How are some foods more caloric dense than other foods?

Question

How are some foods more caloric dense than other foods?

In: Chemistry

Answer 1

Calories are a measure of *what your body can digest*.

You can’t digest cellulose, so most plant fibers are 0 calories for you (but the sugars and juices in fruits and vegetables are caloric, even if the “fibers” in fruits and vegetables aren’t). Some animals (cows for example) can digest cellulose, so grass is very caloric for them.

Your cells use sugar for energy, and various vitamins, minerals, and proteins to “function”, so the foods that can easily be converted to sugar are very caloric. Anything that’s sweet, obviously, but also anything that’s starchy (starch is a long string of sugars), so bread, potatoes, etc.