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Replacing sugar with sweeteners can improve weight loss control over the long-term in adults in the overweight range, finds European randomised controlled trial
· European randomised controlled trial also finds that adults with overweight consuming food and drinks with no/low-energy sweeteners reported greater diet satisfaction, more positive mood, and lower cravings and explicit liking for sweet foods compared to those avoiding sweeteners.
· Importantly, long-term use of sweeteners did not raise the risk markers for type 2 diabetes or cardiovascular disease.
· No/low energy sweetened products may also benefit children with high levels of uncontrolled eating.
· The SWEET trial authors say the findings add to the ongoing debate on the use and safety of non-nutritive sweeteners for appetite and weight control.
Not peer-reviewed, randomised controlled trial, people
*This is an early press release from the European Congress on Obesity (ECO 2024) Venice 12-15 May. Please credit the Congress if using this material*
New research being presented at this year’s European Congress on Obesity (ECO) in Venice, Italy (12-15 May), suggests that replacing sugar-sweetened food and drinks with low/no energy sweetened products can help weight control for at least one year after rapid weight loss in adults, without increasing the risk of type 2 diabetes or cardiovascular disease.
The findings of a year-long randomised controlled trial involving adults with overweight and obesity and children in the overweight range from Northern, Central and Southern Europe, also found that consumption of sweeteners and sweetness enhancers (S&SE) was associated with greater diet satisfaction, more positive mood, and less cravings and explicit liking for sweet foods in adults.
The results come in the wake of a 2023 systematic review of the evidence by WHO which suggested that replacing free sugars with non-sugar sweeteners did not appear to help with weight control in the long term, and could raise the risk of various health problems including type 2 diabetes and cardiovascular diseases, although the report highlighted uncertainty around the evidence between sweeteners and disease outcomes [1].
“Weight maintenance after weight loss is difficult to achieve, and our findings support the use of S&SEs found in many foods and beverages worldwide as alternatives to sugar-sweetened products to help manage weight control in adults with overweight”, says trial lead author Professor Anne Raben from the University of Copenhagen in Denmark. “The findings also provide important information to address the controversies about potential adverse health effects. Until now, safety data have generally come from animal studies using sweetener doses far above the usual intake in humans.”
S&SEs have very high sweetening power but contribute little or nothing to energy intake. Natural and synthesised sweeteners, such as aspartame, stevia, and saccharin, are commonly added to products by the food and drink industry to cut the sugar content, and are consumed by millions of people around the world every day, for example in soft drinks, desserts, and breakfast foods.
However, the safety of these food additives and their use in appetite and weight control has been hotly debated, and little is known about the long-term effects of S&SE on eating behaviour.
Sweeteners show promise for weight control
To provide more evidence, researchers from the SWEET (Sweeteners and sweetness enhancers: Prolonged effects on health, obesity and safety) project, conducted a one-year randomised controlled trial to investigate whether the prolonged use of S&SEs as part of a healthy low-sugar diet could improve weight loss maintenance after rapid weight loss, as well as benefit risk markers for type-2-diabetes and cardiovascular diseases compared to no S&SE consumption.
Participants also completed questionnaires (at the start of the trial and after 2, 6 and 12 months) to assess the effect of S&SEs on diet satisfaction, control overeating, explicit liking and implicit wanting for food, eating behaviour, physical activity, and quality of life.
The trial recruited 341 adults with overweight or obesity (aged 18-65 years, 71% women, body mass index (BMI) ≥25 kg/m2), and 38 children with overweight (6-12 years, 60% girls, BMI-for-age >85th percentile) from Denmark, Spain, Greece, and The Netherlands through web pages, social media, newspapers and registries.
During the first 2 months of the trial, adults were instructed to follow a low-energy diet (the Cambridge Weight Plan) with the aim of achieving at least 5% weight loss. Children received dietary advice to maintain body weight.
In the following 10 months, participants were randomised to either a healthy diet with less than 10% of energy from added sugar allowing for foods and drinks with S&SEs (S&SEs group), or a healthy diet with less than 10% of energy from added sugar not allowing foods and drinks with S&SEs (sugar group).
At the start of the trial and after 2, 6, and 12 months, participants took part in clinical investigation days to measure change in weight, in BMI-for-age z-score in children (a measure of how many standard deviations a child’s BMI is above or below the average BMI for their age and sex), anthropometry, and risk markers for T2D (e.g., glucose and haemoglobin A1c) and CVD (e.g., cholesterol). Participants also completed food frequency questionnaires and urine samples were collected to measure biomarkers of S&SEs, fructose and sucrose to measure compliance [2].
As planned, intake of sugar-rich foods and beverages declined in both groups over the trial, but significantly more in the S&SE than in the sugar group. At the same time, intake of S&SE products increased in the S&SE group and declined in the sugar group. These results were confirmed by urinary biomarker analyses.
The intention-to-treat analyses (including 277 adults who successfully lost 5% or more body weight after the 2-month weight loss period) found that those consuming S&SEs had slightly better weight loss maintenance after 1 year than the sugar group (average weight loss of -7.2kg vs -5.6 kg making a difference of 1.6 kg).
Additionally, in 203 participants who completed all clinical investigations, risk markers for type 2 diabetes and cardiovascular disease did not differ between the groups.
No differences in BMI-for-age z-score or other outcomes were noted in the 22 children who completed the trial. A larger study would be required in more children to determine any potential effect, researchers say.
Sweeteners reduce cravings for sweet foods and improve well-being in adults
In further analyses of eating behaviour, researchers found that adults in the S&SE group reported greater diet satisfaction when eating out, increased positive mood, and lower craving for sweet food at 6 months than the sugar group. In contrast, adults in the sugar group had greater liking for sweet over savoury foods at 6 months and 12 months. However, there were no differences between the groups in reported physical activity or quality of life.
In children, replacing food and drinks with added sugar with sweetened products had no impact on eating behaviour or physical activity. However, inclusion of S&SEs appeared to benefit children with high levels of uncontrolled eating (eating in response to food palatability [tastiness] and the likelihood of over-consuming).
As co-lead author Ms Clarissa Dakin from the Appetite Control and Energy Balance Research Group at the University of Leeds, UK, explains, “Our findings suggest that the inclusion of low/no energy sweetened products may benefit children who show high levels of uncontrolled eating. For these children, being allowed to consume S&SEs led to lower levels of uncontrolled eating at 12 months in comparison to the children who were not allowed to consume S&SE’s. This benefit was not found for children with lower levels of uncontrolled eating. Together, these findings provide important insights for the ongoing re-evaluation of food additive sweeteners by the European Food Safety Authority and other health agencies worldwide.”
Professor Jason Halford, Head of the School of Psychology at the University of Leeds, UK, one of the SWEET co-authors and President of the European Association for the Study of Obesity (EASO), says, “'The use of low calorie sweeteners in weight management has been questioned, in part because of the link between their use and apparent weight gain in observational studies, however, increasingly it is becoming apparent that is not the case in long term studies.”
The authors note that a key strength of the study is that it is a10-month (long-term) investigation which adds to the evidence of previous short-midterm trials by using a weight loss maintenance design, including both foods and drinks with S&SEs, and by using daily amounts of intervention products that are feasible and realistic in an every-day life. In addition, the trial was conducted as a multicentre trial in four countries across Europe.
Nevertheless, they note some limitations of the study, including that the drop-out rate was larger than estimated. However, with 203 completers, the statistical power for the primary outcome was 86%, which is deemed satisfactory. Additionally, they say that the children’s results should be interpreted with caution because of the small number of participants. Finally, they considered S&SEs collectively without distinguishing between individual types, although this was done intentionally to reflect the variation of products in the market. Selection bias may also have been a factor, as more participants were women, had higher educational levels, and exhibited health-conscious behaviours.
This research represents the core randomised trial of the SWEET project. Prof Jo Harrold (University of Liverpool, UK), one of the SWEET project co-ordinators explains, “The EU Horizon2020 funded project has been developing and reviewing evidence on the long-term benefits and potential risks of replacing added sugar in the diet with S&SEs from multiple perspectives. The results of this long term trial support the use of S&SEs instead of sugar in food and beverages to aid weight control. The evidence suggests there are no grounds for concern in regard to the safety of these products on sweet preference, appetite, or glucose control. These results add to the body of evidence which indicates that S&SEs can play a positive role in weight management when used judiciously. Other aspects of the project have alluded to barriers that impede the development of healthier, low-energy products and a resulting need to review policy and regulatory approaches. The SWEET symposium will offer an opportunity to make industry representatives, consumers and policy makers aware of the potential benefits of S&SEs for public health and safety, obesity and sustainability.”
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Prof Kevin McConway, Emeritus Professor of Applied Statistics, Open University, UK
It’s one of the times of year when big scientific conferences occur, and so journalists and scientific commenters (like me) are faced with press releases on studies we can’t evaluate properly, because we just don’t get enough information. There is an abstract of a presentation that hasn’t happened yet, and a press release. But most details are missing. With most types of study, particularly those involving clinical trials (like this one), or systematic reviews or observational studies, the devil is in the detail, which we haven’t seen. It’s impossible to make a proper evaluation of the quality of the study’s conclusions without seeing more detail. We can’t even rely on there having been a peer review process. Usually (as here) the abstract of the presentation will have been through a review by the conference organisers, but they won’t have seen all the detail either. So I’m not going to waste my time and yours speculating about exactly what has been learned from this study.
For this particular study, the press release and the abstracts of the presentations are rather fuller than they sometimes are, so there is something to go on, but it really can’t do more than suggest that there might be something useful and interesting in the full research report, when we get to see it. Some results are given, though not every important detail. So, for example, we learn that the drop-out rate for the study was larger than expected. That might or might not be concerning. Detail on why and when people dropped out might tell us something about how acceptable the different diets were, or on whether some feature of the intervention caused problems for some participants – but we don’t know that.
One thing that we do know is that this study followed good practice by publishing a protocol in advance. In principle, that allows us to check whether the researchers did what they intended to do, and if not, why they didn’t. Changes to these protocols do happen reasonably often, usually for perfectly good reasons. The full report should give reasons for any changes and explain their consequences – but again we don’t have that. One possible change, that might have consequences, relates to the safety aspects of the trial – but it’s not even clear yet whether there was a change or not. More on that below.
The press release also says something interesting about the possible motivation for the trial. It refers to a 2023 systematic review by WHO of the health effects of non-sugar sweeteners. To summarise very crudely, that review found evidence from short-term clinical trials that using non-sugar sweeteners could be associated with lowering body weight, BMI total calorie intake and sugar intake, without much evidence of impact on disease diagnosis. But in data from observational studies, usually longer term, there was some evidence that BMI increased rather than decreasing with more use of non-sugar sweeteners, as well as increases in the risk of some diseases, particularly type 2 diabetes and cardiovascular disease. But the quality of the evidence behind most of these findings wasn’t high, particularly those from observational studies (which provided most of the evidence of possible harms). That review’s findings were fairly controversial at the time.
The press release implies that one of the reasons for the new trial is to deal with these shortcomings of the WHO review – or, at any rate, that we should reconsider the WHO findings in the light of the trial results. But I’m not sure that we can do that – though again I’ll have to wait for the full trial report to be sure.
One issue is that the new trial gets its data from a specific scenario. The participants began their involvement by two months of trying to lose at least 5 per cent of their body weight. Then the trial looked at how people’s success in maintaining their weight loss, over another 10 months, was associated with whether they had access to non-sugar sweeteners and sweetness enhancers. This does certainly seem to be something worth looking at, but the results will say something directly only about that situation of maintaining weight loss, after a period of quite rapid weight loss. What, if anything, this says about the use of non-sugar sweeteners for weight reduction in the first place isn’t clear, to me at least. Also this scenario is unlike what happened in most of the studies reviewed by WHO – so these new findings might well add to what WHO concluded, but won’t supersede it, I’d say.
I’m a bit more concerned about the safety aspects. The negative associations, found by WHO, between consumption of non-sugar sweeteners and the risk of some diseases, were found only in observational studies and generally only after differences in sweetener use had gone on for some considerable time. Is the length of this new trial long enough for associations with disease risk to show up? The protocol for the new trial says that these safety aspects would be measured primarily by measuring the populations of bacteria and microorganisms in the guts of the participants (the so-called gut microbiota). There would also be secondary measures of risk markers in the body for type 2 diabetes and cardiovascular disease (CVD). But nothing at all is said in the abstracts or the press release about microbes in the gut. Why not? This was the pre-registered measure of safety. Did they have to change this, and if so why? We aren’t told. Something is said about risk markers for diabetes and CVD – but only briefly. We are told that these markers did not differ between the participants who had access to the non-sugar sweeteners and those who did not – but only in those people who completed all the clinical investigations, and about a quarter of the participants did not complete them all. It’s quite possible that that doesn’t matter, but we can’t tell without more detail. Also, what’s more interesting than markers for diabetes and CVD is actual diagnoses of diabetes and CVD – but those diseases take time to develop, and the length of this trial might not be enough to show whether the risk increased or not.
In brief, it’s not clear whether this new trial can help to confirm or disconfirm the findings from that WHO review. The actual scenario it investigated is different from most of those reviewed by WHO, and what we know from the new trial about differences in disease risk really isn’t very clear (and is barely discussed in the information we have so far). We might know more after the full results are published, but now, it’s just too soon to say.
