Studies Show Diet Sodas May Not Be Stalling Weight Loss as Much as Previously Thought

Artificially sweetened drinks are often demonized based on the theory that they may encourage a greater appetite, or supercharge our sugar cravings, but recent work appears to dispel the bad rap around diet sodas and gaining weight. Now, a two-year clinical trial from the University of Liverpool, England, has provided the greatest insight yet, into the long-term effects of diet drinks on weight loss.

The groundbreaking study, conducted over the course of 104 weeks and published in the British Journal of Nutrition, attempted to build on a similar report in 2023 that also found no proof for the theory that diet sodas can stall weight loss.

Do Diet Drinks Cause Weight Gain or Cravings? What the 2-Year SWITCH Trial Proves

While both studies pitted water against zero and low-calorie drinks that were free of sugar (also known as non-nutritive, or NNS beverages) the continued efforts to find the true value of diet drinks is critical, because sugar sweetened beverages often account for a substantial source of dietary sugar, excess calories, and an increased risk of type 2 diabetes. So, if science can show that NNS drinks do not lead to increased sugar intake or excess appetite, they could instead play a part in a balanced diet. To that end, the Liverpool University study has been described as the longest, most comprehensive trial in this area to date. “This study provides the long‑term clinical evidence that has been missing from international discussions,” explained Professor John Halford, who was lead author on the project.

2-Year Clinical Trial Comparison: Diet Drinks vs. Water

493 overweight or obese adults were entered into a structural weight management program and then split into those who only drank water, and those who consumed a choice of 20 commercially available diet drinks containing aspartame, sucralose, and acesulfame.  Each drink contained less than 2.1 calories per 100ml, with no overall daily calorie cap on drinks. The NNS group were allowed to drink water, but they were asked to drink at least two 330ml servings per day of a diet beverage.

Interestingly, neither group was not blocked from drinking sugary beverages, but they did received coaching to reduce them.

What were the results after 104 weeks?

•   Weight loss difference between NNS and water groups deemed insignificant
•   Both groups maintained sustained weight reduction for the full 2 years
•   Both groups saw reductions in waist size along with improved body composition

The study also found that overall sugar intake decreased slightly greater in those drinking the NNS beverages, seemingly disproving the theory that artificially sweetened drinks encourage sugar cravings, and suggesting the opposite effect may occur.

“These latest findings show that concerns about sweeteners disrupting appetite or causing weight gain are not supported when tested in a rigorous, long-term randomized trial,” said Professor Harrold. “We hope this evidence informs future WHO guidance and public health policy.”