Low-fat diets are not better for weight loss

Low-fat diets are unlikely to result in greater weight loss than higher-fat diets that have the same amount of calories, a new study finds.

Researchers looked at the effectiveness of low-fat diets compared with other diets and not dieting at all, in a large analysis of previous studies. The scientists found no difference in people's average weight loss when comparing low-fat and higher-fat diets. Reducing fat only led to greater weight loss when compared to not following any type of diet.

In order to lose weight, it's essential to burn more calories than you take in. Reducing calorie intake by 500 to 1,000 calories per day could help a person lose 1 to 2 pounds (0.45 to 0.9 kilograms) per week, according to the Centers for Disease Control and Prevention (CDC).

Although cutting calories is key, the new results do not support reducing fat as an effective weight-loss strategy, said Dr. Deirdre Tobias, lead author of the study and an instructor at Brigham and Women's Hospital and Harvard Medical School in Boston. [7 Diet Tricks That Really Work]

"We don't eat calories per se — we eat foods," Tobias said. For weight-loss efforts, "the focus needs to shift away from specific nutrients — carbs and fats — to a discussion of healthy foods and eating patterns."

For the new analysis, researchers looked at 53 studies, involving more than 68,000 adults. The researchers compared average weight loss among reduced-fat diets, low-carbohydrate diets, higher-fat diets and no specific diet regimen. The investigators took into account the intensity of the diets; in some studies, participants were only given instructions about what to eat during the study, whereas others involved intensive programs including meetings with a dietician, counseling sessions, cooking lessons and the maintenance of food diaries.

Altogether, the findings suggest that the long-term effects of a low-fat diet depend enormously on the how intense the regimen was, the study said.

And while the findings do not suggest that low-fat diets are better than other dietary interventions on average, some people who want to lose weight may still need to cut some fat from their diets, Tobias said. People who want to lose weight should shift to healthy choices in ways that that are specific to them, she said.

The researchers said it is unclear exactly why higher-fat diets were slightly more effective for long-term weight loss when compared to low-fat diets. In some cases, people on higher-fat diets may have had a greater reduction in their calorie intake; however, this wasn't true in all the trials, Tobias said.

And it's important to remember that even if low-fat diets aren't the best strategy for long-term weight loss, certain types of fats — including trans fats and saturated fats — remain unhealthy.

"Having a diet that includes healthy foods that one prefers is likely to increase long-term adherence [to a weight-loss regimen], and therefore increase long-term weight loss and weight maintenance," Tobias told Live Science.

A low-fat diet can still be healthy. "It's possible that personal preferences would lead someone to adopt a diet lower in total fat, and this can be relatively healthy if it's low in refined grains [and] processed meats, and higher in fruits, vegetables and whole grains," she said.

Dr. Kevin Hall of the National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland, who was not involved in the study, noted that the results should be seen more from the standpoint of how well people respond to being on a diet.

"What we know is that people are very poor at following a diet over the long term, as well as going back to old habits," he said. "What this study is highlighting is that this is, indeed, a problem, and what we want to understand is why some people do well on certain diets and others don't."

The study was published Oct. 29 in The Lancet Diabetes & Endocrinology journal.

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