What if weight management requires less attention to your scale and more attention to your alarm clock?
Research shows that a lack of sleep can sabotage efforts at weight management — and not just because your willpower takes a dive when you’re tired. Getting less than seven hours of sleep can lead to measurable changes in how, and when, you get hungry. Inadequate sleep can also impair your decision-making processes, causing increased calorie consumption and weight gain.
“Most of us don’t even realize how tired we are, even when we are clearly sleep-deprived,” said Michael Grandner, PhD., director of the Sleep and Health Research Program at the University of Arizona, during a 2025 Embody webinar titled “How Better Sleep Promotes Mental, Metabolic, and Cardiovascular Health.” “This is, at least in part, because being tired distorts our ability to assess how we’re feeling.”
Studies find that people who are getting five to six hours of sleep can describe themselves as well-rested, even when they’re doing poorly on performance tests, Grandner explained.
So, if you’re sleeping less than seven or eight hours each night, it’s important to rethink how (and why) you prioritize sleep. It may be one of the most important factors to adjust for sustained weight management, as well as your overall health. Here are the ways in which sleep loss can contribute to weight gain.
You crave calorie-dense foods.
“Nobody craves a salad at 2 o’clock in the morning, and there’s a reason for this,” Grandner said. Studies show that people who are tired are more likely to crave calorie-dense foods — those unhealthy snacks that are high in carbs, fats, and sugar.
In one study, researchers measured food preferences of subjects when they were well-rested compared with when they were sleep-deprived. When sleep-deprived, participants were more likely to prefer unhealthy foods, consuming an average of 600 more calories than when they were well-rested. ”The less sleep they got, the more likely they were to prefer unhealthy food,” Grandner said.
Subsequent brain imaging studies revealed possible mechanisms for this pattern, showing that sleep deprivation compromised the function of regions in the brain involved in reacting to food cues as well as making food choices.
You get hungry later at night.
When you’re sleep-deprived, it's not only what you want to eat that changes, but when you want to eat it. “A lack of sleep causes eating patterns to shift later,” Grandner said. “Which can lead to weight gain.”
One small study restricted people’s time in bed to five hours for five consecutive nights and then allowed them nine hours in bed for a five-night stretch. When sleep-deprived, they consumed 5% more calories than when well-rested. The researchers noticed a dramatic difference when they looked more closely at the breakdown of eating patterns. While members of the sleep-deprived group ate slightly less at breakfast and about the same as the well-rested group during the day, they consumed 42% more calories in after-dinner snacking.
Your decision-making is impaired.
A lack of sleep chips away at your ability to make good decisions, and this can affect choices you make around any type of healthy habit, including what you eat and drink, how you exercise, and even the sleep you get the next night.
One study that restricted the sleep of participants in a laboratory setting showed that decreased sleep caused an increase in attention lapses, the result of “microsleeps,” or very short periods of sleep-like brain activity. These lapses can affect different areas of cognitive function, including the choices you make.
However, just as poor sleep can contribute to weight gain, Grandner explained, getting enough sleep can help you, fairly quickly, build momentum toward healthy habits, including eating.
