People are more likely to indulge in unhealthy foods that are high in fat or sugar when they haven’t had enough sleep. In a recent study published in eLife, participants partook more heavily of an array of unhealthy foods including doughnut holes, chocolate chip cookies and potato chips following nights when they got only four hours of sleep than when allowed a full eight hours of sleep. 

Smell, not exhaustion, seems to be at the root of the increased snacking. Brain scans revealed that when someone is sleep-deprived, his/her piriform ­cortex, a region of the brain that processes odor, experiences a heightened ability to identify food smells…while its ability to communicate with the insula, a region that processes signals associated with food intake, is diminished. Net result: Tired people are more likely to succumb to the smell of high-calorie foods, such as doughnuts and potato chips—not just their mere presence. 

It’s possible (though not yet proven) that sleep-deprived brains intentionally steer people toward high-calorie foods when they’re fatigued as a survival strategy. For much of humankind’s history, packing on a few extra pounds during stressful times when sleep was in short supply was a prudent precaution. In the past, the problem that was costing ­someone sleep might make food hard to come by the next day. 

What to do: Try to avoid the smell of fatty or sugary foods following nights when you didn’t get sufficient sleep. If you can’t avoid those tasty smells, remind yourself that you are especially likely to be tempted by these foods when you are tired. This awareness can boost your ability to resist. If you’re trying to lose weight, include “get sufficient sleep” as part of your diet plan.