The common mistakes people make to lose weight section is decent, however I felt it was lacking. People make a lot more than just 3 common mistakes, which are crash dieting, too much exercise and checking weight too often. I'd like to see this section more fully covered because a better understanding of why these are bad, as well as other mistakes that weren't even mentioned, are going to help people make better choices in the future. Overall this is an important section that was sort of glossed over.
In the section on why people become obese it mentions eating too much, sedentary lifestyle, and not sleeping enough. While I won't deny these are all reasons for an increase in weight, it fails to also mention medical conditions and medications. These are both areas that should not be left out and it seems this book was only targeted at people to try to make them feel bad about their weight gain so they'll want to lose weight. (which by the way is not a good technique of motivation, which is one of the things the book promises to provide). The thing is, while yes many factors leading up to obesity are based on our own habits and behaviors and if we want to lose weight we have to take responsibility for those. That's absolutely true. But I feel like this book is so caught up in that area that it's forgetting to share the entire story.
An effective reward is something that is desirable, timely, and dependent on meeting your goal. The rewards you choose may be material (e.g., a movie or music CD, or a payment toward buying a more costly item) or an act of self-kindness (e.g., an afternoon off from work or just an hour of quiet time away from family). Frequent small rewards, earned for meeting smaller goals, are more effective than bigger rewards that require a long, difficult effort.