A Randomized Controlled Trial that used lotteries to encourage weight loss. Very well designed in terms of behavioral principles. In the treatment group, a person steps on the scales in the morning. The subject’s weight is calculated & sent to a server comparing it to his weight-loss goals. The subject receives an email about his weight and a text message regarding the daily lottery. Success in meeting weight-goals enters the subject into a daily lottery with a 20% chance of winning $10 & a 1% chance of $100. If one doesn’t meet their goal, they are still entered in the lottery. But if they win, they are notified by text what they could have won, a clever use of regret aversion as motivational tool.