Is It Better to Sleep In or Exercise When You're Tired? Here's What New Research Says

Getting enough sleep ranks right up there with eating a balanced diet, moving your body and not smoking as some of the most crucial pieces of the wellness puzzle. But if we have to choose to sacrifice one of those for the other—say, ditch an hour of sleep to sneak in a sweat sesh after that movie kept us up too late last night—should we?

Scientists dove into this exact topic for a new study published in the June 2021 British Journal of Sports Medicine and the results are pretty eye-opening. After crunching the numbers from more than 380,000 middle-aged men and women enrolled in the UK Biobank research group, the study authors determined that higher levels of physical activity might be able to counteract the negative health impact of poor sleep.

The authors add that exercise and high-quality sleep definitely have synergistic effects on health (translation: your best bet is to prioritize both when you can), yet they summarize their findings in the paper: "Poor sleep was associated with a higher risk [of] all-cause and cause-specific mortality, and these risks were markedly exacerbated among participants with insufficient [exercise]."

The major finding of this research is that sleep and physical activity are intertwined, says Jessica Ball, M.S., RD, EatingWell's assistant nutrition digital editor.

"You need both pieces of the puzzle to feel and function at your best. If you are super-active but don't sleep, it could be hurting your health in the long run. Also skipping activity entirely led to worse health outcomes regardless of sleep. It's all about finding the balance of rest and activity that works with your life and that you can be consistent with," Ball explains.

Dating back to 2009, on average, the researchers gathered questionnaires, interviews and physical measurements from the participants through May 2020. They looked at their starting health condition, lifestyle habits and family history. Then, the authors summarized activity data using metabolic equivalent task minutes, which are related to how many calories different exercises generally burn.

Each participant's physical activity was categorized based on the World Health Organization (WHO) guidelines:

• High: 1,200 or more minutes per week, or 4 hours per day
• Medium: 600 to less than 1200 minutes per week, or 2 to 4 hours per day
• Low: 0 to less than 600 minutes per week, or less than 2 hours per day

Note that this includes any leisure time activity—including gardening, walking, strolling through the grocery store—not just formal "exercise," hence why the levels seem high. Plus, walking and yoga both clock in at 3 METs, which means they expend three times as much as sitting. A 10-minute mile, by comparison, is 10 METs. So that means five 30-minute walks plus two 30-minute runs at a 10-minute mile pace = 1,050 MET minutes; solidly in the medium category.

For sleep, they used five characteristics:

• The tendency to be a night owl over being an early bird
• Sleep duration
• The presence of insomnia
• Daytime sleepiness
• Snoring

Sleep score categories included: healthy (4 or higher), intermediate (2 to 3), and poor (0 to 1). (ICYMI, here are 4 ways to get a better night's sleep, according to an expert.)

By pairing sleep scores with activity scores, the participants were tracked until the conclusion of the study in May 2020 or until their death. Those with lower sleep scores had a higher risk for death from any cause, from cardiovascular disease and from stroke. The individuals with poor sleep and none or extremely limited activity had the highest risk of death.

These are the common traits among those who tended to be both more physically active and have a healthier sleep score:

• Young
• Female
• "Normal" body weight
• Eat more fruits and vegetables
• Spend less of their days sitting
• No reported mental health issues
• Never smoked
• Drank less alcohol

So does this mean we should sacrifice sleep to exercise? Not necessarily.

Making this a habit, "can lead to fatigue and more serious health consequences down the road. While staying active is a crucial part of a healthy lifestyle, try getting the extra rest and working in movement throughout your day. Adequate sleep is crucial for exercise recovery, too, so you can't have one without the other," Ball says.

The results of this study also show that any level of physical activity at or above the lower threshold recommended by the WHO appeared to eliminate most of the detrimental impacts of poor sleep and mortality.

"As with anything, choosing whether to wake up and exercise or sleep in varies based on every individual situation—there is no right or wrong answer," Ball adds. "That said, if you are consistently sacrificing sleep for morning workouts, it could be worth trying to restructure your routine to workout at another point in the day. Exercise won't be as beneficial for your body if you have racked up a significant 'sleep debt.'"

On a day when you could use to catch up on a few more zzz's, Ball recommends sprinkling in shorter movement breaks throughout the day, like with a walk around the block every couple hours or 10 minutes of yoga flows in the morning and before bed.

"Even if you're short on time, you can usually find 5 to 10 minutes here and there to get up and move. Plus, it'll help you feel more energized throughout the day," Ball says.

Up next: Yes, you can exercise when you have literally zero time—here's how.