“Lose weight NOW”, “You’ll never believe how [this person] got slim”, “An easy way to lose extra pounds” – big claims, with little to back them up. Diets and weight loss programs are popping everywhere nowadays, and they’ve done so for years and years, but does the science actually back them up? Kimberly Gudzune, an assistant professor of medicine at Johns Hopkins found that many diet plans have zero or very little rigorous scientific evidence backing them up.

Image via the Weight Lose.

Exercising/running regularly, and having a healthy and balanced diet are the best ways to lose weight, but when it comes to figuring out which diet and weight loss plan work best, things get very fuzzy. Even physicians are at a loss – because there’s basically no solid scientific info on which option works best.

Gudzune wanted to remove the fuzziness and uncertainty, and analyzed most popular diets and weight loss options.

“Weight Watchers and Jenny Craig are the two programs that have the evidence to support that they help people lose weight and keep it off,” she explained. “For the other diet programs [there’s an] absence of evidence. We don’t know whether they help people to lose weight and keep it off.”

The first thing they foun was that there were actually quite few studies that rigorously tracked how people lost weight – and if they maintained the new weight. Sure, there was a trove of studies on the issue (they found no less than 4,212), but only a small fraction of those (45) actually followed the golden standard of modern medicine – randomly assigning people to a weight loss program or not, and then tracking their evolution over time.

“The majority [of programs] still have no rigorous trials done,” says Gudzune.

According to her analysis, only Weight Watchers and Jenny Craig helped dieters to lose weight and keep it off for at least a year. Other programs, such as Atkins, the Biggest Loser Club and eDiets also helped people drop pounds, but they only followed the progress of the users for 3-6 months – so there’s no way to know if the weight was maintained or not.

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People lost on average between 3% and 5% of their weight using these two programs – which may not seem like much, but it’s certainly a step in the right direction, and a solid step at that one.


“Even that small amount of weight loss can help to lower blood sugar, improve cholesterol profiles, help to lower blood pressure and ultimately prevent things like diabetes,” she says.

More would be better, but a 5% loss is not two times worse than a 10% loss, actually

“Would 6% or 8% or 10% of body weight lost be better? Yes, but it’s not like the interaction is totally linear,” says Gary Foster, chief scientific officer of Weight Watchers International.

But people spend money (and lots of it), in the hope of dropping many pounds and reaching an ideal weight – are these results actually enough?

“Entering any weight-loss program, people come in with idea of losing large amounts of weight,” Gudzune said. “It’s not impossible to do, but it’s the more unusual occurrence.” She noted that in 2014, Weight Watchers cost about $43 a month, while Jenny Craig was $570 a month — the latter being more expensive because it involves food for the month.

Is spending tens or hundreds of dollars a month actually worth it? The answer is likely no. Basically, it’s not about the diet you keep, it’s not about a specific nutrition plan; it’s about dedicating yourself to a decent calorie intake, a balanced nutrition, and working out or walking/running as often as possible. Dr. Yoni Freedhoff, an Ottawa-based obesity doctor — who has worked with thousands of overweight and obese patients — says he tells people:

“Ultimately you need to like the life you’re living food-wise if you’re going to keep living that way. It’s crazy to think, with billions of people on the planet, that there’s one approach that suits everybody.” He added: “The best diet for one individual is the worst diet for another individual.”

Which brings us to the next question – how does a multi-billion industry thrive, without actually having the science to  back it up? How do people get away with promoting one lifestyle as the best one, when there clearly is no one best lifestyle? Hey, and if it actually works like they claim it does, then why are there no solid studies to back it up? That probably has a lot to do with the fact that people often believe what they want to believe – even when there’s not enough evidence. People want a quick fix to a complicated problem. By all accounts, weight loss is not something you can sustainably do fast. It’s a lengthy process. The best diet, the best weigh-loss program is the one you stick to.

Journal Reference: Kimberly A. Gudzune et al. Efficacy of Commercial Weight-Loss Programs: An Updated Systematic Review. Ann Intern Med. 2015;162(7):501-512. doi:10.7326/M14-2238