Popular sweetener sucralose may intensify hunger signals and contribute to weight gain, new study suggests

With over 20% of adults in the United States living with obesity, there is significant interest in foods and beverages that can help manage weight. Among the most commonly used tools in calorie reduction are non-caloric sweeteners, which are often marketed as effective aids in weight control. However, a new study raises concerns that one such sweetener—sucralose—may, in fact, increase hunger and contribute to overeating.

The research, conducted by scientists at the Diabetes and Obesity Research Institute at the University of Southern California, examined how sucralose influences brain activity related to hunger. Using functional magnetic resonance imaging (fMRI), the researchers observed how the brain’s hypothalamus—a key region involved in appetite regulation—responded after consumption of drinks sweetened with sucralose, sucrose (table sugar), or plain water.

The study’s findings, published in Nature Metabolism, suggest that sucralose may significantly increase hunger-related brain signals compared to both sugar and water, a response that could lead to heightened appetite and greater food consumption.

Understanding Sucralose and Its Impact on the Brain

Sucralose is an artificial sweetener known for its high sweetness potency—estimated to be between 385 and 650 times sweeter than sucrose by weight. Despite its popularity as a sugar substitute, the long-term effects of sucralose on appetite and metabolism are still being explored.

To investigate further, researchers recruited 75 adults aged 18 to 35, representing three different weight categories: healthy weight, overweight, and obesity. Each participant took part in three separate experimental sessions, during which they consumed either a sucralose-sweetened drink, a sucrose-sweetened drink, or water. Brain scans were taken before the drink and at intervals of 10, 35, and 120 minutes afterward. Participants also provided self-reported hunger ratings during each session.

The hypothalamus, the brain region of focus in this study, plays a critical role in maintaining various physiological functions, including temperature regulation, hormone production, and hunger signalling. Increased blood flow in the hypothalamus is associated with stronger hunger signals.

Sucralose Heightens Hunger Signals, Especially in Some Groups

The analysis revealed that sucralose increased hypothalamic blood flow more than both water and sucrose, indicating a heightened hunger-related brain response. This finding was consistent across the overall participant group but varied when broken down by weight category and sex.

• People at healthy weights showed a greater increase in hypothalamic activity after consuming sucralose compared to sucrose.
• People with overweight did not exhibit significant differences in hypothalamic blood flow across the three beverages.
• People living with obesity experienced increased hunger-related brain activity after consuming sucralose compared to water—but not when compared to sucrose.

These results suggest that while sucralose may not affect everyone equally, it can still trigger hunger signals in a substantial portion of the population.

Further differences emerged when sex was considered:

• Female participants displayed a more pronounced brain response to sucralose in comparison to both sugar and water. The researchers suggest this supports previous findings that women may have a stronger neurological reaction to food-related cues.

Additionally, the researchers found that sucralose significantly increased functional connectivity between the hypothalamus and the anterior cingulate cortex, a brain region involved in reward processing. This enhanced coupling may further intensify food cravings and undermine weight control efforts.

Hunger Ratings Support Brain Imaging Findings

Self-reported hunger levels added further support to the brain imaging data. Participants began each session with similar hunger levels regardless of the drink they were about to consume. However, following drink consumption, those who had consumed the sucralose-sweetened beverage reported higher hunger compared to when they had consumed the sucrose-sweetened drink. Interestingly, sucralose did not produce a greater hunger response than water in these subjective ratings.

The researchers hypothesise that this might be due to the body’s hormonal response. Sucralose may fail to activate the same satiety-related hormones that are typically released in response to calorie-containing foods or beverages, potentially leading to a mismatch between perceived sweetness and physiological satiation.

While more studies are needed to confirm the hormonal mechanisms, these results suggest that sucralose could inadvertently stimulate appetite, counteracting its intended use as a calorie-free sugar alternative for weight loss.

Clinical Perspectives on the Findings

The potential implications of this study extend into clinical practice. Dr Mir Ali, a board-certified general surgeon and bariatric specialist, as well as the medical director of MemorialCare Surgical Weight Loss Center, discussed the findings with Medical News Today.

“Based on this study, it seems that the brain processes non-caloric sweeteners to the same or greater extent than actual sugar,” said Dr Ali.

He suggested that this might influence how clinicians advise their patients:

“We already recommend that our patients emphasise protein and non-starchy vegetables in the diet and minimise carbohydrates and sugars,” Dr Ali noted. “After this study, I’m also inclined to recommend my patients minimise non-caloric sweeteners as well.”

Registered dietitian Eliza Whitaker, MS, RDN, founder of Nourished Nutrition and Fitness, also shared her insights with Medical News Today:

“This could suggest that the brain expects energy from calories when eating something sweet. However, this expectation is not met when consuming non-caloric sweeteners, like sucralose, which may prevent the processes within the hypothalamus that reduce appetite after eating something sweet from occurring the way they do when consuming calorie-containing sweeteners.”

Whitaker noted that the current evidence would not prompt a change in her clinical recommendations yet, but acknowledged the need for individualised consideration:

“It may be beneficial to assess sucralose intake for someone who has made other dietary adjustments and feels they are still unable to reach their health goals,” she commented.

Final Thoughts

This study provides compelling evidence that sucralose, a widely used non-caloric sweetener, may not function as neutrally in the body as once assumed. Instead of helping people feel satisfied while avoiding calories, it may actually intensify hunger signals and lead to greater food intake—especially among people with healthy weights and women.

While further research is necessary to clarify the long-term effects and hormonal mechanisms involved, the findings offer a cautionary note for individuals and clinicians who rely on non-caloric sweeteners as part of a weight management strategy. As the scientific community continues to investigate how artificial sweeteners interact with human metabolism and brain function, personalised and evidence-informed dietary guidance remains essential.

CCH Insight:

The instinctive reaction to this might be “there’s no point in consuming sucralose because it stimulates appetite”. However, if consuming sucralose means you avoid eating/drinking refined sucrose, and then you eat something healthy and nutritious when the sucralose stimulates your appetite, this is undoubtedly a benefit, even if calorie intake is not reduced. Further research is needed to determine how people respond in real life to the increased appetite stimulated by sucralose.