This study collates existing evidence regarding weight loss among overweight but otherwise healthy adults who use commercial weight-loss programs. Systematic search of 3 databases identified 11 randomized controlled trials and 14 observational studies of commercial meal-replacement, calorie-counting, or pre-packaged meal programs which met inclusion criteria. In meta-analysis using intention-to-treat data, 57 percent of individuals who commenced a commercial weight program lost less than 5 percent of their initial body weight. One in two (49%) studies reported attrition ≥30 percent. A second meta-analysis found that 37 percent of program completers lost less than 5 percent of initial body weight. We conclude that commercial weight-loss programs frequently fail to produce modest but clinically meaningful weight loss with high rates of attrition suggesting that many consumers find dietary changes required by these programs unsustainable.
Samantha M McEvedy, Gillian Sullivan-Mort, Siân A McLean, Michaela C Pascoe, & Susan J Paxton. (2017). Ineffectiveness of commercial weight-loss programs for achieving modest but meaningful weight loss: Systematic review and meta-analysis. Journal of Health Psychology.