Food is energy. Calories are simply a measurement for a unit of energy.

Therefore we should be eating food that is the easiest for our body to convert from a particle of food into a particle of energy.

We exhale, trees/bushes use our carbon dioxide and sunlight, convert it into sugars to feed themselves. They then produce fruit, vegetables with that energy.

The obvious conclusion is for us to then eat the fruit and veggies and through our breath and poop we complete this never ending cycle of back and forth between us and trees… air, food, reciprocated eternally.

We are natural vegetarians?