Abstract
BACKGROUND: Plant-based caloric restriction diet (PB-CRD), combining plant-based nutrition with intermittent caloric restriction, represent a structured dietary strategy to obesity management. This study compared the effects of PB-CRD and calorie-restricted diet (CRD) on weight loss, and metabolic health, hypothesizing that PB-CRD is non-inferior to CRD for weight loss. METHODS: In this 12-week, open-label, non-inferiority trial, 80 participants with obesity (body mass index [BMI]: 28-40 kg/m(2), age: 18-45 years) were randomized in a 1:1 ratio to either a PB-CRD ('5 + 2' pattern: 5 days/week of provided standardized plant-based meals and 2 days/week of self-selected meals within prescribed caloric targets) or a CRD (7 days/week of self-selected meals within prescribed caloric targets). Both groups adhered to the same daily energy intake targets of 1,600 kcal/day (men) and 1,300 kcal/day (women). The primary outcome was weight loss, while secondary outcomes included body composition, glucose and lipid metabolism, liver and kidney function, oxidative stress, and inflammation markers. RESULTS: Of the 80 participants (mean BMI: 32.03 ± 3.46 kg/m(2); mean age: 34.78 ± 7.12 years; 31 males), 52 (65%) completed the 12-week trial (n = 28 in PB-CRD and n = 24 in CRD group). Both groups achieved significant within-group weight loss from baseline (p < 0.05): 5.11 kg in the CRD and 6.56 kg in the PB-CRD group. The between-group difference was -1.44 kg (95% confidence interval [CI]: -3.27 to 0.39), which remained within the pre-specified non-inferiority margin of 0.5 kg. Compared to the CRD, the PB-CRD group demonstrated significantly greater between-group reductions in total body fat percentage (2.96 [95% CI: 1.67-4.25], p = 0.028), uric acid, and superoxide dismutase levels, as well as increased blood urea nitrogen (p < 0.05). Additionally, the PB-CRD group exhibited significant within-group improvements in visceral fat mass, HOMA-IR, total cholesterol, liver function markers, and inflammatory markers (p < 0.05), with no substantial differences between groups. CONCLUSION: Both PB-CRD and CRD were effective for weight loss, with PB-CRD demonstrating non-inferiority. Furthermore, PB-CRD offered superior benefits in reducing total body fat and improving uric acid metabolism, while improving insulin sensitivity and liver function in adults with obesity. CLINICAL TRIAL REGISTRATION: Identifier ChiCTR1800015156.