Ruining your life and all your meaningful relationships once a month will keep you slim. Or at least it will if stress and embarrassment make you lose your appetite. I am always my thinnest when I'm at my most stressed out - pledging, switching jobs, being broken up with... I can't say there's much motivation to maintain a happy existence since I look awesome when I'm miserable.
With the exception of my first year out of college, when I was really stressed out, then gained a lot of weight, and then ended up even more miserable, I'm not hungry when faced with stressful situations. After that year I realized how large I had gotten, became desperately miserable, started ruining my life, and while everything else pretty much sucked, I lost 20 lbs.
Lately I've been panicking about situations that shouldn't be that big of a deal. I can't explain why this is happening, but today I wasn't hungry. At all. Happy people are fat, and I just might be crazy.