Mediterranean-Style and WW Programs Yield Similar Weight Loss

The DELISH randomized clinical trial found no material difference in 24-month weight loss between an adapted Mediterranean-style behavioral program and a commercial program focused on energy restriction, although diet-quality scores favored the Mediterranean-style intervention among participants who returned for follow-up. The findings were published in JAMA Network Open.

The trial enrolled 360 adults aged 18 to 75 years with a body mass index of 30 or higher from 7 primary care practices in central North Carolina. Participants were randomized to the Med-South program (n=182) or a control program providing WW workshop and digital components (n=178). The Mediterranean-style intervention progressed from diet-quality counseling to weight loss and maintenance; both programs encouraged moderate-intensity physical activity.

In the intention-to-treat analysis with imputation for missing data, adjusted mean body-weight change at 24 months was −3.40% with the Mediterranean-style intervention and −3.51% with the control program, a difference of −0.11 percentage points (P=.90). The 24-month visit was completed by 64.8% and 72.5% of participants, respectively, although weight data were available for 94% of the sample through visit or electronic health record measurements.

Among participants who returned for follow-up, 24-month scores favored the Mediterranean-style group on the Alternative Healthy Eating Index-2010 (difference, 3.62 points; P = .005), DASH score (difference, 1.91 points; P < .001), and alternate Mediterranean diet index (difference, 1.15 points; P < .001). One likely intervention-related adverse event occurred: near syncope in a control-group participant receiving hypertension medication after substantial weight loss.

Limitations included self-reported dietary data, reduced in-person counseling during the COVID-19 pandemic, limited power for subgroup comparisons, regional tailoring of the Mediterranean-style program, and no usual-care group. Investigators concluded that both programs produced similar weight loss, while the Mediterranean-style approach yielded greater sustained improvements in reported diet quality among follow-up participants.

Source: Keyserling TC, Wu Q, Ammerman AS, et al. Weight loss intervention promoting an adapted Mediterranean-style dietary pattern: the DELISH randomized clinical trial. JAMA Netw Open. 2026;9(8):e2629006. doi:10.1001/jamanetworkopen.2026.29006