Artificial sweeteners are virtually calorie-free and are increasingly being used in the food industry, for example in soft drinks. A study led by the University of Southern California (USC) and involving researchers from Tübingen provides information about the effects of excessive consumption of artificial sweeteners such as sucralose on the brain. Although calorie-free, sucralose has an appetizing effect on the brain, especially in people with obesity. Researchers from the University Hospital of Tübingen, Helmholtz Munich and the German Center for Diabetes Research (DZD) were involved in the study.

Artificial sweeteners have been used in the food industry for over 130 years. The first sweetener, saccharin, was discovered in Germany in 1878. Sales of artificial sugar substitutes, most of which are calorie-free, have risen sharply, particularly in recent years. In Germany, one in two people take products with artificial sweeteners every day. The reasons cited include a diet- and calorie-conscious lifestyle. It is precisely this point that seems to become debatable by the new study results. As early as 2023, the World Health Organization recommended that artificial sweeteners should not be used as a substitute for sugar when it comes to weight loss.

Appetite and feeling of hunger increase

Sucralose leads to increased brain activity in the hypothalamus, an important control center of the brain. Among other things, this area of the brain is responsible for controlling food intake and the feeling of hunger. Sucralose activates precisely this area in the brain, which in turn is associated with a stronger evaluation of the feeling of hunger. “Artificial sweeteners, such as sucralose in our case, can influence appetite regulation in the brain to an extent that has a detrimental effect on weight,” explains Prof. Dr. Stephanie Kullmann from the Tübingen University Clinic for Diabetology, Endocrinology and Nephrology.

Artificial sweeteners cause confusion in the brain

The research team assumes that artificial sweeteners cause confusion in the brain by sending sweetness signals without providing the calories the brain needs. The hypothesis that the brain sends a signal to eat more when the promised calories do not arrive is already known from previous studies. The study involved 75 test subjects in the USA. They were asked to drink one of three drinks on three different dates: tap water, water sweetened with sucralose and water sweetened with sugar. Sucralose is around 600 times sweeter than conventional sugar. At each visit, the research team examined the participants’ fasting blood sugar levels, followed by a brain scan using functional magnetic resonance imaging (fMRI), which tracks blood flow to record activity in different regions of the brain. After the first scan, the test subjects drank one of the three drinks and were then examined again. In addition to the brain scans, blood samples were taken from the study participants after they had drunk the drinks and they were asked to assess their individual feelings of hunger.

Amazing results

Using the self-tests, the researchers were able to determine that sucralose increased the participants’ feeling of hunger by around 17 percent, particularly in test subjects who were abnormally obese. The research team was also able to demonstrate stronger connections to other parts of the brain that are responsible for controlling motivation. “Sucralose appears to impair the ability to make decisions,” says study leader Prof. Kathleen A. Page from the USC. “For example, we found increased brain activity between the hypothalamus and the anterior cingulate cortex, which controls the risks and benefits of a decision,” adds Prof. Kullmann. Another finding from the study: “The blood tests have shown that sucralose has no effect on the hormones that the brain uses to tell us when we had enough and are no longer hungry,” explains Prof. Kullmann.
 

Original-Publication:
Chakravartti, S.P., Jann, K., Veit, R. et al. Non-caloric sweetener effects on brain appetite regulation in individuals across varying body weights. Nat Metab 7, 574–585 (2025). DOI: https://doi.org/10.1038/s42255-025-01227-8

Scientific contact:
Prof. Dr. Stephanie Kullmann
Medical Clinic – Inner Medicine IV
University Hospital of Tübingen
Institute for Diabetes Research and Metabolic Diseases (IDM) of Helmholtz Munich at the University of Tübingen

Press contact:
University Hospital of Tübingen
Corporate Communications Department
Hoppe-Seyler-Straße 6, 72076 Tübingen
Tel. 07071 29-88548, Fax 07071 29-25024
presse(at)med.uni-tuebingen.de

Founded in 1805, Tübingen University Hospital is one of the leading centers of German university medicine. As one of the 33 university hospitals in Germany, it contributes to the successful combination of high-performance medicine, research and teaching. Well over 400,000 inpatients and outpatients from all over the world benefit annually from this combination of science and practice. The clinics, institutes and centers unite all specialists under one roof. The experts work together across disciplines and offer each patient the best possible treatment based on the latest research findings. Tübingen University Hospital conducts research for better diagnoses, therapies and healing chances; many new treatment methods are clinically tested and applied here. In addition to diabetology, neuroscience, oncology, immunology, infection research and vascular medicine are research priorities in Tübingen. The Department of Diabetology /Endocrinology has been the center of interdisciplinary research over the past 25 years, especially with the participation of surgery, radiology and laboratory medicine. This important discovery of the prediabetes subtypes was only possible due to the interdisciplinary collaboration between the hospital’s various departments. Tübingen University Hospital is a reliable partner in four of the six German Centers for Health Research initiated by the German Federal Government. www.medizin.uni-tuebingen.de

Helmholtz Munich is a leading biomedical research center. Its mission is to develop breakthrough solutions for better health in a rapidly changing world. Interdisciplinary research teams focus on environmentally triggered diseases, especially the therapy and prevention of diabetes, obesity, allergies and chronic lung diseases. With the power of artificial intelligence and bioengineering, the researchers accelerate the translation to patients. Helmholtz Munich has more than 2,500 employees and is headquartered in Munich/Neuherberg. It is a member of the Helmholtz Association, with more than 43,000 employees and 18 research centers the largest scientific organization in Germany. More about Helmholtz Munich (Helmholtz Zentrum München Deutsches Forschungszentrum für Gesundheit und Umwelt GmbH): www.helmholtz-munich.de/en    

The German Center for Diabetes Research (DZD) is a national association that brings together experts in the field of diabetes research and combines basic research, translational research, epidemiology and clinical applications. The aim is to develop novel strategies for personalized prevention and treatment of diabetes. Members are Helmholtz Munich – German Research Center for Environmental Health, the German Diabetes Center in Düsseldorf, the German Institute of Human Nutrition in Potsdam-Rehbrücke, the Paul Langerhans Institute Dresden of Helmholtz Munich at the University Medical Center Carl Gustav Carus of the TU Dresden and the Institute for Diabetes Research and Metabolic Diseases of Helmholtz Munich at the Eberhard-Karls-University of Tuebingen together with associated partners at the Universities in Heidelberg, Cologne, Leipzig, Lübeck and Munich. www.dzd-ev.de/en