I think it's actually a simple explanation that most people don't comprehend for obvious reasons: we all love to eat when we're upset. I LOVE JUNK FOOD when I'm really upset.

However, there are people who don't eat as a response to stress. It's the simple calories in/calories out equation: if you don't take calories in, but keep getting rid of calories, even if it's just by breathing, then you're going to lose weight.

I had a serious problem with depression in my early 20s when I was at Michigan State. There was a short while where I spent most of my time in bed, and a lot of time crying in the car. Well, I generally don't eat in bed, I sleep. I lost 20 pounds in a very short span of time.

I've gained it all back since then. Now, I'm a happy cyclist and loss of appetite is only an issue if I have tonsillitis like I did a couple weeks ago.