The trouble with this subject is that everybody, including commenters in this thread, thinks they already know what the solution is, even before they have a good grasp of the problem.

I recommend reading Gary Taubes ("Good Calories, Bad Calories", "Why We Get Fat"), not because of what he thinks that the solution is, but to understand the range of facts that a theory of obesity must explain.

When Taubes starts to promote his own theory (carbs are bad, fats aren't, exercise is fairly useless, insulin is very important), he may or may not be right. Nevertheless his book is invaluable for learning about the extremely counter-intuitive facts of obesity.

To name a few: - obese 6-month old babies - morbidly obese mice starving to death - obesity epidemics among native americans in 19th century - lack of obesity among all animals - prisoners on a forced 10K calorie diet barely gaining weight

We won't conquer the obesity problem until we start treating it as a huge, extremely complicated mystery to be solved, instead of as a problem of persuasion, where the solution is to convince other people that you have the obvious answer.