[_Adam]

Dietary calories are actually kilocalories. 2500 kcal is approximately 3kWh..enough to run a thousand phones for an hour.

What's impressive isn't the efficiency of the body's use of energy (electric motors are already pretty good) , but rather how efficiently it extracts and stores it.

If smartphones had our stomachs, we wouldn't need to charge them..just let throw a hamburger in there once a month.