Two-Year Trial Finds Mediterranean-Style Diet Matches Weight Watchers for Weight Loss While Improving Diet Quality
核心洞察
The DELISH randomized clinical trial found no significant difference in weight loss between an adapted Mediterranean-style diet and a commercial weight-loss program among 360 primary care patients with obesity (搜索).
Both groups achieved modest, sustained weight loss of roughly 4–5 kilograms over 24 months, with the Mediterranean-style group showing significantly greater improvements in diet quality.
The Mediterranean-style intervention shifted participants toward more unsaturated fats and fewer carbohydrates, a pattern the authors suggest could reduce obesity (搜索)-related morbidity if maintained long term.
A two-year randomized clinical trial conducted in primary care settings found that an adapted Mediterranean-style dietary intervention produced weight loss comparable to an established commercial weight-loss program, while delivering significantly greater improvements in diet quality among adults with obesity (搜索). The findings, published in JAMA Network Open, challenge the assumption that total weight loss is the only outcome that matters in weight management.
The trial, named Delicious Eating for Life in Southern Homes (DELISH), was led by researchers from the University of North Carolina at Chapel Hill and their collaborators. It enrolled 360 primary care patients with obesity (搜索), most of whom had multiple chronic medical conditions. Participants were randomized to receive either a Mediterranean-style dietary intervention tailored for populations in the southeastern United States or a control intervention focused on reducing energy intake.
Trial Design and Interventions
Both interventions were delivered over a 24-month period. The Mediterranean-style intervention was structured in three phases: phase 1 (months 1–4) focused on improving diet quality; phase 2 (months 5–12) focused on weight loss; and phase 3 (months 13–24) focused on weight loss maintenance. Participants received in-person and telephone counseling from dietitians throughout the program.
The control intervention included access to the workshop and digital components of the WW program (now WeightWatchers (搜索)), 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.
Comparable Weight Loss, Divergent Diet Quality
Assessment of body weight at the 24-month follow-up showed no significant difference in the percentage change in body weight between the two groups. The average reduction in body weight was approximately 5 kilograms in the Mediterranean-style group and 4 kilograms in the control group.
Among participants who returned for follow-up, those in the Mediterranean-style 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 12 months, which was largely maintained at 24 months. The sustained weight loss in the control group was notable because the researchers had expected greater attenuation after its larger initial weight loss.
Where the interventions diverged was diet quality. Participants in the Mediterranean-style group reported greater improvements in diet quality than control participants at all follow-up visits. This 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.
Clinical Significance and Limitations
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. The authors note that, based on prior evidence, if this improved diet quality could be maintained over the long term, it would be expected to reduce obesity (搜索)-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.
The authors suggest that people with obesity (搜索) 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. They also wrote that "it is important to further study the impact of a lifestyle program that focuses on diet quality as a co-intervention with effective weight loss medication," noting that such co-interventions might improve outcomes during treatment and reduce weight regain when medications are discontinued.
Several limitations warrant consideration. The trial relied on self-reported diet quality, which may introduce recall and social desirability biases. The Mediterranean-style intervention was adapted for populations in the southeastern United States, which may restrict generalizability 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.