graph is simply showing that exercise increases/maintains lean mass which will slow down absolute weight loss during a calorie deficit.
There's no exercise-only group on your graphic. So even though it's some random data without any context, it still can't say what you conclude it said.
The only criticism I see is some nitpicking saying that the claim “was based on statistical means, ignoring the known intense drops in the energy expenditure that some individuals show during their life. For example, a clear decrease in metabolic rate is observed in humans that consume calorie-restricted diets (Fothergill et al. 2016), an adaptation named ‘metabolic slowing’ (Johannsen et al. 2012). Therefore, the statement is innacurate and possibly wrong.”
These critics don’t seem to disagree with the core claim about average metabolism across the lifespan.
* Extreme events reveal an alimentary limit on sustained maximal human energy expenditure.
"We compiled measurements of total energy expenditure (TEE) and basal metabolic rate (BMR) from human endurance events and added new data from adults running ~250 km/week for 20 weeks in a transcontinental race. For events lasting 0.5 to 250+ days, SusMS decreases curvilinearly with event duration, plateauing below 3× BMR. This relationship differs from that of shorter events (e.g., marathons). Incorporating data from overfeeding studies, we find evidence for an alimentary energy supply limit in humans of ~2.5× BMR; greater expenditure requires drawing down the body’s energy stores. Transcontinental race data suggest that humans can partially reduce TEE during long events to extend endurance."
TRT is great for people who have true hypogonadism that can’t be fixed by other means. I had a friend growing up whose testosterone was under 100ng/dL no matter what he tried with his doctor. Finally got TRT and felt normal again.
However, after the honeymoon period the experience made him realize that not everything is explained and fixed by testosterone. He still had some mental health issues, he still had to work for gains at the gym, wasn’t suddenly full of boundless motivation. All this despite being put toward the upper end of the range for a long time.
This seems to be playing out with a lot of young people going to TRT clinics: The TRT clinics are prescription writing factories that will find an excuse to give almost anyone TRT. They make claims that the normal ranges are wrong and the only correct result is to be at the top of, or above, the reference range. They start people on insane beginning doses like 250mg/week because it gives them a rush to feel like it’s “working”, especially before their natural production shuts down.
The clinics also try to lock people into getting their prescriptions from the clinic in a subscription model. They basically get people hooked, literally dependent on testosterone because their endogenous production has shut down, and then require them to order the testosterone through their pharmacy to continue receiving the prescriptions. If they go to a family doctor, the family doctor will probably decline to continue writing such high dose prescriptions because high doses generate significant side effects, so the person returns to the TRT clinic.
It’s really bad out there. I think we’re headed for tighter regulation of these clinics soon, or at least I hope so. Every time I listen to the radio I get several ads for different clinics every hour promising men they will lose weight, be better in bed, have more energy, conquer the world.
I had low testosterone due to a brain injury, and going on TRT was absolutely life changing. I do wonder if it could be largely beneficial for older men in the same way hormone replacement therapy for post menopausal women is.
That said, permanently messing with your hormones as a younger person for no good reason is insane and I would try to talk anyone I knew out of it.
Fun fact: I had an endocrinologist at the University of Minnesota medical clinic tell me that going on TRT wouldn’t affect my fertility. Cue IVF 8 years later…
Convincing men at basically peak testosterone production to permanently impair their natural ability to produce it. It's awful. Not to mention the side effects of taking exogenous hormones e.g. damage to your liver...
Never mess with the endocrine system! the real killer for mens T levels, ie the perception of low T, is sitting around all day. I'm convinced that most people, men and women, feel terrible because they simply don't do nearly enough physical activity day to day. 20 hours of screens a day is not normal.
Super useful outcome, especially given I find that people think that after reaching even young ages 24, 25 even begin thinking that metabolism has some extreme drop off right after reaching young adulthood
It’s an inevitable outcome of a culture so focused on age. I watch twitch streamers in their 20’s talking about how they’re old already. Narcissism isn’t just a social phenomenon spread online, I think it actively contributes to many public health concerns we’re seeing today.
I agree with your observation, but at the same time, I do think that what a lot of these people might be expressing is their observation of the disconnect between their socially implanted expectations (you're an adult when your 18/21! you are now -mature-), and their experience reality. Which is that for many (most?) people who go through the typical North American education pipeline through university/college (and I'm only making this limitation because that's my experience, and the experience of most of my friends), that looking back, they were definitely not "mature" at 18/21. They probably weren't even mature when they graduated undergrad or started their first full time job out of school.
Everyone has a different point, but they typically recognize somewhere in their 20s that 'oh wow, we keep changing and maturing'. And the first, most basic way to express this observation is with a pretty crude 'oh wow I'm old'. I think eventually, most people can move beyond that first reflexive observation.
So the results show that on average, metabolism is stable from 20 years onward. That means that there actually is a drop from 18 to 25 (it's there for men at least when you look at Fig 2). Now think about where most people will be anchoring their perception of "adult" from (it's going to be some value in that range). That means that there will absolutely be plenty of people who experience a real decline in metabolism in the years following their "personal adult threshold".
Now, that's a pretty small drop, so definitely the other life transition (probably starting an office job, living alone) will probably play an even larger part to any weight related changes. But even given a hypothetical case where someone kept the exact same activity level, the amount of metabolism decline over that period is probably small enough to delay the onset of any noticeable body composition change (like order of 10 pounds) for a few years, adding to the mid to late 20s experience.
Such rumors are created and spread by people who want an excuse rather than a solution. This wont help them since they want to cling to their excuses, but it can help others ignore those rumors.
I found the misconception useful because it prompted me to invest time in improving my diet in my 20s, before it was too late. Even if my metabolism has stayed the same since then, the no-vegetables-or-fruits approach would have caught up with me at the same time "low metabolism" would.
Anecdata: I ate 3500-4000 calories a day of mostly junk in high school and college. I lifted weights some. I (barely) “had a six-pack”. No sports, only incidental cardio.
Around age 21 or so, I decided to try to drop a couple pounds and make it a really cut six-pack. I ate a strict 1400 calorie diet (packaged food to make it easy, no cheating at all) for about three months. I started running a couple times a week. I’d reckoned this would only take a month or so. Found the calorie deficit pretty easy, actually. Three months in, the scale showed one pound of loss.
Discouraged, I returned to my old eating habits.
I immediately gained about 15lb. Had to drop soda completely to stabilize it (i didn’t drink much alcohol then). Slowly got worse through my 20s. By 30, not turning into a blimp required a careful diet. No more 4k+ calories of pizza, soda, and potato chips without (visible) consequence.
My metabolism 100% for-sure changed in my 20s, a ton, not gradually. But I may have killed it, and perhaps I would have been able to keep doing what I was doing another couple decades otherwise (I would bet zero dollars on it, but hey, I guess the science disagrees, I just find it literally incredible)
Those are the figures people always estimate. Always the same story: 4000 calories when they were skinny, and now they can't lose weight on 1500 calories when their maintenance intake is 2600.
Then you make them log their food for a week and they are eating 3000 calories when they swore they ate no more than 2000. In my 20s I worked at a personal trainer in a gym that made people log their food and 100% of people said the same thing you just did.
If you couldn't lose weight on 1400 calories then where exactly was the energy coming from? Cue the "starvation mode" meme where people claim their body becomes so efficient that it only needs 1400 calories to maintain their 270lb body.
this seems to agree with a lot of people's personal accounts. A switch is flipped in which the body for whatever reasons starts hording energy. maybe it is stress from family life or work related... who knows...The weight comes on so fast... it's nuts how much weight some people gain starting at 25 or so. Guys who were 130-180 lbs lean in college now 240+ lbs all a sudden at 30+.
According to the paper this is "Fat-free mass-adjusted expenditure", and testosterone DOES start to slowly decline after around age 25. The trouble people have with starting to gain weight easier as they enter their 30s and 40s is caused by this since they'll lose muscle mass as such hormones decline, which causes fat gain assuming similar food intake and activity levels, this effect is not included by adjusting for fat-free mass.
I also think 30-40 is more likely caused by life just being more complicated! Juggling kids is basically a full time job, and many families are two income families. Hard to hit the gym when your child, who cannot be left alone, increases your effective work hours to 80-90/week minimum no vacation no breaks.
I think thats basically true for most people, hence the belief that metabolism slows with age.
Proving that its not metabolism would imply that our weight gain in later life is a combination of other factors. I would bet good money on the increase in sedentary leisure activities, the reliance on motorised vehicles and a lack of energy to be active.
I would bet on those long before anything as nebulous as diet or intake volume.
Have kids and compare yourself against them. It truly sobering to see how much relentless energy hey have, in body and mind (and when they hit the wall with burning out all energy, they hit hard). All the movement is just burning through all energy. I feel myself very active, but next to my 3 year old son I feel glacial and lazy.
We can reverse that, like we can revere many ways we slowly decline, just need a right mindset. Spend a really active vacation or start a new sport and lack of energy of yesterday will be gone, to certain extent. One can always do some dramatic change in lifestyle to see a dramatic change in body, weight, strength, stamina etc.
I see as people get older their mental model of how they behave and think often mimics somebody much older than their actual age, acting as if they are completely powerless to greater evil forces of muscle atrophy and weight gain. It simply ain't true but going against it is certainly harder than just complain.
I can think of two major, extra lifestyle factors that increase calories in adulthood that we overlook in favor of more appealing explanations like "metabolism tho":
1. We eat out more as adults. Our skinny kid/teen selves didn't even have the money/vehicle/norm to eat out much less do it daily like we can as adults. This also includes eating out during our lunch break. Every time we eat out that's an easy 1000+ calories.
2. When you live with a partner, every time they ask "wanna eat something?" and you say "yes", that's a moment you wouldn't have eaten had you been a bachelor. We'll even say yes when we aren't hungry.
It's funny how much we want to believe in factors out of our control.
yep, so many people go from 10k steps a day in college to 5k in an entry level position to 1k in a desk role. for a 200lb 6 ft tall male, thats 3000 kcal burned a day to 2600, to 2300. 700kcal a day being a weight change total of around 1.5 lb a week when you consider days off.
Anecdotally, to me it seems like my metabolism hasn't changed. I was overweight when I was younger because I overate. Now I don't, and my weight is normal, on the low end for my height. But nothing about the quantities turning into pounds changed, from my p.o.v. (mid 40s now).
Actually the main thing that changed for me is I started compressing all my eating into 1-2 meals per day. That way I could track it. Before I couldn't tell you if "I haven't changed my diet" because it was a continuum of eating from morning till night. I have no idea what changed over time, couldn't even tell you for one week. Once I "bounded" it I was able to bring my weight down quickly.
Btw, sorry if this sounds snarky, it seemed like flagging this as anecdotal was the right way to start so I copied it.
That is likely down to the type of "food" that you are eating. Or you are eating more than is necessary.
A diet that contains a high nutritional content will prevent you from over-eating due to satiety signals (unless you have a hormone issue) rather than eating to the point of feeling "stuffed" - if someone is eating to the point of feeling "stuffed" then it would suggest that they are not eating food with a high nutritional content, or that they have some disorder that is interfering with their normal eating process.
If you look to the animal kingdom, the lion kills the zebra, feeds then walks away, the next in line feeds, then walks away, etc, etc... no animal eats until they are "stuffed" - if they did then they would become another animals prey because they are too "stuffed" to move!
No wonder some countries consider it rude to clear your plate of food.
(too bad the Brits do this the other way around!) lol
A diet that contains a high nutritional content will prevent you from over-eating due to satiety signals (unless you have a hormone issue) rather than eating to the point of feeling "stuffed" - if someone is eating to the point of feeling "stuffed" then it would suggest that they are not eating food with a high nutritional content, or that they have some disorder that is interfering with their normal eating process.
if this were true it would be possible to create a diet full of foods with such satiety signals and the obesity crisis could be fixed. way easier said than done. 7-grain bread is very nutritious yet a loaf is easily 1000+ calories. Easy to overeat on it given it's just mostly air.
Without a meticulous food diary for comparison, you can't substantiate that you are eating the same or fewer calories. And if you can't do that, then there's no mystery here.
If you are eating 3000 calories of healthy food and you used to eat 2400 calories of junk food, why would you weigh less now?
Are you eating with the same consistency as when you were young? Are you walking the same amount as you used to? Are you partying with the same frequency? Etc.
There's a theory that you're gut is optimizing over your life. So you were young, and you could eat garbage by the truck load and not see a pound. You're now eating better and exercising portion control, but your body has learned how to extract everything it can from food.
USA based. I was born in 1968 rebelled against my organic gardening and bread baking mom every chance I got. I weighed around 135 pounds in college and currently weigh 143. I have been as heavy as 147ish that I noticed.
There is probably some larger environmental factor that causing the majority of people to gain weight. Whatever it is started in the 1970s in the US, and has since spread to most of the rest of the world. Possibly plasticizers, or some other chemical. Even children are much heavier now.
I ain't buying it. There is a replication crisis in the sciences, and it would not surprise me if this is wrong too, or at least that the results do not mean what they are purported to mean. I have read many personal accounts here and elsewhere of men who were able to eat a lot in their late teens, 20s, and early 30s, and then suddenly by their 30s gain a lot of weight despite not changing their lifestyle or diet much.
Inactivity alone does not explain it. Consider for example Bill Gate...according to his resume, in which he lists his precise height and weight, in his 20s he weighed just 125 pounds. It's evident he has put on a lot of weight, all in his mid-section, well before he turned 60. His job literally entailed sitting at a computer all day coding. If anything, given his philanthropy efforts and retirement, he is more active now than he was in his 20s when working full-time at Microsoft. Is he eating more? I doubt it.
For so many people, celebrities for example, a switch is flipped in which there is sudden weight gain after the age of 30 or so, like John Travolta, Stevie Wonder and others. Because celebrities are photographed, you can see the weight progression and the abrupt jump in weight. Even with money for personal chefs and trainers, not gaining weight is hard.
I can personally attest that if I ate the same quantity of food now as I did at 20 I would gain weight, and no I'm not 60. And I am just as active , maybe more so. So yeah not buying this study.
What's the age at which anti-aging interventions are most impactful?
I assume they don't help much when you're young, because you're already healthy as a youth.
Presumably waiting until you're on your deathbed to start high-intensity intervals is not the best idea either.
Supposing a person had a limited budget of "anti-aging firepower" in the form of pills, exercise, etc. -- what age would be most impactful to apply it?
That is way too complex a question to answer here. If you really want to dig into it including exercise, nutrition, sleep, and medications then the new book "Outlive: The Science & Art of Longevity" by Dr. Peter Attia is a pretty good summary of what we currently know.
Mid 20s with when your lifestyle shift just starts to catch up to you.
You go from a more active young person that eats just enough to get back to hanging with friends to binge drinking in an instant. Then you go from that to a much lazier, snackier lifestyle of 9-5.
Yeah, people on the whole do get fatter in their 30s, but that’s very easily linkable to lifestyle.
This is interesting for me to see. For the longest while I was wondering why through my 40s and later I didn't seem to be hit with middle-aged weight gain, all while living my sedentary life in the computer chair. I wouldn't classify myself as average though, I've always had low heart rate/low blood pressure and low blood sugar. Swimming in salt-water is fun because I can float without much effort.
I did notice a decline in metabolism/muscle mass in the past several years, so I took to walking rather than driving in the city/neighbourhood and eating more and regularly which seems to have brought my levels back up somewhat. Now I look like someone who only goes to the gym on leg days.
This was completely expected, at the macro level this is easily observed by measuring the outputs of metabolism and bodily function, mainly heat and physical activity. All humans have a baseline bodily temperature, meaning that the inner metabolism also is the same across all humans.
Sweating at different rates, surface blood vessel dilation including in your lungs, all change the flux. Having longer hair or wearing warmer clothing can too and can be balanced by those other things. Activity also gets balanced by those things. Eating cold food and drink vs warm etc.
That we maintain a baseline temperature doesn't tell you that metabolism alone is all that regulates it, there are other factors.
I've always been curious about my own metabolism. When I was a teenaeger / in university I ate pretty badly. Chocolate bars every day after lunch, loads of carbs, not to mention alcohol, etc etc. I was rail thin. I once got a body fat assesment when I joined a gym (I did no exercise at all and this was a brief attempt to get buff) and the person doing the test was shocked and couldn't pinch anything to measure. I had no fat. This lasted till I was 25 where seemingly overnight I then had to watch what I eat or I started to gain fat. So what explains this seeming inability to gain weight no matter what I ate, and in my mid twenties having a more normal response to junk food?
How much "passive activity" were we doing back in the day?
So as a teenager, I was carrying 5-10kg of books and walking back and forth between classes every 40 mins.
As an undergrad I was travelling across campus multiple times a day, spent hours on my feet in labs, did multiple heavy grocery shuttles and also spent a lot of time partying.
In my first job, I was still getting up 5-6 times a day for meetings and had a decent walk/cycle built into the commute. but in my first remote job, I could be sat in the same spot for 8-10 hours without moving. And because I wasn't drinking water I wouldn't need to go to the bathroom... /facepalm I'd also be so engrossed that sometimes I'd forget to turn on the lights...
So even though I do more than an hour of intense exercise a day, my activity outside of those exercise hours has cratered from when I was a teenager and was constantly running around.
So as a teenager, I was carrying 5-10kg of books and walking back and forth between classes every 40 mins.
As an undergrad I was travelling across campus multiple times a day, spent hours on my feet in labs, did multiple heavy grocery shuttles and also spent a lot of time partying.
In my first job, I could be sat in the same spot for 8-10 hours without moving.
A year in to my first job I had added 15kg (~30lbs ~2stone) - while consuming way less food and alcohol than my university days.
I actually lost weight upon entering college because my campus was so large that my physical activity increased from when I was in high school.
I understand that as a healthy body sustains lifestyle damage, the effects begin to stack up, and then the effects become more noticeable, but it's not age based because it's reversible.
So look to your unhealthy lifestyle's accumulated effects in your body, atherosclerosis, obesity, pre-diabetes, hypertension, specific nutritional deficiencies, physiological mental health... And make a robust effort to improve your lifestyle, and you'll start to feel like you did, 10, 20 years ago.
Speaking from personal experience, I'm 50ish and after getting a health scare which triggered me into aggressive corrective action a few years back, I've overcorrected. My allergies have ameliorated back to old levels, I can drink beer again, and I can recover from a night out like I used to be able to in my 20's, I'm able to maintain a serious athletic schedule. Obviously most of the time I now eat really well, but my body's youthful tolerance to harm has been recovered.
Would love to hear what sort of things you did as part of your intervention?
Def noticing amongst my friends a few new allergies/intolerences manifesting as we get older
For some context am reasonably healthy and actually had to increase my sodium intake because I had over corrected on reducing salt consumption and was getting hyponatremic after training
1 reply →
In addition to activity levels, you probably just weren't eating that much food. It was similar for me when I was a teenager: some days I would binge on a ton of junk food, but other days I would forget to eat breakfast, and the latter happened often enough that I stayed skinny.
No I legit ate way much much more in my 20s. I'm not misremembering. I ate more
20 replies →
activity levels almost certainly. uni it's not impossible you were walking over 12k steps a day. that's 3-400 calories over the average american's daily steps of 4000.
That's also completely canceled out by enjoying a single 32oz soda. Walking a lot and having a bad diet rarely even each other out. And it's so easy to cancel it out I don't think most people realize. A brisk 2km walk burns less calories than are consumed when eating two regular Oreos.
50 replies →
As a student, I used a bus to get to school. As an adult, I walk by foot, more than an hour a day. Also, I didn't exercise in my youth, and I do now. Yet, it is now that I am fat.
I wonder about the same thing. I was a fat kid, but my best friend was so skinny. We would walk down town and he would stop several times to stuff chocolate bars in his mouth, and then buy two McDonald's meals. I would do none of this and our physical exercise was the same.
Then we went away to University and in his mid-20s the poor guy suddenly, almost overnight, put on a ton of weight.
25 is about the age you’ve worked a year two after an undergrad. More money means more desk work and more access (speaking funds) to eat out
I had a similar trajectory. The transition from one to the other was a long course of antibiotics.
Muscle burns more energy than fat. As people age, their muscle mass declines without sufficient exercise, so we'd naturally expect the average person's metabolism to decline via this even if "metabolism per kg muscle" didn't change.
In the paper they say that the daily energy expenditure matches well a function of the fat-free mass (a power-law function, at high masses the energy per mass ratio is lower than at low masses).
Therefore all their data is based only on fat-free mass, i.e. total body mass minus fat mass.
So all their conclusions are not influenced by the amount of fat vs. muscle.
But on the other hand, adding either muscle or fat burns more energy period, and we watch the average person's weight gain somewhere between 10 and 20 pounds over the first half of adulthood.
So we could easily expect the average person's metabolism to increase as well, simply to support the extra body mass regardless of composition.
Balancing out the two effects can only really be determined through careful statistics, and is going to be extremely variable per-person.
There's good evidence that metabolic rate does vary, but not significantly.
https://examine.com/articles/does-metabolism-vary-between-tw...
10 replies →
"Even when you’re sleeping at night, the brain consumes roughly as much energy as it does during the day."
https://www.brainfacts.org/brain-anatomy-and-function/anatom...
Does this change over time also?
I wouldn’t trust a site called BrainFacts to be unbiased given the source.
muscle burns very little calories, and even pro bodybuilders who have lots of muscle quickly put on fat off-season when not dieting. I don't think this explains it.
Muscle tissue burns 7-10 calories per pound per day. This means someone who gains 100 pounds of muscle (e.g. from 150 lbs untrained to a 250 lbs bodybuilder) would increase their metabolism by 700-1000 calories, almost a 50% increase in the average daily male calorie requirements of around 2000 calories.
12 replies →
It is essentially impossible to put on muscle at their size without also gaining fat, because they need to be in a large caloric surplus. During the off-season, pro bodybuilders are still training, they just increase their calorie intake significantly. Muscle does burn quite a few calories passively, it's just not nearly enough on a 260lb man to cover 6k-10k calorie intake.
There are multiple factors in maintaining bodyweight: diet, activity level, muscle mass, metabolism, etc. We shouldn't expect a single factor to explain everything, but holding eveything else constant, more muscle and the physical activity necessary to maintain it will burn more calories. It's an important part of maintaining health as we age.
they put on fat because the body fat level they compete at is unsustainable for long periods of time. additionally gaining fat is unavoidable when trying to gain muscle past a certain point.
1 reply →
A lot of skinny people have high metabolism, how do you explain that?
Over my life I’ve been close to a small handful of perpetually skinny people who thought they had high metabolisms. In every case, when I watched them closely, I realized they barely ate anything.
My ex-gf was one of these people and would routinely tell people about how she could eat anything and not gain weight. But when I would go on a severely calorie-restricted diet I was still eating more than she did on a normal day. I don’t think she was lying about being able to eat anything, I think she just didn’t realize how little she actually ate.
16 replies →
Show me their Cronometer.com food/calorie diary and we'll see if the proposition even holds. Until then I'm not even willing to grant it's a thing.
In every case I guarantee they eat a normal amount of calories but feel like they eat a lot because they eat slightly more calories than normal in a single meal.
Like me eating two entrees at dinner at 16 and wowing everyone even though I skipped breakfast before school to play Runescape and had a tiny school lunch.
2 replies →
Those skinny people most likely have a very inefficient metabolism or at the very least a very adaptable one.
Their mitochondria use UCP1 [1][2] to generate more heat when producing ATP, thus wasting energy that would otherwise be converted to fat.
[1] https://en.m.wikipedia.org/wiki/Uncoupling_protein
[2] https://en.m.wikipedia.org/wiki/Thermogenin
1 reply →
I'm not saying metabolism doesn't vary among individuals, I'm saying for a given individual, their overall metabolism could decrease as they age due to having less muscle mass even if their rate per kg muscle didn't change.
2 replies →
Casual factor. Higher base metabolic rate means less energy available to build body mass.
Fidgeting.
9 replies →
How do you know those skinny people actually have high metabolism? Have they quantified it with a resting metabolic rate test?
I have two friends like that, both were diagnosed with thyroid issues
So to answer you question, hormones
Likely genetic, such as beta adrenergic receptors.
This is exactly the kind of clear headed reasoning from prior knowledge I love coming to Hacker News to see. You're right. Thank you for the extra bit of gym motivation.
No mention of how a persons lifestyle changes over that period though.
Surely there is a correlation to the causation?
The head-bone is connected to the neck-bone etc...
You cannot study figures in isolation and expect them to yield some meaningful results while ignoring the influence of other figures upon those results.
- Kids move around a lot, and they're still growing/developing
- Teenagers move more constructively i.e. sports, and they're still growing/developing
- Adults move a bit less, and have almost stopped growing/developing
- Older adults try do keep moving, but with other life responsibilities it gets hard to put the same time in
- Older adults become less and less bothered about moving
- Even older adults have acquired illness and injuries and can't move as much
Seems quite simple and obvious no? - Maybe...
Those that don't fit the mould have some other reason that makes then more of an outlier to the norm.
If life today didn't offer as much assistance as the past, we would all be a lot more healthy - not to mention more active, you know walking and manual work etc...
Not to forget that the abundance of food (good and bad) will have a bearing on the results. Maybe the older people that can't afford as much food are the outliers - and better benchmark.
Unless you are suffering from malnutrition, or you are overeating the wrong sort of food (good and bad) then your metabolism, unless affected by biological factors should be pretty stable.
Isn't this what being in homeostasis means?
Doesn't the body adapt to effects of S.A.I.D. - Specific Adaptations to Imposed Demands.
If inactivity was the explanation, it logically follows it would be possible to undo obesity by simply having people move more, but the evidence suggests exercise does not help compared to diet.
https://cdn.vox-cdn.com/thumbor/U1RxtW9oglcck-2g2X_SrKzIA44=...
With no further context that graph is simply showing that exercise increases/maintains lean mass which will slow down absolute weight loss during a calorie deficit.
There's no exercise-only group on your graphic. So even though it's some random data without any context, it still can't say what you conclude it said.
Did anyone happen to read any of the responses to the article at https://www.science.org/
It seems that others don't fully support their findings either.
https://www.science.org/doi/10.1126/science.abe5017#eletters...
The only criticism I see is some nitpicking saying that the claim “was based on statistical means, ignoring the known intense drops in the energy expenditure that some individuals show during their life. For example, a clear decrease in metabolic rate is observed in humans that consume calorie-restricted diets (Fothergill et al. 2016), an adaptation named ‘metabolic slowing’ (Johannsen et al. 2012). Therefore, the statement is innacurate and possibly wrong.”
These critics don’t seem to disagree with the core claim about average metabolism across the lifespan.
* Extreme events reveal an alimentary limit on sustained maximal human energy expenditure.
"We compiled measurements of total energy expenditure (TEE) and basal metabolic rate (BMR) from human endurance events and added new data from adults running ~250 km/week for 20 weeks in a transcontinental race. For events lasting 0.5 to 250+ days, SusMS decreases curvilinearly with event duration, plateauing below 3× BMR. This relationship differs from that of shorter events (e.g., marathons). Incorporating data from overfeeding studies, we find evidence for an alimentary energy supply limit in humans of ~2.5× BMR; greater expenditure requires drawing down the body’s energy stores. Transcontinental race data suggest that humans can partially reduce TEE during long events to extend endurance."
https://www.science.org/doi/full/10.1126/sciadv.aaw0341
Another sobering result for the fitness industry, that convinces 30 year old men to be on TRT.
TRT is great for people who have true hypogonadism that can’t be fixed by other means. I had a friend growing up whose testosterone was under 100ng/dL no matter what he tried with his doctor. Finally got TRT and felt normal again.
However, after the honeymoon period the experience made him realize that not everything is explained and fixed by testosterone. He still had some mental health issues, he still had to work for gains at the gym, wasn’t suddenly full of boundless motivation. All this despite being put toward the upper end of the range for a long time.
This seems to be playing out with a lot of young people going to TRT clinics: The TRT clinics are prescription writing factories that will find an excuse to give almost anyone TRT. They make claims that the normal ranges are wrong and the only correct result is to be at the top of, or above, the reference range. They start people on insane beginning doses like 250mg/week because it gives them a rush to feel like it’s “working”, especially before their natural production shuts down.
The clinics also try to lock people into getting their prescriptions from the clinic in a subscription model. They basically get people hooked, literally dependent on testosterone because their endogenous production has shut down, and then require them to order the testosterone through their pharmacy to continue receiving the prescriptions. If they go to a family doctor, the family doctor will probably decline to continue writing such high dose prescriptions because high doses generate significant side effects, so the person returns to the TRT clinic.
It’s really bad out there. I think we’re headed for tighter regulation of these clinics soon, or at least I hope so. Every time I listen to the radio I get several ads for different clinics every hour promising men they will lose weight, be better in bed, have more energy, conquer the world.
I had low testosterone due to a brain injury, and going on TRT was absolutely life changing. I do wonder if it could be largely beneficial for older men in the same way hormone replacement therapy for post menopausal women is.
That said, permanently messing with your hormones as a younger person for no good reason is insane and I would try to talk anyone I knew out of it.
Fun fact: I had an endocrinologist at the University of Minnesota medical clinic tell me that going on TRT wouldn’t affect my fertility. Cue IVF 8 years later…
4 replies →
Convincing men at basically peak testosterone production to permanently impair their natural ability to produce it. It's awful. Not to mention the side effects of taking exogenous hormones e.g. damage to your liver...
I see a study suggesting that, in hypogonadal men (important), TTh or TRT seems to improve their liver.
This seems to be contradicting your claim: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8451678/
3 replies →
Peak? We're talking about 30 year olds.
For some it's not really convincing. They look at it like doctor perscribed steroids.
2 replies →
Never mess with the endocrine system! the real killer for mens T levels, ie the perception of low T, is sitting around all day. I'm convinced that most people, men and women, feel terrible because they simply don't do nearly enough physical activity day to day. 20 hours of screens a day is not normal.
Super useful outcome, especially given I find that people think that after reaching even young ages 24, 25 even begin thinking that metabolism has some extreme drop off right after reaching young adulthood
It’s an inevitable outcome of a culture so focused on age. I watch twitch streamers in their 20’s talking about how they’re old already. Narcissism isn’t just a social phenomenon spread online, I think it actively contributes to many public health concerns we’re seeing today.
I agree with your observation, but at the same time, I do think that what a lot of these people might be expressing is their observation of the disconnect between their socially implanted expectations (you're an adult when your 18/21! you are now -mature-), and their experience reality. Which is that for many (most?) people who go through the typical North American education pipeline through university/college (and I'm only making this limitation because that's my experience, and the experience of most of my friends), that looking back, they were definitely not "mature" at 18/21. They probably weren't even mature when they graduated undergrad or started their first full time job out of school.
Everyone has a different point, but they typically recognize somewhere in their 20s that 'oh wow, we keep changing and maturing'. And the first, most basic way to express this observation is with a pretty crude 'oh wow I'm old'. I think eventually, most people can move beyond that first reflexive observation.
3 replies →
So the results show that on average, metabolism is stable from 20 years onward. That means that there actually is a drop from 18 to 25 (it's there for men at least when you look at Fig 2). Now think about where most people will be anchoring their perception of "adult" from (it's going to be some value in that range). That means that there will absolutely be plenty of people who experience a real decline in metabolism in the years following their "personal adult threshold".
Now, that's a pretty small drop, so definitely the other life transition (probably starting an office job, living alone) will probably play an even larger part to any weight related changes. But even given a hypothetical case where someone kept the exact same activity level, the amount of metabolism decline over that period is probably small enough to delay the onset of any noticeable body composition change (like order of 10 pounds) for a few years, adding to the mid to late 20s experience.
Such rumors are created and spread by people who want an excuse rather than a solution. This wont help them since they want to cling to their excuses, but it can help others ignore those rumors.
I found the misconception useful because it prompted me to invest time in improving my diet in my 20s, before it was too late. Even if my metabolism has stayed the same since then, the no-vegetables-or-fruits approach would have caught up with me at the same time "low metabolism" would.
Anecdata: I ate 3500-4000 calories a day of mostly junk in high school and college. I lifted weights some. I (barely) “had a six-pack”. No sports, only incidental cardio.
Around age 21 or so, I decided to try to drop a couple pounds and make it a really cut six-pack. I ate a strict 1400 calorie diet (packaged food to make it easy, no cheating at all) for about three months. I started running a couple times a week. I’d reckoned this would only take a month or so. Found the calorie deficit pretty easy, actually. Three months in, the scale showed one pound of loss.
Discouraged, I returned to my old eating habits.
I immediately gained about 15lb. Had to drop soda completely to stabilize it (i didn’t drink much alcohol then). Slowly got worse through my 20s. By 30, not turning into a blimp required a careful diet. No more 4k+ calories of pizza, soda, and potato chips without (visible) consequence.
My metabolism 100% for-sure changed in my 20s, a ton, not gradually. But I may have killed it, and perhaps I would have been able to keep doing what I was doing another couple decades otherwise (I would bet zero dollars on it, but hey, I guess the science disagrees, I just find it literally incredible)
I don't buy your anecdote.
Those are the figures people always estimate. Always the same story: 4000 calories when they were skinny, and now they can't lose weight on 1500 calories when their maintenance intake is 2600.
Then you make them log their food for a week and they are eating 3000 calories when they swore they ate no more than 2000. In my 20s I worked at a personal trainer in a gym that made people log their food and 100% of people said the same thing you just did.
If you couldn't lose weight on 1400 calories then where exactly was the energy coming from? Cue the "starvation mode" meme where people claim their body becomes so efficient that it only needs 1400 calories to maintain their 270lb body.
2 replies →
Teens are growing until early 20s that’s why they can and do eat so much. When you stop growing you enter into your adult metabolism.
I started gaining weight/fat in my mid 20s and had to adjust my eating habits from what was normal in the preceding 8-10 years
2 replies →
same here but at a later age
this seems to agree with a lot of people's personal accounts. A switch is flipped in which the body for whatever reasons starts hording energy. maybe it is stress from family life or work related... who knows...The weight comes on so fast... it's nuts how much weight some people gain starting at 25 or so. Guys who were 130-180 lbs lean in college now 240+ lbs all a sudden at 30+.
According to the paper this is "Fat-free mass-adjusted expenditure", and testosterone DOES start to slowly decline after around age 25. The trouble people have with starting to gain weight easier as they enter their 30s and 40s is caused by this since they'll lose muscle mass as such hormones decline, which causes fat gain assuming similar food intake and activity levels, this effect is not included by adjusting for fat-free mass.
I also think 30-40 is more likely caused by life just being more complicated! Juggling kids is basically a full time job, and many families are two income families. Hard to hit the gym when your child, who cannot be left alone, increases your effective work hours to 80-90/week minimum no vacation no breaks.
Anecdotally: I havent changed diet one bit, actually I eat way healthier than when I was younger.
And still weigh much more than when younger.
I think thats basically true for most people, hence the belief that metabolism slows with age.
Proving that its not metabolism would imply that our weight gain in later life is a combination of other factors. I would bet good money on the increase in sedentary leisure activities, the reliance on motorised vehicles and a lack of energy to be active.
I would bet on those long before anything as nebulous as diet or intake volume.
Have kids and compare yourself against them. It truly sobering to see how much relentless energy hey have, in body and mind (and when they hit the wall with burning out all energy, they hit hard). All the movement is just burning through all energy. I feel myself very active, but next to my 3 year old son I feel glacial and lazy.
We can reverse that, like we can revere many ways we slowly decline, just need a right mindset. Spend a really active vacation or start a new sport and lack of energy of yesterday will be gone, to certain extent. One can always do some dramatic change in lifestyle to see a dramatic change in body, weight, strength, stamina etc.
I see as people get older their mental model of how they behave and think often mimics somebody much older than their actual age, acting as if they are completely powerless to greater evil forces of muscle atrophy and weight gain. It simply ain't true but going against it is certainly harder than just complain.
1 reply →
I can think of two major, extra lifestyle factors that increase calories in adulthood that we overlook in favor of more appealing explanations like "metabolism tho":
1. We eat out more as adults. Our skinny kid/teen selves didn't even have the money/vehicle/norm to eat out much less do it daily like we can as adults. This also includes eating out during our lunch break. Every time we eat out that's an easy 1000+ calories.
2. When you live with a partner, every time they ask "wanna eat something?" and you say "yes", that's a moment you wouldn't have eaten had you been a bachelor. We'll even say yes when we aren't hungry.
It's funny how much we want to believe in factors out of our control.
1 reply →
yep, so many people go from 10k steps a day in college to 5k in an entry level position to 1k in a desk role. for a 200lb 6 ft tall male, thats 3000 kcal burned a day to 2600, to 2300. 700kcal a day being a weight change total of around 1.5 lb a week when you consider days off.
10 replies →
Anecdotally, to me it seems like my metabolism hasn't changed. I was overweight when I was younger because I overate. Now I don't, and my weight is normal, on the low end for my height. But nothing about the quantities turning into pounds changed, from my p.o.v. (mid 40s now).
Actually the main thing that changed for me is I started compressing all my eating into 1-2 meals per day. That way I could track it. Before I couldn't tell you if "I haven't changed my diet" because it was a continuum of eating from morning till night. I have no idea what changed over time, couldn't even tell you for one week. Once I "bounded" it I was able to bring my weight down quickly.
Btw, sorry if this sounds snarky, it seemed like flagging this as anecdotal was the right way to start so I copied it.
That is likely down to the type of "food" that you are eating. Or you are eating more than is necessary.
A diet that contains a high nutritional content will prevent you from over-eating due to satiety signals (unless you have a hormone issue) rather than eating to the point of feeling "stuffed" - if someone is eating to the point of feeling "stuffed" then it would suggest that they are not eating food with a high nutritional content, or that they have some disorder that is interfering with their normal eating process.
If you look to the animal kingdom, the lion kills the zebra, feeds then walks away, the next in line feeds, then walks away, etc, etc... no animal eats until they are "stuffed" - if they did then they would become another animals prey because they are too "stuffed" to move!
No wonder some countries consider it rude to clear your plate of food. (too bad the Brits do this the other way around!) lol
A diet that contains a high nutritional content will prevent you from over-eating due to satiety signals (unless you have a hormone issue) rather than eating to the point of feeling "stuffed" - if someone is eating to the point of feeling "stuffed" then it would suggest that they are not eating food with a high nutritional content, or that they have some disorder that is interfering with their normal eating process.
if this were true it would be possible to create a diet full of foods with such satiety signals and the obesity crisis could be fixed. way easier said than done. 7-grain bread is very nutritious yet a loaf is easily 1000+ calories. Easy to overeat on it given it's just mostly air.
3 replies →
Without a meticulous food diary for comparison, you can't substantiate that you are eating the same or fewer calories. And if you can't do that, then there's no mystery here.
If you are eating 3000 calories of healthy food and you used to eat 2400 calories of junk food, why would you weigh less now?
Are you eating with the same consistency as when you were young? Are you walking the same amount as you used to? Are you partying with the same frequency? Etc.
Eating too much for sure. When younger average person spend more time outside, traveling more etc.
There's a theory that you're gut is optimizing over your life. So you were young, and you could eat garbage by the truck load and not see a pound. You're now eating better and exercising portion control, but your body has learned how to extract everything it can from food.
USA based. I was born in 1968 rebelled against my organic gardening and bread baking mom every chance I got. I weighed around 135 pounds in college and currently weigh 143. I have been as heavy as 147ish that I noticed.
There is probably some larger environmental factor that causing the majority of people to gain weight. Whatever it is started in the 1970s in the US, and has since spread to most of the rest of the world. Possibly plasticizers, or some other chemical. Even children are much heavier now.
I ain't buying it. There is a replication crisis in the sciences, and it would not surprise me if this is wrong too, or at least that the results do not mean what they are purported to mean. I have read many personal accounts here and elsewhere of men who were able to eat a lot in their late teens, 20s, and early 30s, and then suddenly by their 30s gain a lot of weight despite not changing their lifestyle or diet much.
Inactivity alone does not explain it. Consider for example Bill Gate...according to his resume, in which he lists his precise height and weight, in his 20s he weighed just 125 pounds. It's evident he has put on a lot of weight, all in his mid-section, well before he turned 60. His job literally entailed sitting at a computer all day coding. If anything, given his philanthropy efforts and retirement, he is more active now than he was in his 20s when working full-time at Microsoft. Is he eating more? I doubt it.
For so many people, celebrities for example, a switch is flipped in which there is sudden weight gain after the age of 30 or so, like John Travolta, Stevie Wonder and others. Because celebrities are photographed, you can see the weight progression and the abrupt jump in weight. Even with money for personal chefs and trainers, not gaining weight is hard.
I can personally attest that if I ate the same quantity of food now as I did at 20 I would gain weight, and no I'm not 60. And I am just as active , maybe more so. So yeah not buying this study.
> Is he eating more? I doubt it.
So, four paragraphs all based on this assumption.
Why couldn't it be the case that a 20yo obsessive computer nerd eats less than a lavish billionaire?
[dead]
What's the age at which anti-aging interventions are most impactful?
I assume they don't help much when you're young, because you're already healthy as a youth.
Presumably waiting until you're on your deathbed to start high-intensity intervals is not the best idea either.
Supposing a person had a limited budget of "anti-aging firepower" in the form of pills, exercise, etc. -- what age would be most impactful to apply it?
That is way too complex a question to answer here. If you really want to dig into it including exercise, nutrition, sleep, and medications then the new book "Outlive: The Science & Art of Longevity" by Dr. Peter Attia is a pretty good summary of what we currently know.
https://peterattiamd.com/outlive/
I wouldn't think of this from a limited budget perspective. Much of what you can do is cheap or free. It doesn't cost anything to go to sleep earlier.
This doesn't seem to line up anecdotally;
The first outlier I see is female health and PCOS, starting in mid 20s for women.
The next outlier I see is insulin resistance and pre and diabetes based metabolism decline.
From a hormone perspective, nose, ear, chin (femalr), and head hair seem to be going under significant change.
Mid 20s with when your lifestyle shift just starts to catch up to you.
You go from a more active young person that eats just enough to get back to hanging with friends to binge drinking in an instant. Then you go from that to a much lazier, snackier lifestyle of 9-5.
Yeah, people on the whole do get fatter in their 30s, but that’s very easily linkable to lifestyle.
This is caused from eating too much, not a decline in “metabolism”
So, the combination of the research and my anecdotes - and your response seems to be
That by our early 20s our metabolism has already slowed (sugary food, alcohol, precipitous drop in activity)
1 reply →
Insulin resistance and PCOS absolutely have effects on metabolism. It’s very well studied.
how many outliers or exceptions do you need before you can throw out the theory
This is interesting for me to see. For the longest while I was wondering why through my 40s and later I didn't seem to be hit with middle-aged weight gain, all while living my sedentary life in the computer chair. I wouldn't classify myself as average though, I've always had low heart rate/low blood pressure and low blood sugar. Swimming in salt-water is fun because I can float without much effort.
I did notice a decline in metabolism/muscle mass in the past several years, so I took to walking rather than driving in the city/neighbourhood and eating more and regularly which seems to have brought my levels back up somewhat. Now I look like someone who only goes to the gym on leg days.
This was completely expected, at the macro level this is easily observed by measuring the outputs of metabolism and bodily function, mainly heat and physical activity. All humans have a baseline bodily temperature, meaning that the inner metabolism also is the same across all humans.
Sweating at different rates, surface blood vessel dilation including in your lungs, all change the flux. Having longer hair or wearing warmer clothing can too and can be balanced by those other things. Activity also gets balanced by those things. Eating cold food and drink vs warm etc.
That we maintain a baseline temperature doesn't tell you that metabolism alone is all that regulates it, there are other factors.
Your body can change the temperature gradient near its surface to retain or expel heat without a change in metabolism.
metabolism varies greatly controlling for height, activity level, and weight . sometimes as much as 600 kcal /day
"Humans are spherical cows"