A two-year primary care trial tested whether putting food quality at the center of weight management could change what participants ate and how well they maintained weight loss.
Paper: Weight Loss Intervention Promoting an Adapted Mediterranean-Style Dietary Pattern. Image Credit: Gecko Studio / Shutterstock
The DELISH randomized clinical trial found that an adapted Mediterranean-style dietary intervention produced modest weight loss comparable to that of a commercial weight-loss program while improving diet quality among adults with obesity. The findings are published in JAMA Network Open.
Background
Obesity, characterized by excessive fat accumulation in the body, has become a major public health challenge worldwide. More than 1 billion individuals worldwide are living with the condition, representing 1 in 8 adults. Obesity is a well-known risk factor for several chronic diseases, including cardiovascular disease and type 2 diabetes.
Poor lifestyle behaviors, such as an unhealthy diet and physical inactivity, are major determinants of obesity development and progression.
A substantial body of evidence suggests that diets rich in high-quality carbohydrates and fats are associated with lower risks of cardiovascular disease and several other chronic diseases, while Mediterranean-style diets have been shown in randomized trials to reduce cardiovascular events compared with low-fat diets.
The Mediterranean dietary pattern, which prioritizes high-quality fats, such as nuts, seeds, and vegetable oils, and carbohydrates, such as whole grains, fruits, and vegetables, has been associated with broad health benefits, although it remains relatively understudied in weight loss intervention trials in the United States.
Since this dietary pattern is based on traditional foods from countries around the Mediterranean Sea, people from different regional, cultural, and ethnic backgrounds may face challenges in applying Mediterranean-specific recommendations to their own lifestyles.
Given these challenges, researchers from the University of North Carolina at Chapel Hill, together with their collaborators, developed a Mediterranean-style dietary intervention tailored for populations in the southeastern United States.
To evaluate the weight-management efficacy of this dietary intervention, they conducted a randomized clinical trial, named Delicious Eating for Life in Southern Homes (DELISH) trial, on 360 primary care patients with obesity.
Trial Design
The participants were randomized to receive either the Mediterranean-style dietary intervention or a control intervention focusing on reducing energy intake. Both interventions were delivered over a 24-month period.
The Mediterranean-style intervention had three phases: phase 1 (1-4 months) focused on improving diet quality; phase 2 (5-12 months) focused on weight loss; and phase 3 (13-24 months) focused on weight loss maintenance.
The control intervention included access to the workshop and digital components of the WW program (now WeightWatchers), an established commercial weight-loss program. Both groups also received advice to promote regular, moderate-intensity physical activity.
Data on body weight, diet quality, and other physiological parameters were collected at baseline and at 4-month, 12-month, and 24-month follow-up visits.
Key findings
The assessment of participants’ body weight at the 24-month follow-up showed no significant difference in the percentage change in body weight between the Mediterranean-style group and the control group. The average reduction in body weight at the 24-month follow-up was approximately 5 kilograms in the Mediterranean-style group and 4 kilograms in the control group.
Participants in the Mediterranean-style group reported greater improvements in diet quality than control participants at all follow-up visits. The improvement was characterized by a greater proportion of energy from monounsaturated and polyunsaturated fats and a lower proportion of energy from carbohydrates. Diet-quality scores also improved more in the Mediterranean-style group than in the control group.
Significance
This randomized clinical trial found no meaningful difference in weight loss between a Mediterranean-style dietary intervention adapted for the southeastern United States population and an established commercial weight-loss intervention among primary care patients with obesity, most of whom had multiple chronic medical conditions.
However, the Mediterranean-style intervention produced significantly greater improvements in self-reported diet quality than the control intervention, as reflected in diet-quality scores and shifts toward a greater proportion of energy from unsaturated fats and a lower proportion from carbohydrates.
Failure to maintain achieved weight loss is a major disadvantage of intensive weight-loss interventions. In the current trial, among participants who returned for follow-up, those in the Mediterranean-style intervention group achieved about 5 kilograms of weight loss at the 12-month follow-up, which was sustained through the 24-month follow-up.
In the control group, returning participants achieved about 4.5 kilograms of weight loss at the 12-month follow-up, which was largely maintained at the 24-month follow-up. The sustained weight loss in the control group was notable because the researchers had expected greater attenuation after its larger initial weight loss.
Notably, the trial provides detailed insight into intervention-mediated changes in diet quality, which are rarely reported as outcomes in weight-loss trials. Among returning participants in the Mediterranean-style group, the improved dietary pattern was maintained through the 24-month follow-up. If this improved diet quality could be maintained over the long term, the authors note that, based on prior evidence, it would be expected to reduce obesity-related morbidity.
The Mediterranean-style intervention did not, however, show clear superiority across other measured health outcomes. Blood pressure reductions were similar between groups, changes in HbA1c were minimal overall, and changes in physical activity and depression scores did not significantly differ between groups.
Overall, the trial findings suggest that people with obesity who want to avoid or cannot afford weight-loss medications or surgery, or who want to achieve modest weight loss, may consider an intensive behavioral weight-loss intervention as a reasonable option, preferably one that focuses on diet quality.
However, one potential limitation of the trial is its reliance on self-reported diet quality, which may introduce recall and social desirability biases. Furthermore, the Mediterranean-style intervention was adapted for populations in the southeastern United States, which may restrict the generalizability of the findings to other US or international populations.
Only about 69% of participants attended the final measurement visit, although electronic health records provided 24-month weight data for approximately 94% of the sample.
The study also had limited power for subgroup comparisons, and the COVID-19 pandemic altered intervention delivery and may have affected participation and follow-up. In addition, the lack of a usual-care control group means that secular changes affecting body weight could not be fully accounted for.
