Non-nutritive sweetened beverages versus water after a 52-week weight management programme: a randomised controlled trial

BACKGROUND/OBJECTIVE: Sugar-sweetened beverages are a major source of added sugar and are linked to weight gain and metabolic disease. Dietary guidelines recommend water or non-nutritive sweetened (NNS) beverages to reduce sugar intake, but long-term randomized controlled trials (RCTs) are limited. This study compared NNS beverages with water on body weight during weight loss and maintenance within a behavioral weight management program. METHODS: In a parallel-group, open-label, controlled equivalence RCT, adults (BMI 27–35 kg/m²) who regularly consumed cold beverages were randomized 1:1 to water or NNS beverages. Participants attended weekly sessions during a 12-week weight-loss phase and monthly sessions during a 40-week weight-maintenance phase. The primary endpoint was weight change at week 52 (equivalence tested with two-sided p > 0.05). Secondary endpoints included anthropometrics, cardiometabolic biomarkers, appetite, sweetener/sugar intake, and activity. RESULTS: Of 493 randomized (water n=246; NNS n=247), 24.1% were NNS-naïve. At week 52, groups were non-equivalent, with significantly greater weight loss in the NNS group: −6.1 kg (water) vs −7.5 kg (NNS); between-group difference 1.4 kg (90% CI 0.2, 2.6); p < 0.05. CONCLUSIONS: Over 52 weeks, NNS beverages led to statistically greater weight loss maintenance than water, though the difference was not clinically significant. CLINICAL TRIAL REGISTRATION: NCT02591134.