Does sleep affect how many calories you burn?

Yes, though not the way you’d hope. A short night burns slightly more, because you’re awake longer. The catch is that people eat more than the extra burn. In a lab study, five short nights raised daily burn by about 5% and still led to almost 2 pounds of weight gain. Sleep matters for your weight because it steers what you eat.

Sleeping is about as low as your burn goes: the Compendium of Physical Activities rates it at 1.0 MET, the same as lying quietly. So it seems like less sleep should mean more burn and more loss. The first half is true.

The simple version

Staying up late is like leaving the lights on longer. The bill goes up a little. Then there’s the trip to the fridge, which costs far more.

The studies

• Burn and eating. In 2013, 16 adults lived in a sleep lab for about two weeks. On five nights of short sleep they burned about 5% more a day, ate more than that, mostly after dinner, and gained about 1.8 pounds. Back on normal sleep, they ate less.
• Dieting. In 2010, 10 adults dieted for two weeks twice, once with 8.5 hours in bed each night and once with 5.5. With short sleep they lost 55% less fat (1.3 pounds against 3.1) and 60% more lean mass. Same diet, worse result.

What to do

• Protect your sleep, most of all while you’re cutting calories.
• On short nights, plan your evening food ahead, since that’s when the extra eating happened.
• If you track sleep, look at it next to your weight trend. A run of short nights can explain a stalled week.