The systematic review, published in The Lancet Diabetes & Endocrinology, pooled data from 53 randomised trials comparing the effectiveness of low-fat diets to other diets for long-term weight loss of least one year.
Led byDr Deirdre Tobias from Brigham and Women's Hospital and Harvard Medical School, the research team found that low-fat interventions were no more successful than higher-fat interventions in achieving and maintaining weight loss for periods longer than one year.
"Despite the pervasive dogma that one needs to cut fat from their diet in order to lose weight, the existing scientific evidence does not support low-fat diets over other dietary interventions for long-term weight loss," said Tobias.
"The thinking is that simply reducing fat intake will naturally lead to weight loss. But our robust evidence clearly suggests otherwise,” she said.
The Harvard-based team noted that the effectiveness of low-fat diet on weight-loss has been debated for decades, and hundreds of randomized clinical trials aimed at evaluating this issue have been conducted – with mixed results.
The new systematic review of this evidence involved a meta-analysis of 53 randomized clinical trials comparing the long term effect of low-fat and other higher-fat dietary diets – pooling data from 68,128 participants.
The team noted that on average, trial participants across all dietary intervention groups only managed to lose, and keep off, six pounds at one year or longer.
Analysis showed no significant difference in the average weight loss between reduced-fat diets and other diets.
Compared with low-fat diets, participants in low-carbohydrate weight loss interventions were about two and a half pounds lighter after follow-up of at least one year, said the team – who noted that low-fat diets only led to a greater weight loss when compared to 'usual diet' in which participants did not change their eating habits.
"The science does not support low-fat diets as the optimal long-term weight loss strategy,” said Tobias. “To effectively address the obesity epidemic, we will need more research to identify better approaches for long-term weight loss and weight maintenance, including the need to look beyond differences in macronutrient composition.”