Comment by oijkuij
1 year ago
One possibility: we have been collecting learning to use our feet less throughout life.
"In 1969, 48 percent of children 5 to 14 years of age usually walked or bicycled to school (The National Center for Safe Routes to School, 2011). In 2009, 13 percent of children 5 to 14 years of age usually walked or bicycled to school (National Center, 2011). In 1969, 41 percent of children in grades K–8 lived within one mile of school; 89 percent of these children usually walked or bicycled to school (U.S. Department of Transportation [USDOT], 1972). In 2009, 31 percent of children in grades K–8 lived within one mile of school; 35 percent of these children usually walked or bicycled to school (National Center, 2011)."
[Source](http://guide.saferoutesinfo.org/introduction/the_decline_of_...)
The amount of calories burnt through exercise is completely negligible. For instance running a mile at a good pace will generally burn around 100 calories, the same as you get from eating about one banana, or about drinking about half a bottle of Coke.
Exercise does have many positive metabolic and other benefits, but not anywhere enough to be a causal explanation on its own. If people started walking 5 miles a day, every day, not only would there still almost certainly be a widespread and growing obesity epidemic, but there's even an argument that it could be worse. Increases in activity tend to drive increases in hunger which will typically surpass caloric deficits if somebody is not actively controlling their diet, in which case they would not be fat in the first place.
This is made even worse by misleading advertising which will do things like showing fit athletes drinking Gatorade, Coke, etc during their training or competition. And somebody goes and does a couple of miles on a training bike and does the same thing - which is going to send their net caloric input skyrocketing.
I can regulate my weight by doing sports regularly or not with zero conscious attempts to change what I eat. And yes, non sports like taking daily walks have measurable effects too on me.
People who stop doing sports suddenly gain weight. People who get into sports habit like running or swimming slowly loose weight.
So, imo, this uber simplified model of just don't work like that.
Exercise does more than just use calories, it also changes blood glucose profiles, and I suspect lots of other metabolic things too, given how impactful it is on general health. It's distinctly plausible those things influence weight.
Proper physical activity burns a lot of calories, especially when its cold. It also changes some metabolic components, so not just the burning alone has an effect. It will not necessarily lead to hunger surpassing calorific deficits (and at very high activity it isn't even possible to eat enough to cover the deficit).
On the other hand, 50 calories x 365 days a year x 20 years x 5,000 calories per lb of weight = 75 lb of additional weight.
> Increases in activity tend to drive increases in hunger As far as I know, certain types of high intensity exercise do so but not necessarily all exercise.
I'm not fond of the calories/lb calculations because everything's really relative to where your caloric equilibrium point is, but this is an aside. Let's take your numbers at face value, and now consider that in 1970 the average American was eating 2,025 calories. Whereas by 2010 we were up to 2,481 [1] - a total increase of 456 calories/day!
If we take your numbers at face value, that'd be a delta of 684 pounds per 20 years. Again kind of an obvious indicator why these long term calorie/pound measurements are pretty dubious, but at the same time also an indicator of why diet is just so much more important than exercise for weight management.
[1] - https://www.pewresearch.org/short-reads/2016/12/13/whats-on-...
Yeah, I always get a bit amused when people point to one sole food or environmental issue ("microplastics!" says one comment) to blame for the obesity epidemic, when there are two glaringly obvious pieces of data:
1. As another commenter posted, total calories consumed per capita has gone up considerably since 1970.
2. As you posted, we move a lot less than we used to. There are tons of studies that confirm this across a number of different metrics (e.g. average grip strength has gone down considerably since the 80s, https://www.npr.org/sections/health-shots/2016/06/13/4815909... ).
We eat a lot more, of more foods that have higher calorie-to-nutrient ratios than we used to, and we move a heck of a lot less.
Yeah I'd believe a stronger sedentary lifestyle is the biggest factor in the waste line stagnation if the diet is not the same. They did not have omnipresent smartphones in 1970.
Heck, back in my days, we kids at least had to walk to each other's house to play video games together.
I wonder how jobs have changed too. I started gaining weight when I switched from a delivery job to a lab job.