Unlike in the WHI study, the low-fat diet in the DIRECT study didn’t result in the most weight loss. Rather, weight loss was the highest in the low-carb group — the participants in this group lost an average of 12.1 lbs. (5.5 kg) after two years. The participants in the Mediterranean-diet group lost, on average, 10.1 lbs. (4.6 kg), and the participants in the low-fat group lost, on average, 7.3 lbs. (3.3 kg) after two years.
Additionally, there was a difference in which diets were the most effective for each sex. The women in the study who were on the Mediterranean diet lost more weight than the women on the low-fat diet. In comparison, the men on the low-carb diet lost more weight than the men on the low-fat diet, the researchers found. (However, only 45 women completed the study, compared with 277 men.) In other words, both women and men lost more weight on a diet other than the low-fat diet.
The DIRECT study showed that one diet doesn’t fit all, said Iris Shai, a professor of nutrition and epidemiology at Ben-Gurion University of the Negev in Israel and the lead author of the study. In other words, the researchers learned that there are some alternatives to a low-fat diet that also work for weight loss, Shai told Live Science. These alternatives (the low-carb diet and the Mediterranean diet) also have more health advantages in the long run, such as improved cholesterol and blood sugar levels, respectively.