If you are one out of three Americans, you are clinically obese and hopefully looking to make a change. But are you looking in the right places? It can be difficult to tell. In 2014, weight-loss programs were a 2.5 billion dollar business. The companies behind them make a lot of claims about how great you’ll look after buying their product or using their program. You don’t have to take their word for it. Let’s look at what the science says.

Researchers at Johns Hopkins University set out to review over 4,200 weight-loss studies for the purpose of answering your big question: does my diet plan actually work?

In order to be chosen, a study had to run at least 12 weeks. It had to be randomized and controlled meaning participants were broken into two groups: one group using the weight-loss plan and another group eating their normal diet for control. Only 39 studies met these basic standards. They covered 11 weight-loss programs.

The researchers determined that Weight Watchers and Jenny Craig were the only plans backed by randomized controlled trials that showed weight loss over a year’s time. That’s it. Just two.

The NutriSystem plan also showed more weight loss over just a three month period when compared to the control group, but further study is needed. Co-author Dr. Jeanne Clark explained that “those benefits are long-term goals; losing weight for three months, then regaining it, has limited health benefits. That’s why it’s important to have studies that look at weight loss at 12 months and beyond.”

If you’re concerned with choosing a weight-loss plan whose effectiveness stands up to the rigors of scientific testing, your best (and only) bets are Weight Watchers and Jenny Craig.

Regulation or a lack thereof

Nearly every weight-loss program on the market is not backed by reliable science. But how can that be?

Believe it or not a weight-loss company has no responsibility to provide scientific backing for their product or plan. Yes, that’s right, they are not required to scientifically show that their product works.

When it comes weight-loss supplements, the Food and Drug Administration would like to remind everyone that “under the Federal Food, Drug and Cosmetics Act (as amended by the Dietary Supplement Health and Education Act of 1994), dietary supplement firms do not need FDA approval prior to marketing their products. It is the company’s responsibility to make sure its products are safe and that any claims made about such products are true.” Nice, huh.

Research

Their findings were published in the Annals of Internal Medicine, titled “Efficacy of Commercial Weight-Loss Programs: An Updated Systematic Review.”