Humans have always eaten carbs; it’s the body’s preferred energy source. But human bodies can get energy from three sources, in order of preference—carbs, fat, and muscle (when all else fails).

Our bodies evolved to store fat for this very reason—future energy needs. Ancient humans lived feast or famine, and our biology adapted. We’re built to fast for days, using body fat for energy. When carbs are available, they’re preferred because they are faster and easier to burn.

Sugar is carbs. But ancient fruit in no way resembles today’s cultivated monstrosities, in appearance or sugar content.

Our modern problem is—we gorge on carbs all day long. So our body helpfully stores the excess as body fat for future use—because it expects eventual ‘famine’ where we’ll be fasting with few carbs available and need it. But we never let our body get to burn that fat.

To nitpick: at rest, muscle cells use fat over carbs to produce ATP. It is only during effort that the cells start to use more carbs than fat. The rest of the post is, to my understanding, correct.

Body’s preferred food source is ketones. It functions most optimally when using ketones.

But the fastest accessible energy source is glycogen, which comes from carbs.