Well, here's a source I was remembering the claim from (I was just a little off):
http://www.slate.com/articles/health_and_science/medical_exa...> In reality, 97 percent of dieters regain everything they lost and then some within three years. Obesity research fails to reflect this truth because it rarely follows people for more than 18 months. This makes most weight-loss studies disingenuous at best and downright deceptive at worst.
I also think this article is interesting because it includes some personal testimony from a successful long-term dieter that I think illustrates why most people are not successful:
> Debra Sapp-Yarwood, a fiftysomething from Kansas City, Missouri, who’s studying to be a hospital chaplain, is one of the three percenters, the select few who have lost a chunk of weight and kept it off. She dropped 55 pounds 11 years ago, and maintains her new weight with a diet and exercise routine most people would find unsustainable: She eats 1,800 calories a day—no more than 200 in carbs—and has learned to put up with what she describes as “intrusive thoughts and food preoccupations.” She used to run for an hour a day, but after foot surgery she switched to her current routine: a 50-minute exercise video performed at twice the speed of the instructor, while wearing ankle weights and a weighted vest that add between 25 or 30 pounds to her small frame.
> “Maintaining weight loss is not a lifestyle,” she says. “It’s a job.” It’s a job that requires not just time, self-discipline, and energy—it also takes up a lot of mental real estate. People who maintain weight loss over the long term typically make it their top priority in life.