Study: Do Low-Fat Diets Work for Weight Loss?

A Brigham and Women's and Harvard study says cutting fat may not be the way to drop pounds.

With a new food tied to health risks seemingly every day—this week’s processed meats news comes to mind—it may seem like an all-lettuce diet is just about our only remaining option. But a new study from Brigham and Women’s Hospital (BWH) and the Harvard School of Public Health (HSPH) says there may be one less thing you need to worry about: fat content.

The joint study sought to tackle a long-controversial question: Do low-fat diets work for weight loss? Past trials have proved inconclusive, but the new research suggests that, in the long-term, low-fat diets are often no better than any other methodology.

After completing an extensive meta-analysis of 53 studies that looked at long-term weight loss for people on low-fat versus higher-fat diets, the researchers found that respondents adhering to low-fat diets had roughly the same results as people following other eating plans. Low-carbohydrate dieters, on the other hand, were an average of 2.5 pounds lighter than low-fat eaters after a year or longer. The only time low-fat diets led to better weight loss was when compared with people who had not adapted their eating habits to be more healthful at all.

Deirdre Tobias, a preventive medicine researcher at BWH, said in a statement that the results suggest that fat content is not the most important thing to consider when choosing foods:

“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.”

It’s worth noting, however, that high-fat diets may be harmful to health in ways other than weight gain. Another recent study from HSPH, for example, found that cutting down on saturated fat may help individuals avoid coronary heart disease.