You’ve stayed up late, either answering emails or binge-watching a series, and the next morning you feel groggy and irritable. Sweet pastries or a greasy sandwich for breakfast seem far more appealing than your usual yogurt and berries. By midday, you find yourself munching on chips or candy in the office break room. It’s not that you suddenly lack willpower; it’s just that a sleep-deprived brain pushes you toward high-calorie snacks.
According to Joanna Fong-Isariyawongse, an assistant professor of neurology at the University of Pittsburgh, there’s a reason this cycle repeats so predictably. Lack of sleep signals hunger, weakens self-control, impairs glucose metabolism, and increases the risk of weight gain.
These changes can occur even after just one night of poor sleep, and if not addressed, they can become very dangerous over time.
Sleep deprivation is a problem for millions of people around the globe. According to the Centers for Disease Control and Prevention (CDC), more than one-third of adults in the U.S. regularly sleep less than seven hours a night. Nearly three-quarters of teenagers fail to get the recommended 8-10 hours during the school week.
A disrupted internal clock due to lack of sleep leads to increased cravings and raises the risk of obesity and metabolic diseases.
How Sleep Deprivation Affects Hunger Hormones
The body regulates feelings of hunger through hormonal feedback, involving two key hormones. The first, ghrelin, produced in the stomach, signals hunger. The second, leptin, produced in fat cells, tells the brain that you’re full. Even one night of limited sleep increases ghrelin levels and decreases leptin levels. The result? Heightened feelings of hunger and reduced satisfaction from food, as reported by Science Alert.
The brain becomes less responsive to signals of fullness while simultaneously increasing levels of stress hormones that can amplify appetite, noted Joanna Fong-Isariyawongse.
In a recent study, healthy adult participants reported increased hunger and cravings for calorie-dense foods after just four to five hours of sleep. This effect intensifies with regular sleep deprivation, potentially leading to chronically elevated appetite.
Why the Brain Switches to Reward Mode
Lack of sleep alters how the brain evaluates food. Research has shown that after just one night of sleep deprivation, activity in the prefrontal cortex—responsible for decision-making and impulse control—decreases.
At the same time, areas of the brain associated with reward, such as the amygdala and the nucleus accumbens, become more responsive to appealing food cues.
In simple terms, the brain becomes more easily tempted by unhealthy food and less capable of resisting it.
Slowed Metabolism Leads to Increased Fat Storage
Ms. Fong-Isariyawongse pointed out that sleep is also crucial for regulating blood sugar levels. When the body is well-rested, it effectively uses insulin to move sugar from the bloodstream into cells for energy. However, even one night of poor sleep can reduce insulin sensitivity by 25 percent, leaving more sugar in the blood.
If the body cannot efficiently process sugar, it is more likely to convert it into fat. This contributes to fat accumulation, particularly in the abdominal area. Over time, poor sleep increases the risk of developing type 2 diabetes and metabolic syndrome—a cluster of health issues that can lead to heart disease and diabetes.
Moreover, sleep deprivation raises cortisol levels, the primary stress hormone. Elevated cortisol levels promote fat storage and further disrupt appetite regulation.
In a modern culture that embraces nightlife and wakefulness, sleep is often seen as optional. However, our bodies disagree. Sleep is an active, essential form of restoration.
But there’s good news: just one or two nights of quality sleep can reverse the damage caused by previous sleep deprivation and restore the body’s natural balance.
So, the next time you crave junk food after a night of poor sleep, remember that your biology is not letting you down. It’s responding to stress and fatigue. The most effective way to restore balance is to get a good night’s sleep, says Ms. Fong-Isariyawongse. After all, sleep is the most powerful tool for appetite control, energy regulation, and overall health.