Re: leptin/test
I wish that bodybuilder study you reference would have taken a look at estradiol levels. Really their testosterone was still well within normal range. And while the cellular mechanisms do suggest a resulting decrease in testosterone I have a feeling the libido issue has more to do with an altered test/estrogen ratios than anything.
Put simply less test equals less aromatization. Less bodyfat equals less aromatase enzyme. Overall a greater net fall in E2. Sort of like the letro libido killing effect.