A 24-month study compared a Mediterranean-style eating plan with a calorie-focused weight loss program.
Both groups lost and maintained weight, with returning participants losing about 10 pounds on average.
The Mediterranean-style group made bigger improvements in overall diet quality, including eating more healthy fats and fewer carbohydrates.
The Mediterranean diet has long been associated with an emphasis on foods such as vegetables, fruits, whole grains, nuts and healthy fats. But researchers at the University of North Carolina at Chapel Hill wanted to see what would happen if those principles were adapted to the foods and preferences of people living in the Southeast.
The resulting approach, called the Med-South Weight Loss Program, emphasizes foods including nuts, vegetable oils, whole grains, non-starchy vegetables and fruit. Researchers tested whether this eating pattern could help people lose weight while also improving the overall quality of their diets.
The findings, published in JAMA Network Open, suggest that focusing on the quality of the foods you eat may offer an additional benefit during a weight loss program — even when it doesn't necessarily lead to more weight loss.
How the study worked
The study included 360 adults with a body mass index of 30 or higher who were recruited from seven primary care practices in central North Carolina. Participants were randomly assigned to either the Med-South program or a control program that primarily focused on reducing calorie intake.
The Med-South program lasted 24 months and was divided into three phases. The first four months focused on improving diet quality. Months five through 12 shifted the focus toward weight loss while maintaining the eating pattern, followed by a final phase focused on maintaining weight loss.
Researchers assessed participants at four, 12, and 24 months, looking at measures including body weight, diet quality, and blood pressure. They also used food questionnaires and a device called the Veggie Meter to assess carotenoid levels in the skin, which can reflect fruit and vegetable intake.
What the results mean for you
The results weren't quite a case of one diet beating the other. After 24 months, there was no significant difference in weight loss between the two groups.
In the study's primary analysis, participants in the Mediterranean-style group lost an average of 3.40% of their body weight, compared with 3.51% in the control group. Among people who returned for follow-up visits, average weight loss was about 4.5 kilograms, or roughly 10 pounds, in both groups.
Where the Med-South approach stood out was diet quality. Participants reported greater improvements in measures of overall diet quality, along with higher intake of monounsaturated and polyunsaturated fats and lower carbohydrate intake.
“Incorporating a healthful dietary pattern into lifestyle weight loss programs should be a priority,” researcher Thomas Keyserling, M.D., MPH, said in a news release. “While similar weight loss can be achieved with calorie-restricted diets, there are added benefits to chronic disease prevention associated with a healthful dietary pattern.”
For consumers, that suggests a weight loss plan doesn't necessarily have to revolve around calories alone.
The researchers say more work is needed to understand exactly how those diet-quality improvements may affect long-term health.