On Sunday, December 2, 2012 1:55:20 PM UTC-6, Doug Freyburger wrote:

Stay too low and in
various time frames two weeks to a year T3 then leptin then cortisol
levels interfere with benefits of lower carb.

I've seen that claim repeatedly on the web. But the only published studies I could find on it were mouse models. I even wrote to Jeff Volek (who wrote the most recent Atkins book) and he said

From: "Volek, Jeff"
Subject: Does Very Low Carb + Intense exercise cause Testosterone Drop?
Date: Nov 30, 2012 4:29 AM

Hi [Adam],

I have done a lot of work on testosterone, including its regulation by
diet. We have measured testosterone in many of our studies examining
effects of well formulated low carbohydrate diets and never observed a
decrease. In fact, a significant body of research indicates that low fat
diets are associated with lower testosterone, so if anything a higher fat
intake would protect against low testosterone.

Best,
Jeff Volek

I suspect that the key here is "WELL FORMULATED". Volek advocates a lot of careful minerals-management and he acknowledges that people who don't often either find the diets intolerable or get into trouble.
Still, if anybody has some good literature citations on the whole "low-carb + exercise = trouble(testosterone, cortisol)" thing, I'd be real interested.