New Review Says Low Fat Diets Not More Effective Than Other Plans

It seems like an endless debate: What's the most effective way to lose excess weight?

In recent years, at least some of the debate has come down to the question: Is it low fat diets or low carb diets?

To answer at least part of that question, researchers at Brigham and Women's Hospital and the School of Public Health at Harvard have reviewed 53 recent studies on the topic. They say that review makes it clear that low fat diets are not any more effective than other weight loss plans.

Epidemiologist Deirdre Tobias, with the Division of Preventive Medicine at Brigham and Women's, joined Morning Edition's Bob Oakes to discuss the review.

When looking at sustaining weight loss for at least a year, are low fat diets any less effective than other diets? 

Overall, we found that it seemed across all diets that none were particularly successful. Low fat were certainly no more effective than higher fat diets. We did find that higher fat, low carbohydrate diets were slightly better than low fat. But overall, it seemed that focusing on a percent of calories from fat, whether it's higher or lower just wasn't an effective strategy for long-term weight loss.

Are you surprised that none of the diets seem to work? 

We were surprised and not surprised at the same time. We've seen a tremendous focus on weight loss and dieting products — stick to this diet plan or that diet plan — over the last several decades. But in the end, obesity and overweight have only gone up. So clearly something that we're doing is not right.

What's the best way to lose weight? 

This suggests that the best way to lose weight is probably not to focus on total fat, so our emphasis really should probably shift to healthy eating patterns and talking about foods rather than nutrients, because foods are what we eat at the end of the day. And we know foods that are good for us — fruits, vegetables, whole grains, limiting our intake of red and processed meat and refined grains and sugar. ... If we focus on foods and patterns, then these other nutrients that we think are potentially harmful for us like saturated fat, those will all fall into place. We'll end up having an overall healthy balanced diet for a number of reasons including weight loss.

Should we be counting calories? 

If we're serious about losing a significant amount of weight, of course we need to focus on calories. I don't know if that means we have to count every single one, but you know, eating extremely large portions, which probably got us there in the first place, is not going to be an optimal strategy to take the weight off.

Are there still health benefits to eating foods that are low in fat?

Certain foods yes. We know that things like dairy and meat products that are high in saturated fat in particular, these are fats that we do want to avoid. These are the bad fats, including trans fat, that we know for a number of reasons, such as cardiometabolic health or heart health, that we need to reduce in our diet. But this is a separate topic from weight loss.

If we say total fat, and villainize all fat, then that leads the public to swap out potentially good fats from things like nuts and olive oil and other healthy cooking oils for refined grains and sugars that are technically, potentially fat free even but certainly no more healthy for us.