Cutting Fat Isn't the Best Way to Lose Weight

When researchers tally all the studies, low-fat diets don't work any better than other ways to cut calories.

Photographer: Getty Images

I know what you're thinking. Another diet headline that will whiplash people trying to lose weight. The debate over the best way to shed pounds never ends. A new study isn't going to change that.

Deirdre Tobias hopes hers will. A researcher in the division of preventive medicine at Brigham and Women's Hospital in Boston, she co-authored a new analysis that finds reducing fat isn't any more effective for losing weight than other diets. The paper was just published on Thursday in the journal Lancet Diabetes & Endocrinology.

While fat-cutters lost some weight, compared with people who didn't diet at all, they lost less than carb-cutters in trials that lasted at least one year. No approach was a magic bullet, though. All the dieters in the studies Tobias analyzed lost, on average, just six pounds in a year. "That’s not very clinically meaningful," Tobias said. Such modest weight improvements won't dent the obesity epidemic that affects 35 percent of Americans1.

The conclusion is based on a meta-analysis—an aggregation of the results of many disparate studies—of long-term diet interventions that included data from more than 68,000 adults.

Tobias's take-away is that diets defined by meeting calorie thresholds for carbs, fat, and protein should be replaced by "guidelines built around whole foods and overall healthy eating patterns." 

"I’m hoping that the days of counting the percent balance of fat and carbs are nearing an end," she said. "There just clearly isn’t evidence to support it as relevant in weight loss."

Dietary guidelines (PDF) from the Department of Agriculture have long suggested capping fat intake, currently at 20 percent to 35 percent of total calories. Revised recommendations due this year are expected to focus less on specific proportions of carbs and fat and more on increasing nutritious foods overall.

The finding doesn't offer a carte blanche to switch to a bacon cheeseburger diet. Unhealthy saturated fats (mostly from meat and dairy) and trans fats (in margarine and other processed foods) remain unhealthy. But people shouldn't feel the need to arbitrarily limit their total intake of fats, especially from more nutritious sources such as fish, nuts, and vegetable oils.

What's important is finding ways to incorporate better foods into eating habits, not fad diets, said Kristin Kirkpatrick, manager of nutrition services at the Cleveland Clinic’s wellness institute. 

"Most people can’t stay on Atkins long-term, and most people can’t stay on an excessively low-fat diet for the long term either," she said. "For me and a lot of my friends who are dietitians, you need to adopt a diet where you’re not thinking of these things so intensely all day."

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  1. 1 An additional third are overweight but not obese.