And people don't just go back to their old ways once the two weeks are over?
In the second phase—the "Live it!" phase—you take those habits and transition into a permanent lifestyle program. That's where the slow and steady part comes in. But perhaps that initial behavior change might be motivating for the long run. Will people continue to [follow all the rules] long term? No—but perhaps more so than if they just eased into a plan. Many people say, "I didn't realize I was capable of making these changes." So for the two weeks they'll have no snacks except for vegetables and fruits, and then they're much more aware [of their snack habits].
Is there one behavioral key to losing weight?
People do know they need to eat less and exercise more; they just can't put it into practice. There are a tremendous number of things [influencing lifestyle behaviors]: what we grew up with, what our brain tells us, what our stomach tells us, our habits. If all these things influence what we eat and how we move, the challenges that we experience are similarly diverse. For one person, it may be more about physical activity than diet. For another, it's about not skipping breakfast and being ravenous later on. People need simple, practical advice on what to do about these things.