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Low-fat diet not most effective in long-term weight loss

Researchers conduct a systematic review of randomized clinical trials comparing the long-term effectiveness of low-fat and higher-fat dietary interventions on weight loss

Brigham and Women's Hospital

Researchers conduct a systematic review of randomized clinical trials comparing the long-term effectiveness of low-fat and higher-fat dietary interventions on weight loss

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. Researchers from Brigham and Women's Hospital (BWH) and the Harvard T.H. Chan School of Public Health (HSPH) conducted a comprehensive review of the data generated from randomized clinical trials that explored the efficacy of a low-fat diet and 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.

These results are published in The Lancet Diabetes & Endocrinology on October 30, 2015.

"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 Deirdre Tobias, ScD, a researcher in the Division of Preventive Medicine at BWH. "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. 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."

In this meta analysis of randomized clinical trials comparing the long term effect (longer than one year) of low-fat and higher-fat dietary interventions, researchers analyzed data from 53 studies with a total of 68,128 participants that were designed to measure the difference in weight change between two groups that had a dietary intervention (low-fat or other diet). Trials that included dietary supplements or meal replacement drinks were excluded from the analysis. On average, trial participants across all intervention groups only managed to lose and keep off six pounds at one year or longer. 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. Researchers also report that low-fat diets led to a greater weight loss only when compared to 'usual diet' in which participants did not change their eating habits.

"Current evidence indicates that clinically meaningful weight loss can be achieved with a variety of dietary approaches," said Frank Hu, senior author of the paper and Professor of Nutrition and Epidemiology at Harvard T.H. Chan School of Public Health. "The key is to improve long-term compliance and cardiometabolic health. Therefore, weight loss diets should be tailored to cultural and food preferences and health conditions of the individual and should also consider long-term health consequences of the diets."


This research was funded by the National Institutes of Health (DK082730, HL34594, HL60712, CA176726, DK58845, DK46200, DK103720, and CA155626) and the American Diabetes Association.

Brigham and Women's Hospital

Brigham and Women's Hospital (BWH) is a 793-bed nonprofit teaching affiliate of Harvard Medical School and a founding member of Partners HealthCare. BWH has more than 4.2 million annual patient visits, nearly 46,000 inpatient stays and employs nearly 16,000 people. The Brigham's medical preeminence dates back to 1832, and today that rich history in clinical care is coupled with its national leadership in patient care, quality improvement and patient safety initiatives, and its dedication to research, innovation, community engagement and educating and training the next generation of health care professionals. Through investigation and discovery conducted at its Brigham Research Institute (BRI), BWH is an international leader in basic, clinical and translational research on human diseases, more than 1,000 physician-investigators and renowned biomedical scientists and faculty supported by nearly $600 million in funding. For the last 25 years, BWH ranked second in research funding from the National Institutes of Health (NIH) among independent hospitals. BWH continually pushes the boundaries of medicine, including building on its legacy in transplantation by performing a partial face transplant in 2009 and the nation's first full face transplant in 2011. BWH is also home to major landmark epidemiologic population studies, including the Nurses' and Physicians' Health Studies and the Women's Health Initiative as well as the TIMI Study Group, one of the premier cardiovascular clinical trials groups. For more information, resources and to follow us on social media, please visit BWH's online newsroom.

Harvard T.H. Chan School of Public Health

Harvard T.H. Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and produce powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, educators, and students, we work together to take innovative ideas from the laboratory to people's lives--not only making scientific breakthroughs, but also working to change individual behaviors, public policies, and health care practices. Each year, more than 400 faculty members at Harvard Chan teach 1,000-plus full-time students from around the world and train thousands more through online and executive education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is recognized as America's oldest professional training program in public health.

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