My buddy just told me he was sending his bow back to get different cams, to reduce the let off to 65% (I think he said it was 80% now).

Any way, I asked him why.
He said somebody told him he would get more energy with a lower let off. Is this correct? Let off is dictated by what.... the shape of the cam? If the draw length and wieght is the same, how can it give you more enegy?
I'm technically challenged when it comes to archery. So take it easy on me.