Science news from the 14th European Nutrition Conference – FENS 2023
- Two large year-long clinical trials presented at FENS 2023 indicate improved weight loss maintenance with the use of low/no calorie sweeteners
- These new findings are in line with outcomes of systematic reviews and meta-analyses of randomised controlled trials that report a modest but significant reduction in body weight with the use of low/no calorie sweeteners when compared with sugars
- The inconsistency between results of randomised controlled trials and those of observational studies were discussed by academic experts at the ISA scientific symposium at FENS 2023
The leading European conference on nutrition took place this year in Belgrade, Serbia, from 14th to 17th November 2023. Organised every four years by the Federation of European Nutrition Societies (FENS), the 14th European Nutrition Conference – FENS 2023 featured symposia, oral and poster presentations on the role of low/no calorie sweeteners in our diet, including a scientific symposium organised by the International Sweeteners Association (ISA).
Key remarks from the ISA scientific symposium
Chaired by Prof Alison Gallagher, Ulster University, UK, and with the participation of academic experts as panel speakers, the ISA scientific symposium aimed to provide latest evidence and a platform for scientific discussion on the topic of “Low/No Calorie Sweeteners as a Tool in Reducing Sugars Intake, Body Weight and Risk of Non-Communicable Diseases (NCDs): From Evidence to Recommendations.”
Findings of recent systematic reviews on low/no calorie sweeteners and weight control, including from a study by the World Health Organization (WHO), were discussed by Prof Katherine Appleton, Bournemouth University, UK. Systematic reviews and meta-analyses of randomised controlled trials (RCTs) report a beneficial effect of low/no calorie sweeteners on reducing energy intake, leading in turn to modest weight loss, when compared with sugars, while no effects are observed when compared with water or placebo.1-3 While evidence from RCTs consistently report a beneficial effect on body weight, some observational studies report positive associations between higher low/no calorie sweetener intake and risk of obesity or related non-communicable diseases (NCDs).3
The inconsistency between evidence from RCTs and observational studies was discussed at the ISA symposium by Prof Carlo La Vecchia, University of Milan, Italy. Modest associations between low/no calorie sweeteners’ intake and obesity or vascular diseases from observational studies with relative risks of the order of 1.1-1.3 do not allow inference on causation since bias and confounding cannot be excluded. Reverse causation is not quantifiable and is a key issue in this topic, meaning that people with overweight or obesity may preferably be turning to low/no calorie sweeteners as a sugar reduction strategy leading to a spurious association between sweeteners’ intake and higher body weight. Rating evidence from observational studies as of very low/ low certainty, WHO identified that efforts are needed to address reverse causation.
From evidence to recommendations
The different interpretation of the evidence base is evident in recent recommendations. Based on evidence from RCTs, the USDA 2020-2025 Dietary Guidelines for Americans support that replacing added sugars with low/no calorie sweeteners may reduce calorie intake in the short-term and aid in weight management.4 In contrast, based largely on observational cohort studies with single dietary intake data lacking repeated measures, the WHO issued a conditional recommendation suggesting that non-sugar sweeteners not be used as a means of achieving weight control or reducing the risk of NCDs.5
However, people change their diets over time. Therefore, evidence from observational studies with single, baseline sweeteners’ intake data, lacking repeated measurement of exposure over time, is hardly interpretable, especially since prospective cohort studies with repeated measures report different results. A meta-analysis of 14 prospective studies with repeated measures and change or substitution analyses indicated no adverse associations but a modest cardio-metabolic benefit of substituting sugar-sweetened beverages with low/no calorie sweetened alternatives.6 This is consistent with the findings from RCTs.
New research presented at FENS 2023
Findings of two new, large, year-long randomised controlled trials were also presented at the conference indicating the benefits of low/no calorie sweeteners’ use in long-term weight control. While following different study designs, both the SWITCH trial and the long-term clinical trial of the European Commission Horizon 2020 funded SWEET project found that consuming low/no calorie sweeteners during and following a weight loss period, can help individuals maintain the lost weight off over a period of one year.
The SWEET project’s long-term trial, a 1-year multicentre RCT in 330 adults with overweight or obesity aimed to assess the impact of low/no calorie sweeteners’ use as part of a healthy diet on weight loss maintenance and metabolic health.7 Following an initial 2-month period in which adults consumed a low-energy diet with the aim to achieve ≥5% weight loss, participants were then randomised to follow a healthy ad libitum diet with or without low/no calorie sweetened products for another 10 months. Primary outcome results presented at the conference suggest that weight loss maintenance was slightly better in the sweetener versus the sugar group (1.6kg more weight loss with the use of low/no calorie sweetened products), with the full results expected to be published soon in scientific journals.
The findings from the SWEET project are in line with results from another long-term RCT in adult participants with overweight or obesity, the SWITCH trial, which was also presented at FENS 2023 conference. Published results of this clinical trial showed a similar, modest but significantly greater weight loss maintenance with low/no calorie sweetened drinks compared with water after following a one-year weight loss and weight maintenance programme (1.4kg more weight loss with the use of low/no calorie sweetened beverages).8 This study is still ongoing, with the results of a third phase of voluntary, unassisted weight maintenance at 2 years of follow-up expected next year.
Practical considerations for weight management
Although the approximately 1.5 kg greater weight loss maintenance with low/no calorie sweeteners’ use over one year may seem modest, we need to consider this effect in the context of a wider weight management effort where the use of low/no calorie sweeteners is only one among a pool of dietary strategies that aim at energy intake reduction. In the case of sweeteners, research shows that their benefit is greater the more sugar is removed from the diet.1 It is therefore reasonable to expect that people who consume a high amount of added sugars in their diet will have the greater benefit in energy intake reduction, and hence in weight loss, when they replace sugar-sweetened with low/no calorie sweetened products.