A two-year randomized clinical trial involving 493 adults with overweight or obesity found that diet drinks performed about as well as water for long-term weight loss, with no evidence of increased appetite or metabolic harm. Conducted by researchers at the University of Liverpool, the study compared weight outcomes between participants who consumed diet beverages and those who drank water, aiming to assess the role of low-calorie sweeteners in weight management over an extended period.
The trial, which ran from 2024 to 2026, required participants to follow a structured weight-loss program while being assigned to either drink water or diet beverages as their primary low-calorie drink option. Researchers monitored changes in body weight, waist circumference, blood pressure, and markers of metabolic health at regular intervals. Both groups received identical dietary and behavioral counseling, ensuring that the only variable was the type of beverage consumed. Adherence was tracked through self-reports and periodic biomarker checks to validate intake.
Participants who drank diet beverages did not report higher levels of hunger or cravings compared to the water group, countering concerns that artificial sweeteners might stimulate appetite. Blood tests showed no significant differences in insulin sensitivity, lipid profiles, or liver function between the two groups over the study period. Weight loss averaged approximately 5 to 6 kilograms in both groups by the end of the trial, with similar rates of weight regain observed during follow-up phases. Researchers noted that the lack of adverse metabolic effects supports the safety of diet drinks as a tool for calorie reduction when used as part of a broader lifestyle intervention.
While neither group maintained all lost weight after the active intervention phase, the study suggests that diet drinks do not hinder long-term weight management when substituted for sugary alternatives. The findings challenge the notion that low-calorie sweeteners undermine weight loss through biological feedback mechanisms. Instead, they indicate that beverage choice may be less critical than overall dietary adherence and behavioral support. Experts caution that individual responses can vary and that diet drinks should not be seen as a standalone solution but as one option within a comprehensive approach to healthy eating.
Did diet drinks cause any negative health effects in the trial? No, the study found no evidence of increased appetite, worsened metabolic markers, or other adverse effects linked to diet drink consumption over the two-year period.
Was the weight loss difference between groups statistically significant? No, the average weight loss in the diet drink and water groups was nearly identical, with no statistically significant difference observed.
Should people replace water with diet drinks for weight loss? The results suggest diet drinks can be a viable alternative to water for those seeking to reduce calorie intake from beverages, but they should be used alongside healthy eating and physical activity, not as a substitute for them.