Extended follow-up of a short total diet replacement programme: results of the Doctor Referral of Overweight People to Low Energy total diet replacement Treatment (DROPLET) randomised controlled trial at 3 years

Objectives To test the long-term effectiveness of a total diet replacement programme (TDR) for routine treatment of obesity in a primary care setting. Methods This study was a pragmatic, two-arm, parallel-group, open-label, individually randomised controlled trial in adults with obesity. The outcomes were change in weight and biomarkers of diabetes and cardiovascular disease risk from baseline to 3 years, analysed as intention-to-treat with mixed effects models. Interventions The intervention was TDR for 8 weeks, followed by food-reintroduction over 4 weeks. Behavioural support was provided weekly for 8 weeks, bi-weekly for the next 4 weeks, then monthly for 3 months after which no further support was provided. The usual care (UC) group received dietary advice and behavioural support from a practice nurse for up to 3 months. Results Outcome measures were collected from 179 (66%) participants. Compared with baseline, at 3 years the TDR group lost −6.2 kg (SD 9.1) and usual care −2.7 kg (SD 7.7); adjusted mean difference −3.3 kg (95% CI: −5.2, −1.5), p < 0.0001. Regain from programme end (6 months) to 3 years was greater in TDR group +8.9 kg (SD 9.4) than UC + 1.2, (SD 9.1); adjusted mean difference +6.9 kg (95% CI 4.2, 9.5) P < 0.001. At 3 years TDR led to greater reductions than UC in diastolic blood pressure (mean difference −3.3 mmHg (95% CI:−6.2; −0.4) P = 0.024), and systolic blood pressure (mean differences −3.7 mmHg (95% CI: −7.4; 0.1) P = 0.057). There was no evidence of differences between groups in the change from baseline to 3 years HbA 1c (−1.9 mmol/mol (95% CI: −0.7; 4.5; P = 0.15), LDL cholesterol concentrations (0.2 mmol/L (95% CI −0.3, 0.7) P = 0.39), cardiovascular risk score (QRISK2) (−0.37 (95% CI −0.96; 0.22); P = 0.22). Conclusions Treatment of people with obesity with a TDR programme compared with support from a practice nurse leads to greater weight loss which persists to at least 3 years, but there was only evidence of sustained improvements in BP and not in other aspects of cardiometabolic risk.