Drinks sweetened without sugar performed as well as water for long-term weight management in a two-year randomised trial of 493 UK adults. The SWITCH trial, run at the University of Liverpool with the University of Leeds, was published online in the British Journal of Nutrition on 4 August 2026 (DOI 10.1017/S0007114526108150). Liverpool publicised the long-term results on 29 September and wider coverage followed in early October. Participants had a body mass index of 27 to 35 and were randomised 1:1 to water (246 people) or to non-nutritive sweetened beverages (247 people) alongside a group behavioural weight-management programme of 52 weeks of assisted meetings followed by 52 weeks of unassisted monitoring. At week 104 the water group had maintained a weight loss of 3.7kg against 4.8kg in the sweetened drinks group, a difference the authors report as not significant. The trial was funded by the American Beverage Association, which the paper says had no role in the design, conduct or analysis but could review the manuscript before publication.
What the trial does and does not settle
The design was open-label, so participants knew which drink they had been allocated, and only 220 of the 493 completed the final unassisted year, 117 on water and 103 on sweetened drinks. Everyone took part in a structured behavioural programme, so the result describes the two drinks within that programme rather than drinking habits on their own. The sweeteners used were aspartame, acesulfame potassium and sucralose, at levels the researchers say sit within established European safety limits. Both groups also reduced waist and hip measurements, and the university reports no clinically meaningful differences in blood pressure or cholesterol.
What this means in practice
Professor Joanne Harrold of the University of Liverpool said: "These latest findings show that concerns about sweeteners disrupting appetite or causing weight gain are not supported when tested in a rigorous, long-term randomised trial." Co-lead Professor Jason Halford of the University of Leeds said the study "provides the long-term clinical evidence that has been missing from international discussions". The trial compared two drinks in people already enrolled on a weight-management programme. It did not test any food supplement, and it offers no basis for claiming that a product aids weight loss. Readers reviewing their wider health spending can browse Perqen's full product catalogue.
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Sources
- Major trial examines no-sugar sweetened soft drinks - University of Liverpool
- Effect of non-nutritive sweetened beverages v. water on body weight: long-term results of a randomised controlled trial - Cambridge Core
- Effect of non-nutritive sweetened beverages v. water on body weight: long-term results of a randomised controlled trial - British Journal of Nutrition
- Diet drinks work as well as water for weight loss, major trial finds - ScienceDaily