Abstract
The aim of this study was to provide robust evidence on the long-term use of non-nutritive sweetened (NNS) beverages on weight management, by comparing NNS beverages and water during 1 year of assisted weight management followed by a voluntary, unassisted 1-year extension. In this parallel-group, open-label, controlled equivalence trial, 493 adults with body mass index 27-35 kg/m2 who regularly consumed cold beverages were randomised 1:1 to water (n 246) or NNS beverages (n 247). Participants joined a group behavioural weight-management programme comprising assisted meetings weekly (12-week weight-loss phase) then monthly (40-week weight-maintenance phase), followed by unassisted monitoring for 52 weeks with a final meeting at week 104. The final 52 week unassisted phase was completed by 220 participants (water: n 117; NNS beverages: n 103), 27·7% of whom were NNS beverage-naïve (naïve was defined as NNS beverages comprising ≤ 25% of beverages in the 5 years before screening). In the unassisted monitoring phase, the primary endpoint was weight change from baseline at week 104 (equivalence: two-sided P > 0·05). Participants consuming water maintained a weight loss of 3·7 kg over 104 weeks, compared with 4·8 kg with NNS beverages; the between-group difference was not significant. After the final 52-week unassisted phase of the 104-week behavioural weight-management programme, water and NNS beverages showed equivalence regarding weight change from baseline. Our findings suggest people can lose weight, and maintain it for two years, when drinking either NNS beverages or water and taking part in weight-management programmes.
Summary
This paper reports the 104-week results of the SWITCH randomised controlled trial (RCT), in which 493 adults with overweight or obesity were randomised to consume at least two daily servings of low/no calorie sweetened beverages or water, alongside a behavioural weight-management programme. The intervention comprised 12 weeks of active weight loss, 40 weeks of assisted weight maintenance and a voluntary 52-week unassisted extension. At week 104 (end of second year of unassisted follow-up), both groups maintained significant weight loss from baseline, with a mean reduction of 4.8 kg with low/no calorie sweetened beverages versus 3.7 kg with water.
The two groups were equivalent in terms of weight change, with no significant between-group difference, and no statistically significant or not clinically relevant differences in health biomarkers.
These findings build on the earlier SWITCH results published by Harrold and colleagues in 2024, which showed significantly greater weight loss with low/no calorie sweetened beverages than water at week 52.
Overall, the SWITCH trial provides high quality evidence that low/no calorie sweeteners can be an effective tool to manage body weight over the long term, when used alongside a behavioural weight-management programme.