A Mediterranean-style eating plan may be just as effective for long-term weight loss as a commercial weight-management programme while producing stronger improvements in overall diet quality, according to a newly published randomized clinical trial.
The DELISH trial, published in JAMA Network Open on August 20, 2026, followed 360 adults and compared an adapted Mediterranean-style weight-loss programme with the commercial WW (WeightWatchers) programme over 24 months. Researchers found no significant difference in weight loss between the two approaches—but important differences emerged in what participants were eating.
Both Approaches Produced Similar Weight Loss
Participants were randomly assigned to either the Med-South Weight Loss Program, an adapted Mediterranean-style intervention, or the commercial weight-management programme.
At 24 months, the adjusted average weight change was −3.40% in the Mediterranean group and −3.51% in the comparison group. The difference was not statistically significant.
Among participants who returned for follow-up, both groups achieved approximately 4% weight loss after two years.
That suggests a Mediterranean-style approach doesn’t necessarily produce greater weight loss—but it may achieve comparable results while changing diet quality in potentially meaningful ways.
Mediterranean Group Improved Diet Quality
This was where the Mediterranean intervention stood out.
Participants following the Mediterranean-style programme showed significantly larger improvements across several measures of diet quality. At 24 months, their Alternative Healthy Eating Index, DASH and Mediterranean-diet scores were all significantly higher than those of the comparison group.
The Mediterranean intervention encouraged a dietary pattern emphasizing foods such as vegetables, fruits, whole grains, legumes, nuts, fish and healthier unsaturated fats, rather than focusing exclusively on calorie reduction.
Healthy Eating Changes Lasted Two Years
Another encouraging finding was the durability of the dietary changes.
The Mediterranean intervention began with a four-month phase focused specifically on improving food quality. Participants subsequently reported maintaining much of that healthier dietary pattern through the 24-month follow-up.
That matters because losing weight is only one part of weight management. Maintaining both the weight change and a nutritionally balanced eating pattern over the long term can be considerably harder.
Weight Loss Isn’t the Only Goal
The findings reinforce a broader change taking place in nutrition and obesity research: the quality of food consumed may deserve attention alongside the number of kilograms lost.
Two diets can produce similar changes on the scale while providing very different amounts of fiber, healthy fats, minimally processed foods and nutrient-rich plant foods.
The researchers noted that Mediterranean-style dietary patterns have previously been associated with lower chronic-disease risk, although this particular trial was not designed to prove that its diet-quality improvements would translate directly into fewer cardiovascular events or longer life.
Is the Mediterranean Diet Better for Weight Loss?
Not necessarily.
The trial found no meaningful advantage in total weight loss compared with the commercial programme. It also had limitations, including declining follow-up participation over the two-year period, and its Mediterranean intervention was adapted specifically for populations in the southeastern United States.
Its most important finding is therefore not that one diet “beats” another.
Instead, the research suggests that people may be able to achieve similar long-term weight-loss results while simultaneously shifting toward a higher-quality dietary pattern.
For sustainable weight management, that could be an important distinction: success isn’t only about eating less—it may also be about learning to eat better in a way you can maintain for years.
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