[unoti]

I think it's actually different for different people. My understanding is that someone with a high body fat percent can sustain quite a bit of an exercise regimen for a while with low carbs, consuming their fat for energy. But eventually as their body fat percent comes down, they'll need to supplement their diet with carbs to maintain their energy level for the same exercise.

The P90X diet program is based on this idea, with 3 phases of the diet with very low carbs in the first phase, medium carbs in the second phase, and more carbs in the third phase.

So maybe you're both right...