The trial included 322 people, ages 40 to 65, all of whom were overweight and worked at the same research center. The participants were randomly assigned to different diets — a low-fat diet, a Mediterranean diet or a low-carb diet — for a two-year period. The researchers also conducted a follow-up four years after that, so the total study period was six years. The participants in the low-fat diet group and the Mediterranean-diet group were instructed to cut their calories, while those on the low-carb diet were given no calorie restrictions.
As in the WHI study, the participants received diet guidance in small group sessions. (One key difference between the two studies, however, was that in the DIRECT study, everyone was assigned to a group session.) In addition, because all of the participants worked at the same place, the researchers provided lunch each day. Each diet group was given a lunch that fit their diet,