Single-Component Versus Multicomponent Dietary Goals for the Metabolic Syndrome

Design: randomized controlled trial; Participants: 240 adults with metabolic syndrome, BMI 30-40 kg/m2, aged 21-70; Worcester, Massachusetts; non-smokers for ≥30 days; mean age 52, mean BMI 35, 72% female, 86% college educated; outcome assessors blinded; trial registration NCT00911885.

High fiber diet: aim for ≥30 g/day of dietary fiber; no caloric goals; delivered via two individual sessions and twelve group sessions over 12 months; focus on fiber-rich foods with structured fiber themes per session. AHA diet: follow American Heart Association dietary guidelines including increasing fiber; energy intake goals calculated to achieve 1 to 2 lb/week weight loss (baseline calories minus 500 to 1000 kcal); personalized saturated fat allowance of 7% of calories; no physical activity recommendations.

At 12 months, weight loss was similar: high fiber -4.6 lb; AHA -6.0 lb (difference 1.4 lb; not significant). Waist circumference reduction favored AHA by 0.5 inches. Total caloric intake decreased in both groups; greater reduction with AHA (-464.6 kcal/day) than high fiber (-200 kcal/day). The high fiber group improved insulin resistance and fasting insulin by 12 months (lower HOMA-IR and fasting insulin). Blood pressure decreased in both groups with no between-group differences. No meaningful differences in lipids or inflammatory markers. A fiber-focused diet can achieve clinically meaningful weight loss similar to the AHA diet and may improve insulin resistance, suggesting single-component dietary messaging can be a viable alternative to multi-component guidelines in metabolic syndrome.

Generalizability limited: predominantly white, well-educated women; baseline fiber and dietary quality higher than national average; results may not apply to more diverse or higher-risk populations; reliance on self-reported dietary data; some diabetes classification considerations during the trial.