For decades, shifting opinions about the relative benefits of low-carbohydrate and low-fat diets have provided fodder for dietary guidelines, food marketers and diet gurus. According to the findings of a study published by the American Medical Association, the answer to questions about which is better is “both”—if consumption of processed foods is kept to a minimum.
For the study, researchers enrolled more than 600 overweight adults and randomly assigned them to either a “healthy low-fat” or “healthy low-carbohydrate” diet. Each group was instructed to limit intake of either fat or digestible carbohydrates to a specified daily total for eight weeks, and then to slowly increase this to a level they felt they could sustain for life.
Neither group was given restrictions regarding their intake of other macronutrients. But both were told to eat minimally processed food, prepared at home as much as possible, to maximize vegetable consumption and to limit intake of sugar, refined flour and trans-fat.
At the start of the study, and again at its sixth and twelfth month, researchers gave study participants glucose tolerance tests, to determine whether differences in insulin function affected outcomes from each diet. They also assessed participants for genetic factors that might affect their fat or carbohydrate metabolism.
After 12 months, they found that the mean weight loss in both groups was so similar that no statistical difference could be detected. In addition, they found no association between insulin response or genetics and the results obtained from both diet types, suggesting that it may be unnecessary to tailor diets to one body type or another.
The findings contradict conventional wisdom that losing weight is simply a matter of reducing calories. Dieters may not need to avoid food after all—just processed food products made with refined starches and added sugar.
Christopher D. Gardner, director of nutrition studies at the Stanford Prevention Research Center, led the research. “We really need to focus on that foundational diet, which is more vegetables, more whole foods, less added sugar and less refined grains,” he told the New York Times.
“This is the road map to reducing the obesity epidemic in the United States,” said cardiologist Dr. Mozaffarian, dean of the Friedman School of Nutrition Science and Policy at Tufts University of the findings. “It’s time for U.S. and other national policies to stop focusing on calories and calorie counting.”
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