Highlights
- A new big study confirms a useful role for low/no calorie sweeteners in weight management, when used in place of sugar, and adds further clarity as to when their use brings value.
- Studies comparing low/no calorie sweeteners with water or placebo find no difference on impact on body weight. This proves that sugar substitutes do not cause weight changes by themselves and that their benefits relate to sugar, hence calorie, reduction in the diet, in line with their intended use.
- The bigger the displacement of sugar in the diet, the greater the beneficial effect of low/no calorie sweeteners’ use.
The new study by Rogers and Appleton1 is the second systematic review and meta-analysis on low/no calorie sweeteners and weight management published this year. Together with the study by Laviada-Molina and colleagues2, published in March 2020, they are the two most thorough systematic reviews on this topic to date. The main conclusion of both reviews is that the consumption of low/no calorie sweeteners versus sugar can help decrease body weight by reducing daily energy intake, while there is no impact on weight outcomes when there is no calorie reduction, for example when sweeteners are compared to water or placebo. Importantly also, this new review adds further clarity on how and when low/no calorie sweeteners can help in weight loss by providing answers to three key questions related to sweeteners and weight management.
What does this new study show?
The new study looked at three research questions:
- How do low/no calorie sweeteners affect energy intake and body weight when compared with sugar? (i.e. when sweetness remains the same but there is a difference in energy content between the intervention and the control groups).
- How do low/no calorie sweeteners affect energy intake and body weight when compared with water or nothing? (i.e. where there is no meaningful difference in energy content between groups while there is a difference in taste); and
- How do low/no calorie sweeteners (in capsules) affect energy intake and body weight when compared with placebo capsules? (i.e. where there is no meaningful difference in energy content between groups, and no difference in taste).
The results of the meta-analyses showed that:
- Body weight, body mass index (BMI) and energy (calorie) intake were reduced by consumption of low/no calorie sweeteners compared with sugar. Additional analysis showed that the more sugar is removed from the diet, the greater the impact is. The study found that for every 1 MJ (approx. 240 kcal) of energy replaced by low/no calorie sweeteners, body weight decreases by ~1.06 kg in adults. This effect of sugar dose shows that the primary means by which sweeteners reduce body weight is by reducing energy intake.
- There was no difference between low/no calorie sweeteners and water/nothing in their impact on body weight and BMI, while the analysis showed mixed results for energy intake. These results refute claims suggesting that exposure to sweet taste without calories may increase body weight.
- Similarly, no difference was found in energy intake or body weight when low/no calorie sweeteners in capsules were compared with placebo capsules. These results add evidence to the notion that low/no calorie sweeteners have no impact on appetite or on energy balance by, for example, affecting the gut hormones.
Why do some reviews reach different conclusions when looking at the same evidence?
Looking at the totality of the available evidence is always important. By comparing the results of this study with the outcomes of the five previously published systematic reviews and meta-analyses, three earlier studies found clear evidence that consumption of low/no calorie sweeteners in place of sugar can help reduce body weight.2-4 This is in line with the findings of the meta-analysis by Rogers and Appleton.1 On the other hand, two other reviews5,6 were equivocal about the effect of sweetener consumption on body weight. A closer examination however reveals important differences in the numbers of studies included in each of these reviews (for example, the Toews et al review6 includes only 5 studies vs 60 in Rogers and Appleton1), and/or how studies are grouped incorrectly in the meta-analyses (for example, both Azad et al5 and Toews et al6 analysed together studies with different comparators – sugar or water or placebo).
Why this systematic review is the most complete to date
Systematic reviews and meta-analyses of controlled human studies provide the highest quality of evidence in nutrition research. Therefore, the publication of this new study is important news.
The publication by Rogers and Appleton provides the most recent systematic review and includes all published studies until June 2020. Furthermore, it represents the largest work to date including meta-analyses of 60 articles that report 88 randomised controlled trials with a duration of over 1 week.
Additionally, the importance of this new study is that it analyses current data taking into consideration plausible biological and behavioural mechanisms, and is framing the right research questions, i.e. how low/no calorie sweeteners may affect body weight when compared to different caloric (sugar) or non-caloric comparators (water, nothing, placebo).
A dietitian’s remark
Low/no calorie sweeteners are food ingredients with sweet taste and no, or practically no, calories. As food ingredients, they should not be expected to provide health benefits on their own or act as magic bullets in weight loss. Their intended use is to replace sugar in foods and beverages while maintaining sweet taste with fewer or zero calories. Therefore, it makes sense that their benefits in weight management are related to the reduction of sugars and calorie intake in the context of a balanced diet and lifestyle. In fact, this is exactly what the latest review by Rogers and Appleton shows. They are one among several means that can help people reduce their overall calorie intake, and in turn lose weight.
