European trials find non-nutritive sweeteners do not undermine weight loss

Researchers from the University of Ljubljana, Wageningen University & Research and the University of Leeds have reviewed evidence from three major European trials examining whether non-nutritive sweeteners (NNSs) affect weight management, metabolic health and preferences for sweet foods. The review found that replacing sugar with NNSs did not undermine weight loss or maintenance and did not appear to increase appetite or cravings for sweet foods.

Published in the peer-reviewed journal Nutrients, the analysis examined findings from the SWEET, SWITCH and Sweet Tooth consortia, which investigated sweetener use and dietary sweetness under controlled conditions.

Professor Graham Finlayson of the University of Leeds said the findings did not support concerns that replacing sugar with NNSs could increase preferences for sweet foods or stimulate appetite.

“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. 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.”

Graham Finlayson, Professor, University of Leeds

 

What the European trials found

In a one-year SWEET weight-loss maintenance trial, participants who included NNSs in their diets maintained modestly greater weight loss than those who avoided them, with the largest differences seen among participants who adhered most closely to the intervention.

A 52-week SWITCH trial found that people drinking NNS-sweetened beverages lost slightly more weight than those drinking water, although the difference was not considered clinically meaningful. The Sweet Tooth trial, which altered dietary sweetness without a weight-loss goal, found no meaningful impact on body weight or body composition.

The review also found that blood glucose, insulin, blood pressure, cholesterol, liver enzymes and related metabolic markers were generally comparable between sweetener and non-sweetener groups. Some shorter-term tests found smaller post-meal increases in blood glucose and insulin when sugar was replaced with sweeteners.

Altogether, the researchers saw no evidence that NNSs or a generally sweeter diet caused people to develop stronger preferences for sweet foods. Hunger, cravings and actual food intake were largely similar across the trials. In the SWEET trial, participants who avoided sweeteners developed a stronger liking for sweet foods over time while those who used sweeteners did not.

What the findings mean for sugar reduction

The findings come amid an ongoing debate over NNSs. The World Health Organization has cautioned against relying on non-sugar sweeteners for weight control and suggested reducing overall dietary sweetness, while other professional groups, including several in the UK, regard NNSs as a tool for reducing sugar intake.

The authors say that observational studies can report different associations from randomised controlled trials and that these associations may be influenced by existing health risks among people who consume sweeteners.

However, the researchers caution that the evidence has limitations. The trials mainly involved overweight adults in structured programmes, while some outcomes were secondary or exploratory. Self-reported dietary intake is also prone to underreporting.

The authors stress that null findings do not prove NNSs have no effects under any circumstances. Long-term effects, particularly among children and adolescents, remain unclear. However, overall, the review suggests replacing sugar with NNSs may help reduce sugar intake without apparent harm to weight management or metabolic health over the periods studied.