BACKGROUND/OBJECTIVE: There is little randomised evidence using a whole food plant-based (WFPB) diet as intervention for elevated body mass index (BMI) or dyslipidaemia. We investigated the effectiveness of a community-based dietary programme. Primary end points: BMI and cholesterol at 6 months (subsequently extended). SUBJECTS: Ages 35-70, from one general practice in Gisborne, New Zealand. Diagnosed with obesity or overweight and at least one of type 2 diabetes, ischaemic heart disease, hypertension or hypercholesterolaemia. Of 65 subjects randomised (control n=32, intervention n=33), 49 (75.4%) completed the study to 6 months. Twenty-three (70%) intervention participants were followed up at 12 months. METHODS: All participants received normal care. Intervention participants attended facilitated meetings twice-weekly for 12 weeks, and followed a non-energy-restricted WFPB diet with vitamin B12 supplementation. RESULTS: At 6 months, mean BMI reduction was greater with the WFPB diet compared with normal care (4.4 vs 0.4, difference: 3.9 kg m-2 (95% confidence interval (CI)±1), P<0.0001). Mean cholesterol reduction was greater with the WFPB diet, but the difference was not significant compared with normal care (0.71 vs 0.26, difference: 0.45 mmol l-1 (95% CI±0.54), P=0.1), unless dropouts were excluded (difference: 0.56 mmol l-1 (95% CI±0.54), P=0.05). Twelve-month mean reductions for the WFPB diet group were 4.2 (±0.8) kg m-2 BMI points and 0.55 (±0.54, P=0.05) mmol l-1 total cholesterol. No serious harms were reported. CONCLUSIONS: This programme led to significant improvements in BMI, cholesterol and other risk factors. To the best of our knowledge, this research has achieved greater weight loss at 6 and 12 months than any other trial that does not limit energy intake or mandate regular exercise.