Some years ago, one of my colleagues mentioned at the lunch table, "I went hiking this weekend, and man, my backpack was so heavy. I weighed it, and it was like 35 pounds. And then I realized, wait a second, I'm overweight by 35 pounds. I'm carrying this heavy backpack all the time!"
Thus began a collective weight loss competition we called Weight Gain 4000, named after an episode of South Park which had aired recently. ("I'm not fat; I'm big-boned!") I set up a Web page where people could enter their current weight, and it charted everyone's pounds over target weight as a function of time. Oh, and the goal was to lose weight, not gain it.
It so happened that I won this little competition with the aid of some extra bike rides. Then again, I also had the least amount of weight to lose. And my colleagues accused me of cheating because I managed to accelerate my weight loss as the deadline approached. (But I didn't cheat, honest!)
I was reminded of this competition from years ago when I read about John Dirks and Adam Orkand who also learned that an effective way to make you stick to your weight loss plan is to make a wager out of it.