[1_player]

Carbs is not the only fuel. Fats can be used as well. Proteins too, in case of emergency.

The rule of thumb is proteins and fats are essential, carbs are not. How much of each is still up for debate.

[dnhz]

I'd just say that what's essential to eat (>50-60 g protein/day and a few grams of omega-3s) is different from what's optimal (what ratio of fat/carbs/protein).