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Comment by greglindahl | Hacker News Reader

What you missed out on is feedback loops that affect your basal metabolism. So: eat less, your body decides it is starving and reduces your basal metabolism, you continue to eat less (better-than average willpower!), and... you gain weight.

I'm a physicist, and I roll my eyes whenever anyone starts up with simplistic arguments about humans, food, and thermodynamics. Thermodynamics holds, but the system doesn't work the way you think it does.

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Can your body just "reduce your basal metabolism"? Where are the energy savings? Is your body temperature lowered? I'm skeptical of the idea that differences in "metabolism" can account for different results arising from the same energy inputs.

Yes, your body temperature can be lowered, somewhat. Your temperature actually varies over a pretty wide range all of the time, with daily cycles and in response with your activities and things like fighting infections. But your average temperature can trend higher or lower, corresponding to a higher or lower basal metabolism.

Other things that can happen when your metabolism slows down are that you get tired more often and more easily, your thought processes slow down, you sleep more. This happens to everyone as they age, and it can also happen from chronic stress, calorie restriction sufficient to trigger 'starvation mode', and anything else that causes your body to try to conserve energy for survival.

What can be done to boost basal metabolism? A safer DNP? The current approach, diet and exercise, although it may work in individual cases, is not effective at the scale of public health.

Why, yes, it's a typical confounding situation with exercise and diets. As you probably know, it's difficult to do calorimetry on humans, but if I recall correctly it is partly lowered heat generation (which doesn't necessarily change the core temperature you measure with a thermometer) and moving around less.

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