Comment by Xcelerate

The article seems to miss what is (at least to me) the most interesting follow-up question: if exercise doesn’t cause a person to burn significantly more Calories throughout the day to induce weight loss, then what does?

I’m somewhat hard-pressed to believe the answer is diet alone. Anecdotally, when I was running 100 miles per week in college for cross country, I ate three or four giant meals per day and maintained a very low weight. Ten years later, I have an injury that makes most types of exercise difficult, and I’ve observed that I really can’t eat more than one meal per day (dinner), otherwise my weight starts to creep up.

I find it odd that Calories are used in relation to weight gain, because (kilo)calories are a unit of energy, and excess weight is due to excess fat. Is there a simple linear relationship between the extractable energy content in food (as determined by the Atwater system) and the conversion of food components into fat by the digestive system? I find that hard to believe. Shouldn’t we be using a mass balance rather than an energy balance? If you could observe digestion at the atomic level, you would simply quantify which atoms from food end up in fat stores and which leave the body via other processes. Presumably, these atoms could then be bucketed into source categories (e.g. certain types of proteins or carbohydrates). I wouldn’t be surprised if exercise somehow alters the fat accumulation process even if it doesn’t significantly affect human metabolism.