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> But the idea that thermodynamics do not govern 85% It does govern 100%, in a technically useless sense. If it was just thermodynamics, you'd be able to drin

by beagle3 12y ago

> But the idea that thermodynamics do not govern 85% It does govern 100%, in a technically useless sense. If it was just thermodynamics, you'd be able to drink hydrocarbons (e.g. gasoline) for food. In a bomb calorimeter, it's as good as carbs or fat, only denser. Or you'd just eat wood or paper. Cellulose is, after all, a carbohydrate! But it's not that simple. - See e.g. this article: http://www.princeton.edu/main/news/archive/S26/91/22K07/index.xml?section=topstories http://www.princeton.edu/main/news/archive/S26/91/22K07/inde... - It does not mention control for "calories out", but assuming rats just do what rats do - it indicates that food composition goes much deeper than calorie intake. - some cells some time use fermentation instead of oxidation, which gets much less energy from food (about 1/6 if I recall correctly). Mostly in tumors, but not only in them. - Some people can apparently get ~2kcal/gr from fiber carbs, where others cannot. People of Japanese origin, in particular, http://www.nature.com/news/2010/100407/full/news.2010.169.html http://www.nature.com/news/2010/100407/full/news.2010.169.ht... - but this is just the most studied example, not the only one. - Atwater factors, which everyone uses to estimate intake often based on 100 year old tables, are horribly inaccurate, e.g. http://www.ncbi.nlm.nih.gov/pubmed/18065582 http://www.ncbi.nlm.nih.gov/pubmed/18065582 (4%-11% error) http://www.ncbi.nlm.nih.gov/pubmed/22760558 http://www.ncbi.nlm.nih.gov/pubmed/22760558 (32% error) - Actual digestion processes depend on enzyme availability, the supply of which lags demand by up to 3 weeks (and tails by up to 6 months), and apparently depends nontrivially on olfactory clues whereas most models assume everything about nutrition and digestion is static. e.g, if you start daily drinking of a gallon of fat you haven't had in the last 6 months, you're going to put most of it out in the bathroom until your body ramps up production of some relevant enzymes, which can take a few days and up to 3 weeks. - Simple stated, "a calorie is a calorie" violates the second law of thermodynamics. See http://www.ncbi.nlm.nih.gov/pmc/articles/PMC506782/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC506782/ ; It's not from Richard P. Feynman - it's from a Richard D Feinman, btw. So, yes, thermodynamics reigns supreme but your ability to estimate your actual calorie intake is very crude. Similarly for your expenditure. The result being, two people can basically eat the same food and do the same kind of activity, and still have significantly different energy balance.

JoeAltmaier 12y ago
Assuming all that. It is still 100% true that any subject who consumes less food than they did before, will intake fewer calories and lose weight.
- crazygringo 12y ago
  Um, no, it's not. If the amount of calories you burn decreases more than the calories they intake, for example, you might not lose weight. You might even gain weight. And that's the point -- calories burned is not a constant. It changes a great deal, and it's very common for the body to respond to less calories in, by burning less calories.
  - JoeAltmaier 12y ago
    To test the truth, try the converse. If you eat more, will you gain weight? Most of us would agree this is an obvious truism. Or take the limit. If you eat nothing, will you lose weight? Obviously you will. The question exists because folks want to eat as much as they can, and also lose weight. Give in to thermodynamics, eat very little, and lose weight as quickly as you like. That's chemistry and physics right there.
    - crazygringo 12y ago
      Again, nope. If you're ~50 lbs overweight, and then cut out starches and sugars, replacing them with protein and fat, but increase your overall calorie intake slightly, there's still a good chance you will lose weight. So, not an obvious truism, but actually incorrect.
      - JoeAltmaier 12y ago
        What was that in response to? Did you post to the wrong comment? I'm confused.
- beagle3 12y ago
  > "less food" But that is true only if it is proportionally less food (that is, 15% less would mean exactly 15% less of everything). Any variation would mean that it is not 100% true: If you eat 2kg less lettuce but eat 0.5kg more fat, you're eating "less", but taking in more energy (whether you use it or not is a completely different issue ...) And if you replace your food with calorie sparse food, you can eat "more food" but take in less calories. How much calories you will actually keep or use, rather than throw out is a different question. Thus, your statement of 100% truth is wrong, and logically useless, even if practically it is mostly useful.

by beagle3 12y ago

JoeAltmaier 12y ago

Assuming all that. It is still 100% true that any subject who consumes less food than they did before, will intake fewer calories and lose weight.

crazygringo 12y ago
Um, no, it's not. If the amount of calories you burn decreases more than the calories they intake, for example, you might not lose weight. You might even gain weight. And that's the point -- calories burned is not a constant. It changes a great deal, and it's very common for the body to respond to less calories in, by burning less calories.
- JoeAltmaier 12y ago
  To test the truth, try the converse. If you eat more, will you gain weight? Most of us would agree this is an obvious truism. Or take the limit. If you eat nothing, will you lose weight? Obviously you will. The question exists because folks want to eat as much as they can, and also lose weight. Give in to thermodynamics, eat very little, and lose weight as quickly as you like. That's chemistry and physics right there.
  - crazygringo 12y ago
    Again, nope. If you're ~50 lbs overweight, and then cut out starches and sugars, replacing them with protein and fat, but increase your overall calorie intake slightly, there's still a good chance you will lose weight. So, not an obvious truism, but actually incorrect.
    - JoeAltmaier 12y ago
      What was that in response to? Did you post to the wrong comment? I'm confused.
beagle3 12y ago
> "less food" But that is true only if it is proportionally less food (that is, 15% less would mean exactly 15% less of everything). Any variation would mean that it is not 100% true: If you eat 2kg less lettuce but eat 0.5kg more fat, you're eating "less", but taking in more energy (whether you use it or not is a completely different issue ...) And if you replace your food with calorie sparse food, you can eat "more food" but take in less calories. How much calories you will actually keep or use, rather than throw out is a different question. Thus, your statement of 100% truth is wrong, and logically useless, even if practically it is mostly useful.