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Low Fat Diets Do Not Lead to Greater Weight-Loss Compared To Higher Fat Diets


The success of low-fat diets and weight-loss overall has been bickered about for decades now and hundreds of randomized clinical trials directed at figuring out this problem have been done with varied results.

Researchers from Brigham and Women’s Hospital (BWH) and the Harvard T.H. Chan School of Public Health (HSPH) managed an extensive large meta data analysis from randomized clinical trials that researched the effectiveness of a low-fat diet. They established that low-fat diets weren’t more rewarding than higher-fat diets of similar intensity (e.g. low-carbohydrate or Mediterranean diets) in achieving and maintaining weight loss for periods that were longer than a year in non-pregnant adults up to the end of July 2014.

Researchers compared the long term reaction, year longer or more, of low-fat and higher-fat dietary interventions and they studied the data obtained from 53 different studies involving a total of 68,128 partakers that were formed to measure the difference in weight variation between two groups that had a dietary intervention (low-fat or other diet). Trials that included meal replacement drinks and dietary supplements were removed from this study. They considered the intensity of the diets which ranked from just brochures or instructions at the beginning of the program to more intensive multivariate programs that included meetings with dieticians, food diaries, cooking lessons and counseling sessions.

Results showed that on average, trial participants across all intervention groups only managed to lose and keep off 6 pounds (2.7 kg) for a period that was at least 1 year long. Comparing participants from low-fat diets to participants in a low-carbohydrate weight loss program showed that they were “only” about 2.5 pounds (1.13 kg) lighter after a period of at least one year. Researchers also concluded that low-fat diets led to a higher weight loss only when compared to normal diets without a real plan in which partakers did not change their eating patterns.

Lead researcher, Dr Deirdre Tobias, from BWH and HSPH commented:

»There is no good evidence for recommending low-fat diets, behind current dietary advice to cut out the fat, which contains more than twice the calories per gram 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.

The science does not support low-fat diets as the optimal long-term weight loss strategy. 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–the proportion of calories that come from fat, carbohydrate, and protein. Long-term adherence is critical for the success of any dietary intervention, and one should also take into account other long-term health effects of their dietary choices.«

Obesity is one of the most serious global public health challenges, obesity has more than doubled from 1980. In 2014, more than 1.9 billion adults that are 18 years or older, were overweight and of these over 600 million were obese.

This study has been published in the journal The Lancet Diabetes & Endocrinology in a paper titled: “Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults: a systematic review and meta-analysis”.

About the author

Warren Simons