Dietary fat has always been targeted, said the study, for the reason that every gram (0.04 ounce) of it contains more than double the calories of a gram of carbohydrates or protein.
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The results were clear: Low-fat diets weren’t any more effective than high-fat diets when it came to losing weight and sustaining that loss over a long period of time.
In addition, higher fat diets that are low in carbohydrates were slightly but significantly more likely to lead to long-term weight loss compared to a low-fat approach.
“But our robust evidence clearly suggests otherwise”, said lead author Deirdre Tobias from Harvard Medical School, Boston, US.
However low-fat diets led to a greater weight loss only when compared to “usual diet” in which participants did not change their eating habits.
For decades, there has been debate over the merits of a low fat diet, which was endorsed as the best route to weight loss in the 1970s.
In the study, published today in the journal Lancet, the typical weight loss was about 7 pounds – an amount that researchers consider insignificant because most study participants were overweight or obese to begin with, and meant to lose many pounds. The research was supported by the American Diabetes Association and the U.S. National Institutes of Health.
Twenty of the trials included specifically enrolled patients with chronic diseases and 35 were designed specifically to compare weight loss interventions; 13 of the trials had no intended intervention for weight loss, and five were created to maintain a certain body weight.
The era of the low-fat diet may be nearing an end.
For successful weight loss, Diekman advises talking with a registered dietitian “who can design an eating plan for weight loss that meets your lifestyle”. BWH is also home to major landmark epidemiologic population studies, including the Nurses’ and Physicians’ Health Studies and the Women’s Health Initiative as well as the TIMI Study Group, one of the premier cardiovascular clinical trials groups.
“Energy balance calculations suggest that at the point of maximum weight loss, diet adherence has already substantially waned”, he wrote.
JON BUCKLEY: A calorie is a calorie so it doesn’t matter whether you’re getting that calorie from fat, from protein or from carbohydrate and you’ll still achieve the same weight loss over the longer term.
But doctors said any diet which reduced portion size and focussed on a healthy balanced range of fresh and unprocessed foods could form an effective route to weight loss.
“Much more research is needed to determine the factors that affect diet adherence and thereby help maintain weight loss over the long term”, writes Hall.
The researchers looked at studies comparing low-fat diets with other types of diets – or to no diet at all for at least a year.
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Keith Ayoob, RD, EdD, at the Albert Einstein College of Medicine in New York, added that he didn’t find the results surprising, since there are lots of ways to lose weight.
