Do you sleep 8 hours daily and still feel tired? Scientist explains how it will keep happening if you miss this 1 thingUpdated on: Aug 28, 2026, 09:28:35 IST

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Sleep irregularity, caused by weekend schedule shifts, can lead to fatigue, even with sufficient eight hours of sleep, Dr Andy Galpin explains.

Think you’re doing everything right for your sleep, but still feel exhausted? The reason might be just as simple as sleep regularity. In an August 28 podcast clip shared by Dr Mark Hyman on Instagram, Dr Andy Galpin, PhD, an elite performance coach and scientist, explained why people who sleep 8 hours every day still feel tired when they wake up.

Why do you still feel tired after sleeping 8 hours?

In the clip, Dr Hyman asked Andy to explain the problems most people have with sleep and their causes. According to him, the biggest problem people face with sleep is that they don't pay attention to the outside of total sleep: sleep regularity – going to bed and waking up at the same time each day.

He explained, “They'll say, hey, I got my eight and a half hours or seven and a half [of sleep]. But we had social jet lag. Social jet lag is the idea that you basically give yourself jet lag on the weekends. Not because you sleep less, but because you sleep in a two or three-hour different time domain.”

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A post shared by Mark Hyman, M.D. (@drmarkhyman)

What is sleep jet lag?

Andy explains that one can give themselves sleep jet lag by changing the time they usually sleep on weekends. Here's how: “Let's say you go to bed at 10 on the weekdays, wake up at 6, there's your eight hours. But then on the weekends, you stay up until 2 am and sleep until 10. You still got your eight, but you've given yourself jet lag because you're now four hours off.”

Many of us do that because we are out socialising or just trying to relax our minds on the weekend. But this is where your body suffers from sleep irregularity. “It might not be about how much sleep you’re getting. It’s about when you’re getting it. Even if you get 8 hours a night, shifting your sleep schedule on the weekends (what researchers call social jet lag) can leave you feeling wired, foggy, and under-recovered,” he added.

Who suffers the most?

According to Andy, most people focus on sleep quantity. But sleep regularity has a much bigger impact on how you feel than the number of hours alone. And the older you get, the harder it is to bounce back.

He explained that 20-year-olds, and even early 30-year-olds, can get away with sleep jet lag. However, for people who are past that age, it becomes really debilitating, even if they sleep eight and a half hours every day. They will still feel exhausted if there is no regularity.

Andy explained, “Sleep regularity is more important than people think, meaning going to bed and waking up at the same time every day. When it comes to perceived feeling and your energy levels, that regularity will have a bigger impact than the total hours.”

Dr Andy Galpin, PhD, has spent the last 20 years focused on the science and practice of enhancing Human Performance, in all its forms. Academically, he is a scientist and tenured professor with a PhD in Human Bioenergetics and an MS in Human Movement Sciences. He has spent 13 years running the Biochemistry & Molecular Exercise Physiology Lab and the Centre for Sport Performance

Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. Always seek the advice of your doctor with any questions about a medical condition.

This report is based on user-generated content from social media. .com has not independently verified the claims and does not endorse them.

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