Abstract
OBJECTIVES: Investigate the impact of a 10-week whole-food plant-based (WFPB) community programme on weight and type 2 diabetes up to 36 months postintervention. DESIGN: Randomised waitlist-controlled trial. SETTING: Community-based General Practice clinic classified as 'Very Low-Cost Access' in Gisborne, the main city of the Tairāwhiti region of New Zealand. PARTICIPANTS: Adults (n=56) aged 30-72 years, with obesity (Body Mass Index (BMI) ≥30) and glycated haemoglobin (HbA1c≥40 mmol/mol) in the last 6 months. Of the participants, 59% identified as Māori and 5% as Pasifika. INTERVENTION: A 10-week programme consisting of 2 hours, two times per week sessions (40 hours total), involving skills-based learning and health education. PRIMARY AND SECONDARY OUTCOME MEASURES: Primary measures were changes in weight, BMI and HbA1c. Secondary measures included changes in cholesterol, waist circumference, exercise levels, plant-based and non-plant-based dietary scores and association with Big Five Inventory personality traits. The primary endpoint was assessed at post-treatment (10 weeks), with follow-up at 6 and 36 months postintervention. RESULTS: Differences between the intervention and waitlist control groups at 10 weeks were compared with independent samples t-tests. In intention-to-treat analyses, the intervention group demonstrated significantly greater weight loss of 3.3 kg (95% CI (0.8 to 5.7), p<0.001) and a non-significant trend of 3.2 mmol/mol HbA1c reduction (CI (-0.4 to 6.7), p=0.08). Between-group differences post-treatment were not statistically significant for cholesterol (p=0.69), waist circumference (p=0.16) or activity level (p=0.97). After all participants received the intervention, repeated-measures ANOVAs were used to assess changes over time; significant omnibus effects were followed by paired-sample t-tests comparing baseline with subsequent time points. In this larger intervention group, some significant reductions were observed: weight loss was present post-treatment and sustained at 3 kg at 36-month follow-up (CI (1.2 to 4.7), p<0.001). Waist circumference decreased by 6 cm post-treatment and was sustained. HbA1c dropped by 3.3 mmol/mol and cholesterol by 0.4 mmol/L post-treatment, but decreases were not sustained at follow-up time points (HbA1c results were possibly limited by inadequate data capture). Simple linear regression models found that greater dietary adherence related to better outcomes: increased WFPB food intake and decreased non-WFPB intake corresponded with greater weight loss post-treatment (unstandardised regression coefficients=0.3-0.4, p values <0.04). CONCLUSIONS: This 10-week WFPB diet community intervention decreased weight, BMI, HbA1c and cholesterol. The intervention produced a weight loss of 5 kg post-treatment, with 3 kg weight loss sustained at 36 months. TRIAL REGISTRATION NUMBER: This trial was prospectively registered with the Australian New Zealand Clinical Trials Registry (https://anzctr.org.au); ACTRN12617000541303, date of registration 07/04/2017.