The new research was published in JAMA and led by Christopher D. Gardner, the director of nutrition studies at the Stanford Prevention Research Center. It was a large and expensive trial, carried out on more than 600 people with $8 million in funding from the National Institutes of Health, the Nutrition Science Initiative and other groups.
Dr. Gardner and his colleagues designed the study to compare how overweight and obese people would fare on low-carbohydrate and low-fat diets. But they also wanted to test the hypothesis suggested by previous studies that some people are predisposed to do better on one diet over the other depending on their genetics and their ability to metabolize carbs and fat. A growing number of services have capitalized on this idea by offering people personalized nutrition advice tailored to their genotypes.
The researchers recruited adults from the Bay Area and split them into two diet groups, which were called healthy low carb and healthy low fat. Members of both groups attended classes with dietitians where they were trained to eat nutrient-dense, minimally processed whole foods, cooked at home whenever possible.