A two-year study found similar results for people drinking either beverage while managing their weight
A study of 493 adults found that diet drinks and water supported similar weight-loss results over two years.
Participants in both groups maintained weight loss, even after a year without regular support from a weight-management program.
The findings suggest diet drinks can be an alternative to sugary beverages without putting weight-loss progress at a disadvantage compared with water.
If you're trying to lose weight, choosing what to drink can feel like another decision to get right. Water is a common choice, but what about diet soda and other drinks sweetened without sugar? Can they fit into a weight-management plan, or is water a better option?
Researchers at the University of Liverpool examined that question in a long-term clinical trial published in the British Journal of Nutrition. The study compared beverages containing non-nutritive sweeteners low- or no-calorie alternatives to sugar with water to see how each affected weight loss and the ability to maintain it.
The research also addresses questions about whether these sweeteners affect appetite or contribute to weight gain over time. The findings offer a longer-term look at how diet drinks compare with water, although they don't mean every beverage choice will produce the same results for everyone.
This study provides the longterm clinical evidence that has been missing from international discussions, researcher Professor Jason Halford said in a news release. For people trying to manage their weight, nonnutritive sweetened beverages offer an effective alternative to sugarsweetened drinksand perform equivalently to water over two years.
How researchers compared water and diet drinks
The SWITCH trial included 493 adults with overweight or obesity. Researchers randomly assigned participants to one of two groups: one drank water, while the other consumed commercially available diet beverages.
Participants were asked to drink at least two servings of their assigned beverage daily. The diet drinks contained sweeteners such as aspartame, acesulfame potassium, and sucralose.
The study lasted 104 weeks, or two years, and included three stages. Participants first completed a 12-week weight-loss program with weekly group meetings. They then moved into a 40-week weight-maintenance phase with monthly support. Finally, they entered a 52-week period of monitoring without the same ongoing assistance.
Researchers measured changes in body weight and other health indicators over time. Of the original 493 participants, 220 completed the full two-year period.
What the results mean for consumers
At the end of the study, participants who drank water had lost an average of 3.7 kilograms (about 8.2 pounds), while those who drank diet beverages had lost 4.8 kilograms (about 10.6 pounds). The difference was not statistically significant, meaning researchers did not find a meaningful difference between the two groups' weight-loss results.
Both groups also maintained their weight loss through the two-year period. Researchers reported improvements in waist and hip measurements, body composition, and several health markers in both groups. Sugar intake decreased in both groups, with a slightly larger reduction among those drinking diet beverages.
For consumers, the takeaway is that water wasn't the only beverage associated with successful long-term weight management in this study. Diet drinks performed similarly, suggesting they may be a reasonable alternative for people looking to cut back on sugary drinks.
There are some limitations to keep in mind. The trial took place at a single location in England, and relatively few participants completed the full two years. The study also examined beverages alongside a structured weight-management program, rather than in isolation.
The findings don't establish that diet drinks are better than water, nor do they mean everyone needs to consume artificially sweetened beverages. Instead, they provide evidence that, for adults participating in a weight-management program, choosing diet beverages rather than water did not lead to significantly different weight-loss results over two years.
Posted: 2026-10-26 16:05:08









