Two-Year Trial Finds Diet Drinks No Worse Than Water for Weight Control
A randomized study followed 493 adults with excess weight or obesity for two years as they either drank water or commercially available diet beverages while receiving behavioral weight-management support. At the end of the trial, the diet-drink group had lost about 4.8 kilograms and the water group about 3.7 kilograms, a difference that was not statistically significant. Both groups kept weight off over the second year and showed similar improvements in waist and hip size, body composition, and metabolic health, with no meaningful differences in blood pressure or cholesterol.
Researchers randomly allocated 493 adults with excess weight or obesity to two years of either water or store-bought diet drinks. Both groups also joined a structured behavioral weight-management program. The diet drinks used aspartame, acesulfame-K, and sucralose, all within European Food Safety Authority safety limits.
The results build on the SWITCH trial, published in 2023 in the International Journal of Obesity; the newer paper appeared in the British Journal of Nutrition. The American Beverage Association paid for the peer-reviewed study, but the investigators kept authority over data analysis and reporting. The World Health Organization has cautioned against non-sugar sweeteners as a weight-control tool, citing unclear evidence from observational studies.
These findings may influence how clinicians, policymakers, and consumers view diet drinks in weight management. People seeking lower-sugar options could feel more confident choosing them, while those wary of sweeteners may remain cautious. Because the trial included behavioral support, results may not translate to drinking diet beverages alone. Future guidance from bodies such as WHO could shift if longer-term randomized evidence accumulates.