Carbohydrates Provide 4 Times less ATP than Fats

ATP is an energy unit produced by mitochondria.

Carbohydrates make 4 times less ATP than fats.

1 mole of glucose gives you 36 ATP units

1 mole of stearic acid (sat fat) 147 ATP units

So it makes sense then that in nature you would eat differently when the sun is strong vs. when the sun is weak.

In summer with a strong UV and infrared light you can make ATP from the sun even with no food present.

In winter the photoelectric effect goes down, so you mainly eat foods with high electron density - animal protein and fat.