Katherine Dudley, MD, MPH

Researchers measuring activity levels found that people who tend to go to bed later and sleep later also tend to get less physical activity, compared to early risers. However, these results don’t mean that being a night owl is the cause of getting less activity, or that such behavior can’t be changed.

Many people now wear smartwatches and other wrist-based devices, and use them to collect and track information about their sleep. But the algorithms that govern how the devices work are opaque, and there is no data comparing them to devices that sleep researchers use.

Trying to make up for not getting enough sleep during the week by sleeping longer on weekends has been found to have negative effects such as weight gain, expending less energy, and increased calorie intake during evenings.