I feel great on 7 hours of sleep but like a zombie after 8 — two doctors explain why, and how much sleep is enough

We’ve long been told that eight hours of sleep is the golden rule. Whether it’s boosting your physical recovery or keeping your mental health in tip-top condition, eight hours of sleep has historically been cited as a good benchmark to aim for.

But how true, and realistic, is that rule? With our busy schedules and hectic lifestyles, squeezing in eight hours of sleep isn’t always possible, especially for mothers, shift workers and carers.

And personally, I’ve realized my mornings are a lot brighter since I’ve started sleeping for only seven hours a night. So, as part of our Sleep Awarness Week coverage, I’ve spoken to the experts to find out whether seven hours of sleep is really enough and why I'm feeling better than ever after less sleep.

Is 7 hours of sleep enough?

The short answer is yes, seven hours of sleep is enough. “The National Health Service (NHS) recommends that the average adult needs seven to nine hours of sleep every night,” says Dr. Hana Patel, the Resident Sleep Expert for Time4Sleep.

This is generally considered an adequate length of time for us to cycle through each essential stage of sleep enough times.

This includes sufficient time spent in light sleep, REM sleep and deep sleep to ensure proper mental and physical recovery. We usually experience around five to seven sleep cycles a night. So sleeping for under seven hours risks not getting enough sleep cycles.

“The American Academy of Sleep Medicine and the Sleep Research Society recommend at least 7 hours per night for adults to maintain health,” says Dr. Julio Baute, a medical doctor and wellness consultant, agreeing with Patel.

“Routinely sleeping less increases risks for weight gain, diabetes, hypertension, and heart disease,” he adds.

However, it’s important to note that it differs from person to person. The amount of sleep you need depends on your age, health conditions and gender.

Some people will naturally sleep for longer than others; it all depends on whether you feel awake enough after seven hours of sleep.

Why do I feel most energized after 7 hours of sleep but tired after 8?

I’ve always been someone who swears I need nine hours of sleep a night, and sometimes even a nap during the day. It was excessive, and it gave me a lot of nighttime anxiety.

I’d stare at the clock telling myself I wouldn’t be able to get my precious nine hours of sleep.

So recently, I’ve tried something different. I’ve been setting my alarm for 7.5 hours after I go to bed. Which means I usually get anywhere from 7-7.5 hours of sleep a night.

Since starting this experiment, I’ve been waking up with more energy and a better mood.

I expected to crash halfway through the day, exhausted from my ‘lack’ of sleep. But nope. I was wrong. Sure enough, I avoided any energy dips in the afternoon and felt more switched on than after my usual nine hours of sleep.

But why did I feel better after less sleep?

I wasn’t interrupting a sleep cycle

Dr Lindsay Browning, a neuroscientist and renowned sleep expert, explains that “If you’re woken up from the deepest part of sleep, so the middle of a deep sleep cycle, you’ll feel really groggy.” This is called sleep inertia.

This is because “your body wants you to finish the full sleep cycle,” the doctor adds.

Each sleep cycle lasts roughly 1.5 hours. So, if you wake up after 7.5 hours of sleep, it’s more likely you’re waking up at the end of a cycle, during light sleep. However, waking up after eight or 8.5 hours of sleep means you’re more likely to be in deep sleep.

This explains why I was waking up feeling a lot more energized after 7.5 hours of sleep compared to 8.5.

I was keeping a regular sleep schedule

Setting myself an alarm exactly 7.5 hours after I went to sleep every night meant I was keeping a very consistent sleep schedule. I was naturally sleepy in the evenings, meaning I fell asleep fast every night, making it easy to go to sleep early and wake up early.

Keeping a consistent sleep schedule is essential to keep our circadian rhythm — our internal body clock — working well. This is the rhythm that determines when we feel sleepy and awake, and controls our sleep hormones.

Going to bed and waking up at the same time every day will regulate the release of these hormones, including melatonin in the evenings to help you sleep and cortisol in the mornings to wake you up.

In fact, recent studies have even found that sleep regularity can be more important than duration when predicting mortality risk.

I wasn’t oversleeping

Sleeping nine hours (or more) a night and sometimes napping meant I was actually oversleeping — and this can be as bad as undersleeping.

“It's important to note that oversleeping often worsens the overall sense of fatigue and can contribute to feelings of sluggishness or even a persistent lack of energy,” explains Dr. Leah Kaylor, a clinical psychologist who specialises in sleep.

Turns out, I didn’t need nearly as much sleep as I initially thought. Who knew seven hours could actually be better for you than nine hours of sleep?

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