Most Commercial Weight Loss Programs Aren’t Backed by Scientific Evidence, Study Says

The commercial weight loss industry has ballooned to an estimated worth of $2.5 billion, but few scientifically sound studies exist that prove the efficacy of these programs, a review of 4,200 related research papers reveals.

The report, published Monday in the journal Annals of Internal Medicine, found that among 32 popular commercial weight loss programs available in the U.S., only 11 have been studied using a randomized controlled trial, the model thought to be the gold standard for scientific research. And of those 11 diets, only two— Weight Watchers and Jenny Craig— indicated that people who used the programs lost more weight after 12 months than people following their own diet.

Researchers conducted the study as a follow-up to a 2005 systematic review of commercial and proprietary weight loss programs, which was based on results from only three randomized controlled trials, and suggested that only Weight Watchers resulted in modest weight loss. The new study of 11 diets was based on 39 trials, all of which ran for at least 12 weeks.

“Losing weight and keeping it off is a top concern for most Americans,” lead study author Kimberly Gudzune, assistant medicine professor at Johns Hopkins University, told “I’m a physician myself, so I thought it was really important to give patients and their physicians guidance on programs to show which can really help them lose weight.”