Sweeteners cut sugar intake without weight or metabolic harm, review counters WHO advice

A narrative review suggests that substituting sugar with non-nutritive sweeteners (NNSs) does not impact weight loss, with blood sugar and metabolic markers remaining stable in various studies. It suggests that NNSs can help reduce sugar consumption without having a negative impact on health, while countering the popular belief that sweet diets lead to sweetness cravings. 

European researchers examined three consortia from the region to answer questions about whether NNSs and sweet-tasting foods affect weight, metabolic health, and taste preferences over time.

Nutrition Insight speaks with a study co-author, Dr. Graham Finlayson, professor of Psychobiology at the University of Leeds, UK, to learn about the review’s strengths and weaknesses, as well as how the findings compare with WHO’s advice against sweetener consumption for weight management.

Public sweetener guidance

The Institute for the Advancement of Food and Nutrition Sciences (IAFNS), which supported the review’s publication, points out that public guidance on sugar substitutes is inconsistent. 

IAFNS explains that varying perceptions about NNSs’ health impacts can be traced to a disparity between randomized controlled trials and observational studies.The WHO, for instance, advises against sweeteners for weight control and suggests reducing overall sweetness in the diet. The US Dietary Guidelines for Americans (2025–2030) take a “real food” stance, discouraging the intake of highly processed foods, including NNSs.

Also, many professional groups — the British Dietetic Association, the British Nutrition Foundation, and Diabetes UK — support NNSs for cutting sugar intake.

According to the IAFNS, the disparity can be traced back to randomized controlled trials, which have shown neutral or beneficial effects, and observational studies that report more health risks. The associations in the latter studies can be misread since people already facing higher metabolic risk tend to consume more sweeteners, it adds.

To address the mixed findings from previous studies, the new review examined evidence from large, multiyear, multicenter randomized trials that aimed to isolate cause-and-effect relationships.

Weight management findings

All three consortia suggest that consuming NNSs instead of sugar did not undermine weight loss and even helped in some cases. 

The one-year weight-loss-maintenance trial from the SWEET consortium showed that participants who included NNSs in their diet maintained modestly greater weight loss than those who avoided them. 

The 52-week SWITCH trial revealed that participants drinking the NNS-sweetened beverages experienced slightly more weight loss than those drinking water, but IAFNS notes the difference was just under being clinically meaningful.

All three consortia suggest that consuming NNSs instead of sugar did not undermine weight loss and even helped in some cases.Meanwhile, the Sweet Tooth trial altered dietary sweetness without having a weight loss goal and found that it had no meaningful impact on body weight or composition.

Metabolic health and taste findings

In terms of metabolic and cardiovascular markers, the review points out that blood sugar, insulin, blood pressure, cholesterol, liver enzymes, and related biomarkers were generally stable and similar in sweetener and non-sweetener groups.

In short-term tests, the review notes that replacing sugar with NNSs was linked to smaller post-meal blood sugar and insulin spikes. Additionally, in one sub-study, a modest change in gut bacteria composition was observed, without worsening of cardiometabolic risk markers.

On the sweet taste preference examination, the review did not find evidence that consuming sweeteners or a sweeter diet generally causes people to crave more sweetness or eat more. Conversely, the SWEET trial revealed that participants who avoided sweeteners developed a stronger liking for sweet foods over time — this was not the case for those consuming NNSs. 

According to Finlayson, the team is unsure why sweetener-avoiders developed a stronger sweet tooth over time, adding that this finding should not be used to make formulation decisions.

“I think the finding that exposure to sweeteners did not increase liking or wanting for sweet foods challenges the conception that consuming sweeteners trains people to want progressively sweeter diets.”

Additionally, the researchers note that across the three trials, hunger, cravings, and actual food intake measures were similar regardless of sweetener use or its exposure level.

Balancing bias in funded research

The consortia SWEET, SWITCH, and Sweet Tooth 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.

“The individual trials were designed, conducted, analyzed, and published by the respective research teams, and the funders had no role in those studies or interpretation of the results,” says Finlayson, explaining how the research team guarded against bias.

“IAFNS supported the subsequent review in Nutrients but had no role in steering the scientific content or interpretation, and the studies themselves had already been carried out before IAFNS became involved.”

IAFNS suggests that the three consortia represent some of the most “rigorous experimental evidence to date” on the health impacts of NNSs. Together, their findings support swapping sugar with alternatives for weight management strategies without harming metabolic health. 

Quality and duration of trials

The three trials showed neutral to favorable effects. Finlayson notes that since the trials were carried out over specific time periods, it is difficult to know whether they were long enough to catch potential long-term harms. 

Finlayson says that the review should be considered when WHO updates its guidance on NNSs.“Even though randomized trials give stronger evidence about cause and effect, even the longer trials only extend to around a year, so they can’t rule out effects that might emerge after many years of exposure.”

“Observational studies can examine much longer periods, but can’t easily separate the effect of sweeteners from the reasons people choose them,” he says. “For example, people at greater risk of obesity or diabetes may be more likely to switch to low-calorie products. So, neither evidence source is definitive on its own.”

Finlayson adds that the review’s trials bring reasonably strong evidence that the negative effects of NNSs sometimes found were not present in the period tested experimentally so far.

Considerations for the WHO

When considering the review’s contradiction of WHO guidance against sweeteners for weight loss, Finlayson points out that the WHO’s take is a conditional population-level recommendation based on its review of the wider literature that includes observational evidence.

“Our review concentrates on these three recent randomized controlled trials designed to test specific causal hypotheses,” he notes. “Our findings, therefore, add newer experimental evidence (after the WHO’s conditional guidance) that should be considered when it is next updated.”

“We would expect guidance to evolve if a larger body of longer-term randomized controlled trials’ evidence consistently shows that replacing sugar with sweeteners produces benefits without causing metabolic or behavioral harms,” he concludes.