Donut Daydreams

Researchers at University of California, Berkeley showed food images to 23 well-rested volunteers, and scanned their brains while they chose which ones looked more tempting. Then they kept the subjects awake all night, and tried it again. The result: lack of sleep made them want junk food.

As an incentive, the volunteers were promised the food they wanted most at the end of the experiment. After an all-nighter, the subjects overwhelmingly chose burgers, pizza and donuts over apples and carrots.

UC Berkeley professor of psychology and neuroscience Matthew Walker said the study, which was released in the journal Nature Communications this week, revealed that sleepy people had more brain activity in primitive donut-craving centers of the brain, while areas responsible for higher functions like calorie-counting were out to lunch.

"[The research] just adds further evidence to the notion that the single most effective thing we can do every day to reset our brain and body health is sleep," he said. "From a brain perspective, it certainly seems like the deck is stacked against us when we're sleep deprived in terms of making optimal choices."

According to the most recent figures from the Centers for Disease Control, more than 28 percent of adults sleep 6 hours or less per night. Among obese people, 61 percent get 6 hours or less.

Mounting Evidence

Past research has already shown a link between unhealthy food cravings and sleep loss, but this experiment reveals the underlying brain activity for the first time.

A study from Columbia University in New York last year showed that subjects had more activity in reward centers of the brain when they looked at high-calorie, fatty and sugary foods than when they viewed pictures of lighter fare. A study at the Stony Brook University School of Medicine on Long Island released earlier this summer found that out of 13,000 teens, 18 percent slept fewer than 7 hours per night. Out of those sleepy teens, 20 percent were more likely to eat fast food two or more times a week, and 25 percent less likely to have recently eaten fruit and veggies.

The American Academy of Pediatrics recommends that teens get between nine and 10 hours of sleep per night, and the Stanford Center for Sleep Sciences and Medicine says the average adult should get 8 hours and 10 minutes -- though there's lots of individual variation.

Researchers have also discovered that sleepy people burn more calories than their well-rested counterparts, but overcompensate by eating more than they use.

More Questions

Walker said his findings raise issues for further investigation. Subjects in the study had similar levels of health and body mass, but he said researchers need to look into how these effects play out over a range of body types.

"Are some people particularly vulnerable to the affects sleep deprivation, and are those the same people who are already most vulnerable to developing obesity themselves? I think we need to know that to develop good medical and public health policy."

Walker said researchers also need to integrate studies on the brain with those on physical effects of sleep deprivation, like hormonal changes and glucose levels in the blood.

Read More:

• Obesity And Sleep Deprivation Connection Revealed By UC Berkeley Study (Huffington Post)
• Lack of Sleep May Make Junk Food More Appealing (CBS)