Researchers from Maastricht University and the University of Copenhagen have found that using sweeteners and sweetness enhancers in a healthy, low-sugar diet can help adults with overweight or obesity keep off lost weight for up to a year.
The findings were published in Nature Metabolism and showed changes in gut bacteria that may support better digestion and overall health.
Worldwide, rising rates of overweight and obesity are increasing the risks of diseases like type 2 diabetes and heart problems.
Experts say that diets high in sugar and unhealthy fats are a big part of the problem. That’s why the World Health Organization suggests people limit their intake of added sugars to under 10% of daily energy—and ideally under 5%.
Sweeteners and sugar alternatives have been debated for years. Some studies suggested they might lead to weight gain, while others found no harm or even some benefits.
This new research, called the SWEET study, aimed to find out if swapping sugary foods and drinks with sweetener-based products could help with long-term weight maintenance. It also looked at whether this change would affect the gut microbiome—the collection of bacteria in our digestive system.
The study included 341 adults and 38 children from four European cities: Athens, Copenhagen, Maastricht, and Pamplona. After two months of losing weight on a low-calorie diet, participants were randomly assigned to two groups for a 10-month maintenance phase.
One group followed a diet low in sugar but avoided sweeteners, while the other group replaced sugary items with products containing sweeteners or sweetness enhancers (S&SEs).
The sweeteners used were typical commercial options like aspartame, stevia, sucralose, and sugar alcohols such as erythritol and xylitol. Participants could choose which products to use, and researchers did not test the effects of individual sweeteners.
Adults in the S&SE group lost more weight than those in the sugar group. After one year, the S&SE group had lost about 1.6 kg more on average.
People who followed the diet more closely lost even more—about 3.7 kg more than those who didn’t stick to the guidelines. The group using sweeteners also reduced their sugar intake by about 12 grams per day more than the other group.
The researchers also saw changes in gut bacteria. In the S&SE group, there was an increase in bacteria known to produce short-chain fatty acids (SCFAs), which are helpful for digestion and overall health.
These included genera like Megasphaera, Prevotella, and Eubacterium. There was also a rise in bacteria that produce methane, such as Methanolobus.
Some other bacteria decreased in the S&SE group, such as Saccharimonadales and Candidatus Competibacter. These shifts suggest that sweeteners might help create a healthier gut environment.
The researchers also found increased signals for helpful fermentation and vitamin production in the gut, along with less activity in pathways related to fat remodeling.
Health markers like cholesterol and BMI showed some early improvement in the S&SE group, but by the end of the year, most differences had evened out, except for a greater drop in hip size. Liver fat levels were similar between the groups, and children showed some weight improvement with no major differences between the two diets.
However, the S&SE group reported more minor digestive issues, such as gas, stomach pain, and loose stools, though these were not considered serious.
In conclusion, the study suggests that using sweeteners and sweetness enhancers in a sugar-reduced, healthy diet is a safe and effective way for adults to maintain weight loss over a year. It may also help shift gut bacteria in a positive direction.
There were no major health concerns, though some people may experience mild digestive discomfort. For children, both diets led to small weight improvements with no major differences.
If you care about gut health, please read studies that your gut can help lower your blood pressure: here’s how and from shock to awe: a zap in the gut could be the new insulin for people with diabetes.
For more about gut health, please read studies about a surprising link between gut health and eye disease risk and Gut troubles could signal future Parkinson’s disease.
The study is published in Nature Metabolism.
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