Low-fat diets ineffective in achieving long-term weight loss, scientists say

A recent analysis of dietary practices of over 68,000 adults revealed that low-fat diets are ineffective in achieving long-term weight loss. Experts said that there is insufficient evidence to support recommendation of low-fat diets, as reducing fat intake will not naturally lead to weight loss.

After the subjects of the study took a year of low-fat diets, the dietary intervention has become either comparable to or less effective than other kinds of diets, such as higher-fat diets, Mediterranean diets and low-carbohydrate diets.

“There is no good evidence for recommending low-fat diets,” said Dr Deirdre Tobias from Harvard Medical School and lead author of the study in a report by Science Alert. “Behind current dietary advice to cut out the fat, which contains more than twice the calories per gramme of carbohydrates and protein, the thinking is that simply reducing fat intake will naturally lead to weight loss. But our robust evidence clearly suggests otherwise,” he added.

However, a low-fat diet is not the only dietary intervention that's ineffective for losing weight in the long term. The new study, published in The Lancet Diabetes & Endocrinology, shows that all types of diets are not particularly effective in helping people shed pounds.

With the types of diets involved in the study, the analysis shows that the average weight loss after a year was only 3.75 kilogrammes. Even the best-performing dietary intervention, the low-carb diet, has been found unable to maintain an impressive result after 12 months, the researchers said.

The findings come from the metaanalysis of 53 different studies involving 68,128 adults. The study focused on the effectiveness of low-fat diets compared with other types of diets.

The findings revealed that low-carb diet led to greater weight loss than low-fat diet. After a year, however, the gap between the two was small, with only 1.15 kilogrammes. Low-fat diets also remain the least effective among other kinds of higher-fat dietary interventions, and it also made a small difference with only 0.36 kilogramme lost, which was considered clinically meaningless.

“Although statistically significant, such a minuscule difference in weight loss is clinically meaningless,” said Kevin Hall from the U.S. National Institute of Diabetes and Digestive and Kidney Diseases in a commentary on the research. He added that the overall average weight loss in every kind of diet prescriptions in the study was “unimpressive.”

Hall said that the findings are clear that long-term diet adherence is difficult with any type of dietary intervention prescribed, including low-fat diets and low-carbohydrate diets. He noted that more studies are required to identify the factors affecting diet adherence in order to help maintain weight loss in the long term.

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