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Nov 19, 2015

Low-Fat Diets Not the Best Weight Loss Solution

A review of more than 50 clinical trials comparing low- versus higher-fat diets shows no significant difference in weight loss results.

With more than one-third of U.S. adults obese, identifying the best possible strategy for weight loss is desperately needed. However, studies have produced varying results, and it’s unclear which diet is best for long-term weight loss.

To learn more, researchers from Brigham and Women’s Hospital did a systematic review of all clinical trials comparing low-fat diets to other diets or no diets at all. Published in The Lancet Diabetes and Endocrinology, this review compared low-fat diets with higher-fat eating plans like the Mediterranean diet and low-carb diets. Both diets are higher in fat and have become a popular alternative to traditional low-fat diets like Weight Watchers in recent years.

A total of 53 studies involving more than 68,000 adults were included in the recent analysis. Overall, there was no significant difference in weight loss when comparing low- and higher-fat diets. In fact, researchers found that low-carb diets led to greater weight loss than low-fat diets, although differences in weight change were small.

However, studies consistently found that low-fat diets were more effective than no diet at all. When weight loss was not the primary goal of the diet, participants following a low-fat diet lost similar amounts of weight compared to other diets.

Based on findings, researchers argue there is no good evidence to recommend low-fat diets over other diets. As lead author Dr. Deirdre Tobias from Brigham and Women’s Hospital explains, “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.” Therefore, contrary to popular beliefs, cutting out fat may not be the best strategy for long-term weight loss.

However, it’s important to note that this study does not suggest that the low-fat diet is ineffective for weight loss. By and large, clinical trials have found that a low-fat diet helps people lose weight when compared to their usual diet. Many Americans have succeeded in losing and maintaining weight with low-fat diets like Weight Watchers.

The key, as authors explain, is finding a diet that individuals can maintain over time. According to Dr. Tobias, “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.” For example, choosing “good” fats and eating plenty of fruits and veggies is known to promote good health and help prevent heart disease. A well-balanced diet should not only help individuals achieve a healthy weight but also promote good overall health.

Authors also encourage future research on the issue. “To effectively address the obesity epidemic, we will need more research to identify better approaches for long-term weight loss and weight maintenance,” says Dr. Tobias. Out of all the diets currently available, it’s yet to be determined which diet is best for losing and keeping weight off.

Questions for You to Consider

  • What is a heart-healthy diet?

  • A heart-healthy diet is full of fruits, vegetables, beans and whole grains and includes low-fat dairy, fish and nuts as part of a balanced diet. It’s important to limit intake of added sugars, salt (sodium) and bad fats (saturated and trans fats).

  • What is the Mediterranean diet?
  • The Mediterranean diet is a way of eating rather than a formal diet plan. It features foods eaten in Greece, Spain, southern Italy and France, and other countries that border the Mediterranean Sea.

    The Mediterranean diet emphasizes eating foods like fish, fruits, vegetables, beans, high-fiber breads and whole grains, and olive oil. Meat, cheese, and sweets are very limited. The recommended foods are rich with monounsaturated fats, fiber, and omega-3 fatty acids.

    The Mediterranean diet is like other heart-healthy diets in that it recommends eating plenty of fruits, vegetables, and high-fiber grains. But in the Mediterranean diet, an average of 35-to-40% of calories can come from fat. Most other heart-healthy guidelines recommend getting less than 35% of your calories from fat. The fats allowed in the Mediterranean diet are mainly from unsaturated oils, such as fish oils, olive oil, and certain nut or seed oils (such as canola, soybean, or flaxseed oil). These types of oils may have a protective effect on the heart.  For more information, read this overview of the Mediterranean diet.

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