We have more proof that no single diet reigns supreme. Slashing either carbs or fats can trim the waistline to the same degree, according to a major study from Stanford University School of Medicine in conjunction with the U.S. National Institutes of Health. The study was published in JAMA in February.
Researchers recruited 609 overweight men and women, who were then randomly divided into two diet groups—a low-carbohydrate group and a low-fat group—for 1 year. In the first 8 weeks of the study, participants were instructed to limit their daily intake of either carbs or fat to 20 grams. In the next phase, they were encouraged to gradually add back small amounts of high-quality carbs or fat (depending on their group) until they felt they’d found a sustainable balance.
Eventually, the low-fat group’s diet shifted to about 29% of calories from fat and about 48% from carbs, while the low-carb group’s diet moved to roughly 30% of calories from carbs and 45% from fat—numbers deemed sustainable over the long term.
Protein intake was matched between diet interventions. By study’s end, people in the two groups had lost similar amounts of weight, about 12 1/2 pounds. Baseline insulin secretion levels and specific gene patterns associated with carbohydrate and fat metabolism had no notable impact on people’s dieting success.
The take-home message? Regardless of diet, the keys to sustained weight loss are practicing portion control (which, in turn, better manages overall calorie intake); eating mostly unprocessed, nutrient-dense whole foods; and choosing a diet plan that one can stick to.