I go to the gym every morning, even if I get to bed late, which happens about twice a week. On those days, which is healthier: getting maybe six hours of sleep and working out, or getting seven to eight hours of sleep and missing my workout?
If it’s just twice a week on nonconsecutive nights and you can catch up on sleep during subsequent nights, it’s probably fine to stick with your early workout, says Harly Greenberg, medical director of the North Shore-LIJ Sleep Disorders Center.
Getting just six hours of sleep occasionally is common, and there’s no data showing any negative consequences from doing this a couple of times a week if you make up the sleep later.
If it starts happening more frequently, however, then it can have a negative impact. Being partially sleep-deprived — or sleeping one to two hours less than you really need three or more times a week — can have significant effects on your metabolism, promoting weight gain and decreasing your ability to lose weight.
There are a lot of factors that combine to cause these effects. For one, insufficient sleep can interfere with the function of hormones that regulate hunger and satiety, like grehlin and leptin. It also decreases the ability of glucose to metabolize insulin, which can lead to weight gain. Sleep-deprived people are more sedentary and crave energy-dense foods. Finally, being awake for more hours during the day simply gives you more time to eat. These are a few reasons why getting too little sleep has been associated with increasing rates of obesity.
So if you’re working out to lose weight or help keep weight off, you’ll be counteracting those efforts if you continually cut your sleep time short in order to exercise. At a certain point, you’d be undoing your hard work. And, of course, aside from weight issues, partial sleep-deprivation will have a cumulative negative effect on your performance throughout the day. You’ll be slower to perceive and react to the circumstances around you. The sleep-deprived often fail to recognize their deficits in performance, so you may not even be aware of this.
It’s important to remember that sleep needs vary by individual. Just like there are short and tall people, there are people who only need six hours of nightly sleep and others who need eleven hours. Don’t just assume that getting eight hours is best for you; you may really need less or more than that. So consider how much sleep you personally need to feel your best and perform optimally when you’re deciding whether to head for the gym or grab an extra hour in bed.