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You're correct. I should been clearer. I meant "energy" in terms of energy the body can use. E=MC^2 means everything can be considered energy. But can somethin

You're correct. I should been clearer. I meant "energy" in terms of energy the body can use. E=MC^2 means everything can be considered energy. But can something be used as energy for a specific process, like making a body fatter, is another issue. We agree, calories do not measure how much energy the body can extract or use from a piece of food. They only measure how much energy is produced burning the food. Bodies don't burn food, they digest it. So measuring calories doesn't say anything about whether a particular substance can be used by the body.

beagle3 14y ago
> They only measure how much energy is produced burning the food. Bodies don't burn food, they digest it. You need to review your biology. The most common energy extraction process in the body actually IS, at its essence, oxidation - a.k.a "burning". And that's why people did the calorimeter burning measurements. The other common process is essentially fermentation, but in a healthy human, the vast majority of energy is obtained from food through oxidation. > So measuring calories doesn't say anything about whether a particular substance can be used by the body. It puts an upper limit because (as far as we know) oxidation is the most efficient process the body uses, but not a lower limit. The body may flush out anything without any form of digestion, fat conversion, or oxidation (thus no energy extraction), even if it is pure sugar. Furthermore, the enzymes used by the body for oxidation are very specific. The most abundant carbohydrate around us, cellulose (wood and paper are examples), cannot be digested / oxidized / burned by the human body.