Researchers at Brigham and Women’s Hospital and the Harvard T.H. Chan School of Public Health reviewed data from clinical trials to look at how effective low-fat diets were.
The study, Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults: a systematic review and meta-analysis, found that low-fat interventions were no more effective than higher-fat diets at maintaining weight loss for longer than a year.
“These findings suggest that the long-term effect of low-fat diet intervention on body weight depends on the intensity of the intervention in the comparison group,” said the study, which was printed in The Lancet Diabetes & Endocrinology.
“When compared with dietary interventions of similar intensity, evidence from [randomized controlled trials] does not support low-fat diets over other dietary interventions for long-term weight loss.”
What the analysis found
The researchers looked at a systematic review and random effects meta-analysis of randomized controlled trials that compared long-term effects of low-fat and higher-fat diets.
In all, 53 studies with nearly 70,000 participants were reviewed.
On average, trial participants in either group lost about six pounds over one year or longer.
Those in low-carbohydrate weight-loss diets ended up keeping off an additional two-and-a-half pounds after a follow up at least one year later.
When it came to low-fat diets, researchers said it only offered a greater potential for weight loss than the “usual diet” of trial participants. This means a low-fat diet is only slightly better than keeping the same diet as usual over time.
Cut the low-fat
While it has been common to see low-fat dairy products pushed out for many years, this study adds another brick in the wall of information that fat from dairy products may not be bad for health after all.
Deirdre Tobias, a researcher with the Division of Preventive Medicine at BWH, said despite the belief that cutting fat from a diet helps fat loss, the existing scientific evidence does not back that up in the least.
“In fact, we did not find evidence that is particularly supportive of any specific proportion of calories from fat for meaningful long-term weight loss,” she said.
“We need to look beyond the ratios of calories from fat, carbs, and protein to a discussion of healthy eating patterns, whole foods, and portion sizes. Finding new ways to improve diet adherence for the long-term and preventing weight gain in the first place are important strategies for maintaining a healthy weight.”
It remains to be seen how the dairy industry will respond, but there have already been moves to create products with a higher fat content, including one from Peak Yogurt which boasts triple the fat of regular yogurt.
Source: Lancet Diabetes Endocrinol http://dx.doi.org/10.1016/S2213-8587(15)00367-8
Title: Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults: a systematic review and meta-analysis
Authors: D. Tobias, M. Chen, J. E Manson, D. Ludwig, W. Willett, F. Hu