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People spend far too much time discussing the specifics, like glucose vs. fructose. Then they eat 8500 kcal/day but eat the "right" sugar and they're supposedly

People spend far too much time discussing the specifics, like glucose vs. fructose. Then they eat 8500 kcal/day but eat the "right" sugar and they're supposedly healthy. It's easier to care about fancy things rather than the basics. Physics dominates everything, first and foremost. Thermodynamics governs diet through energy conservation laws that run the universe. That's rule #0. Everything else is maybe 20%. Human biology does not trump the laws of nature.

rand_r 9y ago
Physics dominates, but it’s often too simple a model to be useful in diet planning. When you run things through the filter of the an incomprehensible machine like the Human brain and metabolic and hormonal pathways the system gets much more complicated and useful. The non-caloric fibre content of food is vital to gut flora, whose importance we’re still discovering. Different foods affect hunger differently. High fat foods are more satiating that sugar. The body isn’t a bucket, it’s a donut which has the capacity to absorb some food through internal walls while the food slips through very slowly. If you drink a bottle of oil, you won’t get fat. You’ll just have very runny and uncomfortable stool for a while.
reureu 9y ago
Our body functions predominantly on ATP, not on glucose or fructose or fat or protein. ATP gets generated from those other macromolecules in pretty complicated biochemistry. You're definitely right that thermodynamics governs everything, but it governs it at the ATP level and not at the macronutrient level. Those additional layers of abstraction distort the whole calories in-calories out math. Eating the "right" thing is more important than eating the "right" number. Consider eating 800 calories of protein versus 800 calories of alcohol (also technically a macronutrient). You're going to metabolize each differently, and you'll probably feel better eating the former than the latter. This is obviously an extreme example, but the point is that things that you eat affect your body in ways beyond that magic calorie number.
- Tharkun 9y ago
  I can assure you, I feel a lot better after 800kcal worth of alcohol (about 3 beers) than after 800g of protein (a small chicken).

rand_r 9y ago

Physics dominates, but it’s often too simple a model to be useful in diet planning. When you run things through the filter of the an incomprehensible machine like the Human brain and metabolic and hormonal pathways the system gets much more complicated and useful. The non-caloric fibre content of food is vital to gut flora, whose importance we’re still discovering. Different foods affect hunger differently. High fat foods are more satiating that sugar. The body isn’t a bucket, it’s a donut which has the capacity to absorb some food through internal walls while the food slips through very slowly. If you drink a bottle of oil, you won’t get fat. You’ll just have very runny and uncomfortable stool for a while.

reureu 9y ago

Our body functions predominantly on ATP, not on glucose or fructose or fat or protein. ATP gets generated from those other macromolecules in pretty complicated biochemistry. You're definitely right that thermodynamics governs everything, but it governs it at the ATP level and not at the macronutrient level. Those additional layers of abstraction distort the whole calories in-calories out math. Eating the "right" thing is more important than eating the "right" number. Consider eating 800 calories of protein versus 800 calories of alcohol (also technically a macronutrient). You're going to metabolize each differently, and you'll probably feel better eating the former than the latter. This is obviously an extreme example, but the point is that things that you eat affect your body in ways beyond that magic calorie number.

Tharkun 9y ago
I can assure you, I feel a lot better after 800kcal worth of alcohol (about 3 beers) than after 800g of protein (a small chicken).