Hunger makes all sweetness more rewarding, but artificial sweetener users show unique brain responses

A recent study published in the journal Food Quality and Safety suggests that feeling hungry amplifies our immediate enjoyment of sweet tastes, regardless of whether the sweetness comes from sugar or zero-calorie substitutes. The research also provides evidence that people who regularly consume artificial sweeteners show heightened brain activity in areas linked to self-control when tasting sweet drinks. These findings imply that switching to zero-calorie options might subtly change how the brain processes sweet temptations over time.

Excessive sugar consumption plays a major role in the development of obesity, type-2 diabetes, and cardiovascular disease. To reduce calorie intake, many people have turned to non-nutritive sweeteners, which are artificial or plant-derived additives that taste sweet but provide little to no metabolic energy. The widespread use of these low-calorie alternatives has raised questions about how they might affect human biology.

Some scientists propose that consuming sweetness without the accompanying calories might disrupt the body’s natural energy signaling. This disruption could potentially alter a person’s taste preferences and change how the brain’s reward system responds to food.

Past long-term trials have yielded mixed results regarding these potential changes. Some reports suggest that using artificial sweeteners alters a person’s preference for sweet foods, while other reports find no noticeable difference. A factor that might explain these mixed results is the physical state of the body, specifically whether a person is hungry or full.

Hunger naturally heightens the biological drive for energy, which tends to make calorie-dense foods more appealing. Satiety, or the feeling of being full after a meal, suppresses the natural urge to seek out food. Because physiological states heavily influence eating behavior, evaluating these factors together provides a better picture of how dietary habits shape human food preferences.

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The research team included scientists from Jiangnan University in China and the University of Oxford in the United Kingdom. They aimed to understand how metabolic states and habitual sweetener use combine to influence sweet preferences at both conscious and subconscious levels.

To explore these dynamics, the researchers recruited 30 participants between the ages of 19 and 27. The sample was divided into two equal groups of 15 based on their regular dietary habits. One group consisted of habitual sugar consumers who regularly drank sugar-sweetened beverages but rarely used zero-calorie sweeteners. The second group consisted of habitual non-nutritive sweetener consumers who regularly drank zero-calorie options but rarely consumed regular sugar.

The experimental procedure required each participant to attend two separate testing sessions. One session took place when the participants were hungry, meaning they had fasted for at least three and a half hours. The other session took place when they were satiated, occurring within an hour after they had eaten a full meal.

During each session, the participants tasted three different sweet solutions presented in small, ten-milliliter portions. The three drinks included a full-sugar solution, a half-sugar solution mixed with zero-calorie sweeteners, and a zero-sugar solution containing only zero-calorie sweeteners. The researchers matched all three solutions to have the exact same level of sweetness, ensuring that the participants could not consciously tell them apart based on taste intensity alone.

The testing involved both explicit and implicit measurements to capture a complete picture of the participants’ reactions. For the explicit measures, the participants rated their liking of the drinks on a nine-point scale. They also completed questionnaires designed to assess their emotional responses, rating basic feelings such as arousal and pleasantness. Another questionnaire provided twenty-five specific emotional words, allowing the participants to build a detailed emotional profile for each drink.

For the implicit measures, the scientists monitored the participants’ bodies and brains to record automatic biological reactions. They used an electrocardiogram, which is a medical device that records the electrical signals of the heart, to measure heart rate and nervous system activity. They also used functional near-infrared spectroscopy, a non-invasive brain imaging technique that uses light to monitor blood flow and oxygen levels in the brain.

The data provides evidence that hunger significantly increased how much the participants liked all the sweet drinks. The participants consistently gave higher ratings to the drinks when they were hungry compared to when they were full. This increase in enjoyment happened regardless of whether the drink contained full sugar, half sugar, or no sugar at all.

This specific finding suggests that the physical state of hunger makes the sensory experience of sweetness itself more appealing. The body does not seem to selectively favor the caloric content of the sugar during the immediate moment of tasting. The craving for energy tends to turn up the volume on the sweet taste, making any sweet sensation highly rewarding in the short term.

The electrocardiogram data matched these conscious ratings by showing physical signs of arousal during the hungry state. When hungry, the participants experienced shorter intervals between heartbeats and an overall increased heart rate while tasting the drinks. These changes indicate an activation of the sympathetic nervous system, which is the physiological network that drives the body’s active, alert responses.

The brain imaging results revealed a distinct difference between the two consumer groups. Habitual consumers of zero-calorie sweeteners showed significantly stronger oxygenated blood flow in the left dorsolateral prefrontal cortex compared to the sugar consumers. This specific area of the brain is highly involved in cognitive control, dietary self-regulation, and the ability to resist temptations.

This increased brain activity happened even though the participants did not know which type of sweetener they were tasting. The two groups also reported identical levels of conscious enjoyment and emotional response. The findings suggest that long-term use of zero-calorie sweeteners might train the brain to engage more self-control and monitoring networks whenever sweet tastes are encountered.

These results offer practical guidance for public health initiatives and the food industry. Because hunger enhances the appeal of any sweet taste, replacing sugar with artificial sweeteners in snacks might satisfy cravings without adding extra calories. Developing products to be less sweet overall, while ensuring they remain pleasurable, might be a highly effective long-term strategy for reducing sugar intake.

The authors noted some limitations in their experimental design that provide context for these conclusions. The study relied on a relatively small sample size, which limits the ability to generalize the findings to larger populations. Some participant data had to be excluded from the brain imaging analysis due to poor signal quality caused by hair obstruction, which reduced the sample size for that specific measure. The emotion analysis also involved a small sample, meaning those specific results should be interpreted with caution.

The participant group contained significantly more females than males. This imbalance means the results might not capture potential physiological differences in how men and women process food rewards. Future research projects would benefit from using larger participant groups with an equal representation of both sexes.

Another limitation involves the use of self-reported questionnaires to determine the participants’ dietary habits. Self-reporting is often subject to memory biases, meaning people might not accurately recall exactly how much sugar or artificial sweetener they consume. Future studies could use long-term dietary logs or medical biomarkers to track nutrient intake more accurately.

The testing environment also lacked the context of real-world food choices. The participants drank plain solutions from transparent cups, which removes the influence of food packaging, branding, and nutritional labels. In everyday life, knowing that a drink is zero-calorie can strongly influence a person’s expectations and eating behaviors.

Future research could measure actual food consumption after the tasting sessions to see if these brain patterns affect how much people eat later in the day. Investigating these factors in more natural eating environments will help explain how artificial sweeteners fit into long-term dietary health.

The study, “An exploratory study of sweetness preference for habitual sugar and non-nutritive sweetener consumers revealed by explicit and implicit measures,” was authored by Jiaona Jiang, Fang Zhong, Feifei Xu, Yixun Xia, and Charles Spence.