Lack of Sleep Increases Cravings for Sweets: How Sleep Affects Appetite.

According to ТСН: Lack of sleep not only worsens mood but also alters the brain's perception of smells, which, in turn, can affect appetite. Short sleep activates neural mechanisms similar to those that respond to cannabis, making sweet and fatty foods more appealing.

A study led by Thorsten Kant from the Feinberg School of Medicine aims to examine how sleep deprivation affects the olfactory system and food choices. The experiment involved 25 healthy adults who alternated between sleeping for 4 hours or a full 8 hours. Participants showed an increased level of 2-oleoylglycerol in their blood after a short night—this molecule activates endocannabinoid receptors.

During short nights, participants did not feel a significant difference in hunger; however, their food choices changed: under-slept individuals consistently chose more caloric foods, for instance, preferring sweet donuts over muffins.

In the second phase of the experiment, participants underwent MRI scans while inhaling various food odors. Those who had slept less showed a greater reaction in the part of the brain responsible for processing smells, but this was not enough to clearly explain their food preferences.

Scientists established that the connection between the piriform cortex and the insular lobe—a regulator of eating behavior—was significantly weaker in people with elevated levels of 2-oleoylglycerol. This reduction in information flow may explain why the brain craves high-calorie foods after short sleep.

Neurobiologist Christian Benedict believes that the study's results are quite promising but emphasizes that factors other than sleep duration, such as wake-up time, may also influence outcomes.

Kant's team plans to continue the research to determine how olfaction changes throughout the day and how it affects eating behavior. One of the projects will be dedicated to studying the impact of prolonged fasting intervals on circadian rhythms and the brain's response to smells.

Scientists believe that a better understanding of these mechanisms could open new ways to improve eating behaviors and treat obesity, as it turns out that olfaction is more important for appetite control than previously thought.

Studying the Impact of Sleep Deprivation on Appetite

In 2017, a research team led by Erika Deiza conducted a pilot randomized study on a healthy individual without diabetes. The participant used a fitness tracker and glucose monitor, and also filled out mood and food craving questionnaires several times a day. On certain nights, her sleep was artificially restricted to four hours, while she sometimes slept at least six hours.

Initial analysis found no significant increase in the average blood glucose level after nights of sleep deprivation. However, further analysis showed that after short sleep, there was greater variability in blood glucose levels—measurements fluctuated throughout the day, not remaining within stable ranges. This indicates that not so much the overall glucose level was high, but rather the sharp changes.

Another important aspect concerned eating behavior: after nights of insufficient sleep, the participant more frequently craved higher-calorie products. Researchers concluded that sleeplessness increases the likelihood of 'food cravings' the next day, even in people without diabetes.

Additionally, the participant's emotional state was evaluated using the PANAS scale. There were no significant changes in positive emotions, but sleep deprivation led to an increase in negative emotions.

Scientists emphasize that this pilot study has a very small sample size, so its results cannot be unconditionally generalized to other cases. However, it does indicate an important trend: even one short night without sleep can lead to increased food cravings and a deterioration in emotional state in healthy individuals.