Diet beverages match water in 493-adult weight trial

A 104-week randomized study found little difference between water and diet beverages for managing weight over time. The research involved 493 adults with overweight or obesity, all enrolled in a structured behavior-based program. Each person was assigned either commercially sold diet drinks or water as a daily beverage. By the study’s end, weight loss was similar in both groups, as was the ability to maintain it.

The findings also offered no evidence that the tested beverages impaired appetite control or created lasting metabolic problems. Both groups recorded gains beyond body weight, including smaller waist measurements, changes in body composition and improvements across several metabolic indicators. The results appeared in the British Journal of Nutrition.

The American Beverage Association paid for the study, while the researchers reported retaining authority over the data analysis and publication. Led by Jo Harrold of the University of Liverpool and Jason Halford of the University of Leeds, the trial adds clinical evidence to an ongoing policy debate. Current World Health Organization guidance discourages relying on sugar substitutes to manage body weight, partly because earlier observational evidence left questions unresolved. The authors said this longer randomized research could contribute to later public-health recommendations.