Diet drinks containing sugar substitutes were found to be as effective as water for supporting weight loss in overweight or obese adults, according to a two-year randomized trial.
The study, led by the University of Liverpool, England, included 493 participants aged 18 to 65 with a body mass index (BMI) between 27 and 35, indicating they were overweight or obese. Participants were divided into two groups: one received 22.3 ounces of water daily, while the other received the same amount of diet soda or other low-calorie sweetened beverages for 104 weeks. The diet beverage group consumed drinks with sweeteners like aspartame, acesulfame potassium, and sucralose.
After two years, individuals in the diet beverage group lost an average of 10.6 pounds, while those who drank water lost approximately 8.2 pounds. Both groups maintained a significant amount of weight loss even after the structured support ended, and showed reductions in waist and hip measurements, as well as body fat, with no substantial differences between the groups. Total cholesterol levels remained within healthy ranges for both participants.
Experts emphasize that the effectiveness of diet drinks in this study is linked to their role as a substitute within a comprehensive weight-management program. Alix Turoff, a registered dietitian not involved in the study, noted that the findings do not suggest that diet beverages have a unique metabolic effect but rather that they can help reduce overall calorie intake if they replace sugar-sweetened beverages. "If someone normally drinks 250 calories of regular soda and switches to zero-calorie soda, then they’re saving calories," she explained.
The study did not find significant differences in hunger levels or sugar intake between the groups, addressing concerns that artificial sweeteners might increase appetite. Turoff stated, "I would still recommend water as the primary hydration choice, but I don’t think people need to be afraid of diet drinks because they think they will automatically prevent fat loss or cause weight gain."
Limitations of the research include its single-location setting in England and the fact that only 220 of the initial 493 participants completed the full 104-week assessment. The voluntary nature of the second-year extension may have also selected for more motivated participants. The study was funded by the American Beverage Association, though the authors asserted the association did not influence the study's design, data analysis, or interpretation of results.