Non-sugar sweeteners: why the WHO advised against using them for weight loss

Non-sugar sweeteners, such as aspartame, sucralose, saccharin, acesulfame K and stevia, give a sweet taste with few or no calories. They are found in "diet" or "zero" drinks, chewing gum, yoghurts, desserts and sweetener tablets for coffee. The logic seemed simple: less sugar, fewer calories, less weight.

The 2023 guideline

In May 2023 the World Health Organization published a guideline advising against using non-sugar sweeteners as a means of weight control or of reducing the risk of non-communicable diseases. The guideline was based on a systematic review of the evidence.

• In short clinical trials, replacing sugar with sweeteners led to a small reduction in weight.
• But there was no evidence of a long-term benefit in reducing body fat in adults or children.
• In long-term observational studies, high use of sweeteners was linked with a slightly higher risk of type 2 diabetes, cardiovascular disease and mortality. These links may be partly explained by the fact that people at higher risk use them more.

The WHO called the recommendation "conditional", because the evidence was of low quality, and stressed that it does not apply to people who already have diabetes.

Aspartame

In July 2023 the International Agency for Research on Cancer placed aspartame in group 2B, "possibly carcinogenic", based on limited evidence. The same day, the WHO and FAO expert committee JECFA confirmed that the acceptable daily intake remains 40 milligrams per kilogram of body weight. This means that a 70-kilogram adult would have to drink many cans of "diet" drinks a day to exceed it. Both assessments said more studies are needed.

The problem is not only sugar. It is training our taste to constant sweetness.

What you can do

1. Gradually reduce sweetness in general, not just sugar. Taste adapts within a few weeks.
2. Water, unsweetened tea and unsweetened coffee remain the best everyday drinks.
3. If you drink sugary drinks, switching to the "zero" version can be an intermediate step, but not the destination.
4. Whole fruit gives sweetness together with fibre and vitamins.