Do low-calorie sweeteners help with weight management? And are they safe for long-term use?

This is among the most controversial topics in nutritional science. In early May 2023, the World Health Organization issued a statement that cautions against the use of nonsugar sweeteners for weight loss except for people who have preexisting diabetes.

The WHO based its new recommendation on a 2022 systematic review and meta-analysis of scientific studies on nonsugar sweetener consumption in humans. This type of study reviews a large body of research to draw a broad conclusion.

Based on its interpretation of that large-scale review, the WHO recommended against using artificial sweeteners for weight control and concluded that there may be health risks associated with habitual consumption of nonsugar sweeteners over the long term. However, the WHO also acknowledged that the existing evidence is not conclusive and that more research needs to be done.

As neuroscientists, we study how dietary factors such as sweeteners affect the brain’s ability to perform critical functions, including metabolism, appetite, and learning and memory.

We found the WHO’s advisory surprising based on the study’s equivocal results. Determining the answers to these questions is immensely challenging, and public health messaging around recommendations can send mixed messages.

Natural sugars like glucose and fructose, together with fiber and other nutrients, are found in many food sources that are considered healthy, such as fruit. However, these simple carbohydrates have been increasingly added into manufactured food products, especially beverages. Sugar-sweetened beverages are usually high in calories and offer little else in the way of nutrition.

In the early 20th century, food and beverage manufacturers began incorporating naturally and chemically derived substances that satisfy sweet cravings but contain significantly fewer calories than natural sugars – and, in some cases, zero calories. Sugar substitutes became particularly widespread in the 1950s with the increasing popularity of diet sodas. Since then, consumers have increasingly turned to these sugar substitutes in their everyday lives.

Sugar substitutes go by many names, including high-intensity sweeteners, artificial sweeteners, nonnutritive sweeteners, low-calorie sweeteners and, as termed in the WHO report, nonsugar sweeteners.“ These include synthetic compounds like sucralose, acesulfame potassium and aspartame, and naturally derived ones, such as those from the plant Stevia rebaudiana, among many others.

Each nonsugar sweetener has a unique chemical structure, but they all activate sweet taste receptors at very low concentrations. This means that you need to add only a tiny amount of them to sweeten your coffee or tea, as opposed to heaping spoonfuls of natural sugar.

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