Oh, and before I forget--let me just point out that stress, especially chronic stress, is a huge factor in weight gain, to the point that one of the existing models for obesity in rats is stress-induced hyperphagia. I cannot overestimate how much energy balance and stress are hooked together (as are things like reproductive investment and social context). I would be very interested in looking at overall stress levels in the context of modern weight gain, personally.

In the meantime, I'm looking at the interactions between cortisol and leptin in the context of social behavior, and I'm really excited to see that data once I can successfully analyze it.