Drinking sugar-free beverages while dieting may help you shed pounds and maintain your weight loss – and is just as beneficial as drinking water – a new study says.
Researchers wanted to test if regularly drinking a diet beverage makes it harder to lose or maintain weight loss.
The study compared two groups of overweight adults that were assigned to drink water or artificially sweetened drinks throughout their weight loss journey.
Sweeteners used in the study included aspartame, which is found in popular sodas such as Diet Coke and Diet Pepsi.
For two years, participants took part in a behavioral weight-loss program designed to help them shed pounds and keep it off. They received guidance from a nutritionist and gradually increased their physical activity until they were exercising for an hour six days a week.
Researchers found both teams weighed less than they did at the start of the study. In fact, diet soda drinkers lost 25 percent more weight than those who stuck to water.
The findings suggest sugar-free drinks could offer a low-calorie way to satisfy a craving for something sweet, potentially making weight-management plans easier to stick to.
Experts caution that more research is needed, however, adding that some studies have linked artificial sweeteners to long-term health issues such as diabetes and heart disease.
A two-year experiment comparing diet drinks with water during a calorie deficit found that people drinking artificially sweetened beverages did not gain more weight than those drinking water
Artificial sweeteners such as aspartame and sucralose are about 200 times sweeter than sugar and have zero calories.
They are typically found in diet sodas, as well as sugar-free energy drinks including Celsius.
While it’s long been clear that sugar raises the risk of heart disease, obesity, and diabetes, the long-term effects of artificial sweeteners – especially on weight loss – remain unclear.
In the August 2026 study, published in the British Journal of Nutrition, researchers tested the ongoing debate about whether non-sugar sweeteners actually help with long-term weight control.
Experts studied 493 adults between the ages of 18 to 65, and their body mass index (BMI) was between 27 and 35, which is categorized as overweight and obese.
Of the subjects, 246 were randomly assigned to drink water and 247 were assigned to drink diet or sugar free drinks.
Participants were instructed to consume at least two 330 millilitre (ml) servings, about 2.7 cups, every day of their assigned beverage.
The zero-sugar group had a choice of 20 commercially available beverages, including diet colas, diet carbonated soft drinks, diet fruit drinks and diet fruit-flavored waters.
The main artificial sweeteners in them were aspartame, acesulfame potassium and sucralose. These are commonly used in Diet Coke products and zero-calorie sweeteners such as Splenda.
People assigned to water were told to avoid artificially sweetened beverages entirely, including zero-calorie sweeteners added to hot drinks. The diet-drink group could still drink water in addition to their assigned beverages.
Participants were then put into a weight loss program that had three stages: active weight loss, supported weight maintenance and no weight management sessions.
The above chart compares body weight over weeks 50 to 104 of the experiment in two groups: one that drank water and one that drank non-nutritive sweeteners, otherwise known as artificial sweeteners. The artificial sweetener group lost slightly more weight by the end
After two years, both groups weighed less than what they started. Water drinkers lost about 8.2lbs from their starting weight, while diet-drinkers lost 10.6lbs – a 2.4lb difference
The program involved one-hour group sessions each week, led by a nutritionist who provided guidance on eating behaviors, structured nutrition and physical activity.
For the first year, participants were told to progressively increase their physical activity by adding 10 minutes of walking to their daily routine until they reached 60 minutes of activity on six days each way.
The researchers monitored their activity and step count using fitness trackers.
From weeks zero to 12, participants attended the weekly nutrition sessions. During this period, both groups lost weight quickly.
From weeks 13 to 52, they transitioned from weekly to monthly sessions to help maintain their weight loss. The water group reached its lowest weight at week 44, while the diet-drink group reached its lowest at week 36.
And from weeks 53 to 104, they continued their journey on their own, while tracking their designated drinks. By the final week, both groups remained significantly lighter than before.
After two years, both groups weighed less than what they started. Water drinkers lost about 8.2lbs from their starting weight, while diet-drinkers lost 10.6lbs – a 29 percent difference.
Both groups had significantly smaller waist and hip circumferences than when they started, with their waists down by about two inches.
The researchers also performed more detailed body-composition scans on a small subset of 48 participants, which discovered both groups lost fat and some lean tissue at similar rates.
They also took fasted blood samples from participants to measure their blood pressure, glucose, cholesterol, and insulin levels.
Total cholesterol rose slightly in the diet drink group, while a long-term blood sugar measure called HbA1c increased slightly with diet drinks but stayed about the same with water.
Diastolic blood pressure, the lower number in a reading, fell more among water drinkers. However, these results were based on just 14 to 16 people per group, and none of the differences were considered medically significant.
While the diet-drinkers lost more weight, researchers could not say that diet drinks were responsible for greater long-term weight loss. The groups were considered equivalent in terms of their weight outcomes.
Researchers also tested a long-held theory about artificial sweeteners confusing the body’s relationship between sweetness and calories – potentially increasing appetite and causing people to compensate by eating more.
The findings did not show a meaningful difference in hunger between the two groups.
One limitation of the study was while 493 people started, only 220 completed the 104-week endpoint.
By the end, there were 117 in the water group versus 103 in the diet drink group. The researchers did statistical analyses designed to account for missing data, and these also found no significant weight loss difference between the two beverages.
Enrollment took place between 2016 and 2021, so the COVID-19 pandemic disrupted some follow-up visits.
The trial found no evidence that choosing diet drinks over water derailed their progress.