Sweeteners — what the science says

In a nutshell

When sweeteners replace sugar, people lose about a kilo; compared with water, they have no advantage.^2,3
WHO does not recommend sweeteners as a weight-loss tool; according to its review, long-term use is linked with a higher risk of diabetes and heart disease.⁴
Aspartame is safe up to 40 mg per kilo of body weight a day — a 70 kg person would have to drink more than 9–14 cans of diet soda to exceed it.⁵

1What sweeteners are

Non-sugar sweeteners are tens to hundreds of times sweeter than sugar, so only tiny amounts are needed and they provide almost no energy. The WHO recommendation covers acesulfame K, aspartame, advantame, cyclamates, neotame, saccharin, sucralose and stevia, but not sugar alcohols (polyols) such as erythritol or xylitol.⁴

How much sugar is still fine is covered in the article Sugar.

2Do they help with weight loss?

Moderate evidence −1.1 kg A summary of studies lasting at least a week: when sweeteners replaced sugar, people ate less energy and lost 1.1 kg more (29 studies with 2,267 people). Compared with water or nothing, there was no difference.²

Moderate evidence 17 studies A summary of 17 randomised trials with 1,733 overweight adults: replacing sugary drinks with sweetened drinks reduced weight by 1.1 kg and body fat percentage. The result pointed in the same direction as replacing them with water.³

Weak evidence 56 studies A review of 56 studies: for most health outcomes, people who used sweeteners did not differ from those who did not. A small benefit for BMI and blood sugar came from a few small studies with low certainty.¹

3Why WHO is cautious

WHO recommendation conditional WHO (2023) advises against using sweeteners for weight control or disease prevention. According to its review, they bring no long-term weight loss, and long-term use may be linked with a higher risk of type 2 diabetes, heart disease and death. The recommendation is conditional and does not apply to people who already have diabetes.⁴

But associations from observational studies may be biased: people who already have excess weight or higher risk drink sweetened drinks more often. Instead of sweeteners, WHO advises gradually reducing the sweetness of the diet.⁴

4Aspartame and erythritol

WHO and IARC assessment 40 mg/kg In 2023, the International Agency for Research on Cancer (IARC) classified aspartame as “possibly carcinogenic” (Group 2B) based on limited evidence for liver cancer. At the same time, the JECFA expert committee confirmed the acceptable daily intake of 40 mg per kilo of body weight: a 70 kg person would exceed it only with more than 9–14 cans of diet soda a day.⁵

Weak evidence — observational and small study 1.8–2.2× Among people examined for heart problems, those with the highest blood erythritol had a 1.8–2.2 times higher risk of heart attack, stroke or death within 3 years than those with the lowest. In 8 healthy volunteers, erythritol from a drink raised blood levels to a level that increased platelet clotting in the lab. This does not prove cause and effect yet.⁶

What to take from this

Drinking sugary sodas? Switching to the “zero” version helps you cut sugar.^2,3
Water remains the best choice; you can gradually get used to less sweetness.^3,4
There is no need to fear aspartame in normal amounts.⁵
In ForkRep, sugars count towards a daily cap; sweeteners are not among them.

Sources

Written on 9 Oct 2026, based on studies available at that date. Newer research may change the conclusions.

Toews I. et al. (2019). Association between intake of non-sugar sweeteners and health outcomes: systematic review and meta-analyses of randomised and non-randomised controlled trials and observational studies. BMJ 364:k4718. doi.org/10.1136/bmj.k4718
Rogers P. J., Appleton K. M. (2021). The effects of low-calorie sweeteners on energy intake and body weight: a systematic review and meta-analyses of sustained intervention studies. Int J Obes 45:464–478. doi.org/10.1038/s41366-020-00704-2
McGlynn N. D. et al. (2022). Association of low- and no-calorie sweetened beverages as a replacement for sugar-sweetened beverages with body weight and cardiometabolic risk: a systematic review and meta-analysis. JAMA Netw Open 5:e222092. doi.org/10.1001/jamanetworkopen.2022.2092
World Health Organization (2023). WHO advises not to use non-sugar sweeteners for weight control in newly released guideline (press release). who.int
World Health Organization (2023). Aspartame hazard and risk assessment results released (press release). who.int
Witkowski M. et al. (2023). The artificial sweetener erythritol and cardiovascular event risk. Nat Med 29:710–718. doi.org/10.1038/s41591-023-02223-9

This is general information and does not replace a doctor or dietitian. If you have phenylketonuria, you must avoid aspartame.