By Modern HealthMe Team
Published: October 12, 2025
For years, artificial sweeteners have divided the nutrition world. Are they a harmless way to cut calories—or do they secretly interfere with metabolism and gut health?
A major new study published in Nature Metabolism suggests that sweeteners may actually help maintain weight loss and could even support a healthier gut microbiome—if used appropriately.
Researchers from the University of Copenhagen and several European centers followed 341 adults and 38 children with overweight or obesity for one year. Their goal was to see whether replacing sugar with sweeteners and “sweetness enhancers” (S&SEs) could make weight loss more sustainable and affect gut health.
Study Design
All adult participants first followed a two-month low-calorie diet, losing at least 5% of their body weight. Then, for ten months, they maintained a healthy, balanced diet with less than 10% of energy from sugars.
Half replaced sugary foods and drinks with products containing sweeteners such as aspartame, sucralose, or stevia, while the other half continued using sugar.
Results: Less Weight Regained, Healthier Gut
After one year, the sweetener group maintained an additional 1.6 kilograms (3.5 pounds) of weight loss compared to those who continued consuming sugar—a modest but meaningful advantage in long-term weight management.
The researchers also observed that participants who consumed sweeteners developed a different gut microbiome profile, with a greater abundance of bacteria producing short-chain fatty acids (SCFAs) such as acetate and butyrate. These compounds are known to reduce inflammation, support digestion, and may help regulate appetite and insulin sensitivity.
The gut bacteria of sweetener users showed higher methane and SCFA production, indicating a more metabolically active and potentially beneficial microbial environment. Importantly, there were no adverse effects on blood sugar, cholesterol, or liver enzymes.
“Our findings show that sweeteners can help maintain weight loss without negative effects on metabolism or gut health,” said Professor Anne Raben, senior author of the study. “They may help make a low-sugar diet easier to follow over time.”
Findings in Children
The study also included 38 children following similar dietary patterns. In this group, sweeteners showed neither strong benefits nor harms. Both groups had minor, healthy changes in body composition, reinforcing that moderation matters more than strict avoidance or overuse.
The Gut Health Connection
The gut microbiota—the trillions of microorganisms living in the intestines—play a central role in how the body processes food, stores fat, and manages blood sugar. Previous short-term or animal studies had raised concerns that sweeteners might disrupt this microbial balance.
However, this new trial—the largest and longest of its kind—suggests that at normal dietary levels, sweeteners may instead promote a more favorable gut environment.
Caution and Context
Not all sweeteners are identical, and individual gut responses can vary. Researchers emphasize that the benefits come when sweeteners replace added sugars within an overall healthy, nutrient-dense diet, not when they are used to justify more ultra-processed foods.
“Sweeteners can make a low-sugar diet more enjoyable and sustainable,” noted study co-author Dr. Louise Kjølbæk, “but they’re not a magic bullet.”
Why It Matters
With global obesity rates still rising, excess sugar remains a major public health concern. In 2023, the World Health Organization (WHO) advised against using artificial sweeteners for weight control, citing limited long-term evidence.
This new study—registered under ClinicalTrials.gov ID NCT04226911—provides strong counter-evidence, showing that sweeteners can be safe and effective tools for maintaining weight loss and supporting gut health.
The Takeaway
The SWEET study offers encouraging news for people aiming to reduce sugar intake. When incorporated sensibly into a balanced diet, sweeteners can:
- Help sustain weight loss
- Support beneficial gut bacteria and metabolic balance
- Pose no detectable health risks after one year
Moderation and overall diet quality remain key. Swapping sugar for a small amount of stevia or sucralose in your coffee may, according to new evidence, be a genuinely health-smart choice.