Do sweeteners increase hunger?

What effect do sweeteners have on our brain? The same as sugar? And is it the same for everyone? Let's say right away that it is not possible to generalize the answers, but for some time now some studies have suggested that zero-calorie sweeteners can have the "side effect" of increasing hunger. The list is now joined by research from the Keck School of Medicine of the University of Southern California (USA) and the University of Tübingen (Germany) published in Nature Metabolism .

The experiment

Using magnetic resonance imaging, researchers observed what happened in the brains of 75 people of normal weight, overweight, and obesity after consuming three beverages: water containing sucralose, a sweetener widely used in Europe (identified with the code E955); water containing a dose of table sugar (sucrose) that gave the same degree of sweetness; or just water.

The Differences Between Sweetener and Sugar in the Brain

Well, acute consumption of sucralose increased the activity of the hypothalamus (a region of the brain that, among other things, regulates the sense of satiety) more than did sugar consumption. In the first case, participants also reported an increase in appetite, which did not occur in the second. And this effect was amplified in obese people compared to those of normal weight.

“Compared to sucrose and water,” the researchers write in the study, “sucralose increases functional connections between the hypothalamus and brain regions involved in motivation and sensory processing. These results suggest that noncaloric sweeteners may influence key mechanisms in the hypothalamus responsible for regulating appetite. The effect may depend not so much on the specific sweetener but on the sweet taste itself, which activates sweet taste receptors throughout the body.”

“Sweet Neurons” and the Expected Calories Hypothesis

As one of the authors, Stephanie Kullmann of the Institute for Diabetes Research and Metabolic Diseases at the Helmholtz Center Munich at the University of Tübingen, explains in an interview with Medscape , we know that the brain contains sensitive sensors that detect blood glucose levels and that there are neurons that respond specifically to sweetness. The suspicion, she says, is that the brain gets confused: "We have learned to expect that a sweet taste in the mouth signals real sugar and, therefore, calories. But sweeteners do not provide those calories. This discrepancy probably triggers the expectation that something else is coming, which in turn stimulates appetite." Furthermore, as expected, sugar consumption increased blood sugar levels and hormones such as insulin and GLP-1, which are implicated in the sense of satiety, while sucralose did not.

The results therefore leave open the hypothesis that zero-calorie sweeteners - in this case sucralose (which is being re-evaluated by EFSA , the European Food Safety Authority) - can influence food-related behavior. To say this with certainty, however, much more research is needed and it is not yet clear whether what was observed is also valid for "natural" sweeteners such as stevia, the researcher emphasizes.

Are obese people more sensitive to sweets?

What surprised the researchers, however, was the difference in responses between the three groups studied: "People with obesity - he emphasizes - reacted more markedly to the sweet taste than normal-weight participants, regardless of whether the drink contained calories or not". A gender difference also emerged: the effect was stronger for women than for men.

Don't accustom children to the sweet taste

A whole other chapter to investigate concerns the interactions between sweeteners and sugar and sweeteners and food in general. For Kullmann there is a basic problem: exposure to sweet flavors from early childhood and which leads to the development of habits that are harmful to health. Another factor to consider is the belief that low-calorie products are automatically healthier.