| Sure there are plenty of undigested elements that inevitably become waste products, but if it's food that most people are eating, I'm very unconvinced that calories in minus calories out isn't the first order effect to model. It's difficult for me to find nutritional data for grass clippings; but let's take your example and compare coke to alfalfa sprouts for grass clippings: * 100g alfalfa sprouts is ~23 calories and would occupy a volume of ~3 cups [0] * 100g of coke is ~38 calories and occupies a volume of ~.4 cup [1,2,3] If you wanted to eat enough alpha sprouts to be equivalent to that .4 cup of coke, you would need to eat almost 5 cups worth, ~12x more volume! I can't imagine eating 5 cups of alfalfa sprouts, but half a cup of coke is trivial to guzzle. Relative energy density seems to limit caloric consumption far before we need to model undigested bits. [0] https://g.co/kgs/8aUo7E [1] http://www.coca-colaproductfacts.com/en/coca-cola-products/c... [2] http://chemistry.elmhurst.edu/vchembook/121Adensitycoke.html [3] http://depts.washington.edu/chem/facilserv/lecturedemo/Densi... |