However, Shai noted that even though the people on the low-carb diet were not given a calorie restriction, they ended up eating a similar number of calories as the people in the calorie-restricted groups, Shai said. Ultimately, all of the groups cut their calories by about 400 to 500 calories a day, she said. In other words, the study suggested that calories do matter for weight loss.
In the follow-up four years later, the researchers found that all of the participants had regained some of the weight. Over the entire six-year period, the average total weight loss was 6.8 lbs. (3.1 kg) for the Mediterranean-diet group and 3.7 lbs. (1.7 kg) for the low-carbohydrate group. The average weight loss of 1.3 lbs. (0.6 kg) for the low-fat group was not statistically significant, meaning that the finding could have been due to chance, the researchers wrote.
One reason the Mediterranean diet appeared to be the most effective for weight maintenance is that, simply put, in real life, a more “balanced” diet that offers many options may work best in the long term, Shai said. [Mediterranean Diet: Foods, Benefits & Risks]
Dr. George Bray, a professor emeritus at Pennington Biomedical Research Center at Louisiana State University and the founder of The Obesity Society, agreed.
“I’m a fan of using a high-quality, good-pattern diet with lower amounts of food, and one way of doing that is with portion control,” Bray said. Plenty of evidence suggests the Mediterranean diet is highly beneficial for people’s health and, combined with portion control, is a good strategy for weight loss, Bray told Live Science. The DASH diet, which was developed to lower blood pressure, also has shown weight loss benefits, he said. The DASH diet is a low-sodium diet that’s rich in fruits, vegetables, low-fat dairy, nuts, beans and seeds.
“As far as I can see, nothing else is of value,” Bray told Live Science. “It comes down to calories — pure and simple.” [Best Calorie Counter App]
Bray was one of the authors on another major weight loss study, called the Preventing Overweight Using Novel Dietary Strategies study, or the POUNDS Lost study.
In that study, two teams of researchers — one in Boston and one in Baton Rouge, Louisiana — carried out the randomized trial, which was — and still is — the largest clinical trial designed to compare the weight loss effects of different diets. (The study had more participants than the DIRECT study, although the study period for the POUNDS Lost study was shorter.)
The POUNDS Lost study began with more than 800 participants (400 in Boston, and 400 in Baton Rouge) who were randomly assigned to one of four diets: low-fat with average protein, low-fat with high protein, high-fat with average protein and high-fat with high protein. A total of 645 people completed the study.