One word: incentives. Something that makes people do things they would otherwise not do. If you believe that incentives can work, you have to admit that sometim

One word: incentives. Something that makes people do things they would otherwise not do. If you believe that incentives can work, you have to admit that sometimes even otherwise healthy people may not be in control of their weight. Sometimes those incentives turn into outright addictions. It's easy to say that people can overcome their addictions by sheer willpower. But if you believe that you can learn something about the world by observing it (as opposed to using pure reason), it seems plausible that many people don't have such willpower. And sometimes obesity is a symptom of a disease.