Here is a thought-provoking article, summarizing the obesity research over the last few decades:
So, in reality, despite the short-term effectiveness of certain diet regimes, the most common outcome of dieting itself, by a landslide, is either weight regain or trivial weight loss — which leads to a lot of repeat business for companies like Weight Watchers. But no diet, not even Weight Watchers, can claim that more than a small minority of its customers successfully keep the weight off in the long term. To be fair, Weight Watchers doesn’t explicitly promise long-term weight loss, but it neglects to mention that it’s extremely unlikely and instead makes vague claims on its website, such as, “Our proven program works.” Works for what? It would be easy for potential customers to misconstrue the website’s statement that they’ve “helped millions of people change their relationship with food for good.”
The problem is that dieting itself leads to a host of physiological changes that undermine long-term efforts to maintain the weight loss.
Check out the rest of the article: Oprah’s Investment in Weight Watchers Was Smart Because the Program Doesn’t Work