A review of three European studies published in Nutrients finds non-nutritive sweeteners (NNSs) do not hinder weight loss or health outcomes, according to a 2025 analysis led by researchers at the University of Ljubljana and Wageningen University & Research, supported by the Institute for the Advancement of Food and Nutrition Sciences (IAFNS).
The review, which pooled data from the SWEET, SWITCH, and Sweet Tooth trials, found that replacing sugar with NNSs did not impede weight loss or maintenance. In a one-year SWEET trial, participants who used NNSs maintained slightly greater weight loss than those who avoided them, particularly among the most adherent individuals. The 52-week SWITCH trial showed NNS-sweetened beverages led to marginally more weight loss than water, though the difference was not clinically significant. The Sweet Tooth trial, which manipulated dietary sweetness without a weight-loss goal, found no meaningful impact on body weight or composition.
Metabolic markers such as blood sugar, insulin, blood pressure, cholesterol, and liver enzymes remained stable across groups. Some studies noted smaller post-meal blood sugar spikes with NNSs, and a minor shift in gut bacteria was observed but not linked to worsened cardiometabolic risk. The review also found no evidence that NNSs increased cravings for sugary foods; in fact, participants who avoided sweeteners developed a stronger preference for sweetness over time.
Non-nutritive sweeteners may aid sugar reduction without affecting weight
The analysis focused on three large, multi-year randomized controlled trials (RCTs) designed to isolate cause-and-effect relationships. The SWEET consortium, funded by the EU’s Horizon 2020 program, examined weight-loss maintenance. The SWITCH trial, backed by the American Beverage Association, compared NNS-sweetened beverages to water. The Sweet Tooth study, supported by the Dutch government’s TKI Top Sector Agri-Food scheme, manipulated dietary sweetness exposure without a weight-loss objective.
Researchers emphasized the studies’ limitations: results primarily apply to overweight adults in structured programs, and self-reported dietary data may be prone to underreporting. Some outcomes were secondary or exploratory, and dropout rates were higher than ideal in certain trials. Graham Finlayson, a University of Leeds researcher, noted that concerns about NNSs increasing sweetness preferences or appetite were not validated by the trials. A common concern is that replacing sugar with non-nutritive sweeteners might lead to a stronger preference for sugary sweet foods or stimulate appetite. Across these controlled studies, that prediction was not supported,
he said, according to the review.
The review was supported by IAFNS’ Low- and No-Calorie Sweeteners Committee, with funding from the EU, the American Beverage Association, and Dutch public-private partnerships. The research team included scientists from the University of Ljubljana, Wageningen University & Research, and the University of Leeds, alongside collaborators in the Netherlands, Denmark, Spain, and Belgium. The underlying SWEET, SWITCH, and Sweet Tooth studies were funded respectively by the EU’s Horizon 2020 program, the American Beverage Association, and the Dutch government’s TKI Top Sector Agri-Food public-private partnership scheme, together with private-sector contributions.
No Evidence That Sugar Substitutes Harm Weight, Health, Or
Public health guidance on NNSs remains divided. The World Health Organization (WHO) has advised caution, recommending overall reduction in dietary sweetness, while some UK-based groups view NNSs as a legitimate tool for cutting sugar intake. The review highlights a broader tension between RCTs, which often show neutral or favorable effects, and observational studies that report health risks—often confounded by pre-existing metabolic conditions in participants.
The findings underscore the need for tailored recommendations, as results may not apply to children, individuals with different metabolic profiles, or real-world eating patterns outside structured programs. Researchers caution against overgeneralizing the results and call for further studies on long-term effects and diverse populations.
Impacts of non-nutritive sweeteners on the human microbiome
The review adds to ongoing debates about NNSs, but its impact on policy will depend on how regulatory bodies incorporate RCT evidence alongside observational data. With the WHO and other agencies continuing to refine guidelines, the study provides a critical data point for balancing public health messaging.
Future research may focus on long-term safety, effects on children, and interactions with other dietary factors. The review’s authors stress that NNSs are not a weight-management strategy by itself but can provide a useful way to reduce sugar while retaining sweetness within a broader healthy diet. They also note that the studies’ findings do not support claims that NNSs lead to stronger preference for sugary foods or stimulate appetite. Sweeteners are not a weight-management strategy by themselves, but they can provide a useful way to reduce sugar while retaining sweetness within a broader healthy diet,
according to the review.
Readers are advised to consult qualified professionals for personalized guidance, as the evidence does not support generalizing the results to all populations. The studies’ focus on overweight adults in structured programs limits their applicability to broader contexts. The review emphasizes the importance of distinguishing between RCTs and observational studies, which often reflect different methodologies and confounding factors. By highlighting the need for further research, the study contributes to the evolving understanding of NNSs and their role in public health strategies.
