Published in the Journal of Health Psychology, the research found that almost three in five (57 per cent) people who signed up to commercial weight loss programs lost less than five per cent of their initial body weight.
Lead researcher Samantha McEvedy said what programs offered in terms of weight loss did not match outcomes in most cases.
“For someone who weighs 100 kilograms, five percent weight loss equates to losing five kilos, an amount which would be enough to reduce health risks for someone who is overweight but which is much lower than the substantial weight losses these programs typically describe in their advertising and testimonials,” Ms McEvedy said.
“Our research demonstrates that, although commercial weight loss programs may help people to lose weight in the short term, the amount of weight lost is often not enough to be clinically meaningful.”
Ms McEvedy said the research found that dieters who remained in a commercial weight loss program, as opposed to dropping out before study completion, were more likely to achieve modest but meaningful weight loss. However, the dropout rate is typically quite high.
“High rates of attrition from commercial weight loss programs suggest that many dieters find the dietary changes required by these programs unsustainable.”
“Those who complete the program, sticking with it for the prescribed study period, were more successful. But even among this group, we found that around two in five (37 per cent) lost less than five per cent of their initial body weight.”
The research involved a systematic review and meta-analysis of 25 published studies on commercial weight loss programs, including meal replacement, calorie-counting or pre-packaged meal programs.
“In light of the popularity of these programs, it is crucial that we evaluate their effectiveness and that consumers be well-informed and have realistic expectations upon which to base any dieting decisions,” Ms McEvedy said.
“Commercial programs which educate people about how to make consistently healthy food choices, control portion sizes and encourage regular physical activity may still have a role to play in the fight against Australia’s rising rates of obesity.”
Media contact Anastasia Salamastrakis 0428 195 464