In 1999, a team in Basel went looking for the body's best sign that someone was about to fall asleep quickly.
The winner was the hands and feet. More exactly, how far the blood vessels in the skin of the hands and feet opened up and let heat out. The wider they opened, the faster sleep came. Sleep, it seems, starts at the toes.
It is a small finding with a big idea behind it. Falling asleep is not only about switching off the mind. It is about the body clock running its evening routine, and part of that routine is shedding heat through the hands and feet.
That is the thread through the tips sold to reset your body clock. Some of them work with the body clock and have a finding behind them. Others are folklore with a good story. Here is which is which.
The clock
Our body clock runs a little long. 7 Ways to Make Every Day Work Better, linked below, has the man who went looking: in 1962, Michel Siffre spent two months 130 metres underground with no way of telling the time. Kept away from clocks and daylight, people settle into a day of about 24 hours and 11 minutes. Left to ourselves, we would all be a little late. Daylight pulls the clock back into line each morning.
Some clocks run later than others, and teenagers' run latest of all. When Seattle moved its secondary-school start time nearly an hour later, students slept a median 34 minutes more, their grades rose 4.5%, and attendance improved. They had not stopped being lazy. Their mornings had stopped fighting their clocks. Teenagers everywhere, vindicated.
Regular hours matter as much as early ones. For 30 days, 61 university students kept sleep diaries. In the most irregular sleepers, melatonin, the body's evening signal of night, started about two and a half hours later than in the most regular ones, and the more regular a student's sleep, the better their grades. A model of their light exposure put most of the difference down to light: the irregular sleepers got a weaker daily pattern of bright and dark.
Why You're Still Exhausted Despite Doing Everything Right has the bigger picture. Sleeping in at the weekend is like flying across time zones twice a week without leaving the house. And among 60,977 adults who wore a motion sensor for a week, the most regular sleepers were 20 to 48% less likely to die over the following years than the least regular. Regularity predicted it better than hours of sleep did. That is a link, not proof, but it points the same way.
The clock does far more than make us sleepy. It times hormones, digestion, body temperature and mood. And modern life keeps nudging it later. How to Boost Energy Levels Naturally: Little-Known Remedies That Actually Work has the people who read on a lit screen before bed: they took longer to fall asleep, made less melatonin, the hormone of darkness, and were less alert the next morning than when they read a printed book.
So the hacks that work tend to do one of two things. They give the clock a clearer signal of day and night, or they help the body do the cooling it already wants to do at bedtime.
Morning light, no sunglasses
Light is the clock's strongest signal, and morning light sets it earliest.
How to Quit Coffee: Getting Through Caffeine Withdrawal puts it plainly: get outside in the first part of the day, even under cloud, without sunglasses and not through a window. 7 Ways to Make Every Day Work Better has why the outdoors wins: a clear day gives 10,000 lux or more, even out of direct sun, an overcast day about 1,000, and an office only 320 to 500.
It does not take long to reset, either. After a summer weekend camping with nothing but natural light, people's body clocks moved earlier by about 69% of what a full week of camping had done. Winter light does its own work: under winter's natural light alone, the biological night began earlier and lasted longer than under electric light.
Indoors, a window helps. How to Boost Energy Levels Naturally, linked above, has the 49 office workers: those with no window near them slept worse, and those with windows got more light across the working week and slept longer.
One popular tip needs correcting, though. Daylight on open eyes is the point. Looking towards the sun is not. Face away from it, look at the sky and the world around you, and let the light do its work.
Warm feet
The Basel finding has a practical cousin.
In 2018, six young men slept for seven hours in a cool room, once with bed socks on and once without. With the socks, they fell asleep 7.5 minutes faster, slept 32 minutes longer, woke up 7.5 times less often, and spent 7.6% more of the night actually asleep. Their feet stayed warmer, and the difference between the skin of their feet and the skin of their trunk grew, just as the Basel finding would suggest.
Six people is a tiny test. But a pair of warm socks costs almost nothing, and it works with the body's own plan rather than against it. Grandma was right about the socks. A hot water bottle at the feet works on the same idea.
A cool head
If warm feet help, what about a cool head?
The popular tip is an ice pack on the back of the neck before bed. Nobody has tested that. Something close has been tried, though. In 2021, 24 veterans with long-standing insomnia used a device that cooled the forehead every night for four weeks. Seventeen of them, 71%, improved markedly, and ten reached the normal range. There was no comparison group, so some of that may be the effect of trying something new. It is a promising first step, not a proven fix. Cool head, warm feet: the old saying had it the right way round.
The better-tested way to cool down is, oddly, to warm up first. 7 Ways to Make Every Day Work Better has the warm bath or shower an hour or two before bed: across 17 reports, it shortened the time people took to fall asleep. The warmth brings blood to the skin, and the core cools faster afterwards. A cool bedroom helps it along.
Eat early
The clock is not only set by light. Food sets clocks too, just not the one in the brain.
In 2017, ten young men had their three daily meals moved five hours later for six days. Their brain's master clock did not budge: melatonin and cortisol kept their old timing. But their blood sugar rhythm shifted by nearly six hours, and a clock gene in their fat tissue by about an hour. Late meals had quietly moved part of the body onto a different time zone. Jet lag, without leaving the kitchen.
7 Ways to Make Every Day Work Better has the other half: the same meal raised blood sugar 17% more in the evening than in the morning. So the old advice to make breakfast or lunch the main meal holds up. Build it around meat, fish and eggs, and let the evening meal be the lighter one.
Fasting for jet lag
The tip to fast before a long flight has a real story behind it.
The Argonne diet, developed at a United States national laboratory, alternates days of feasting and fasting before travel. In 2002, it was tried by National Guard troops flying across nine time zones. Of 186 personnel, those who volunteered for the diet had jet lag less often, on the way out and on the way back.
They were volunteers, so the people keen enough to diet may have differed in other ways. It is a hint, not proof. For the main lever on jet lag, 7 Ways to Make Every Day Work Better has how to use light: morning light pulls the clock earlier, which suits flying east, and evening light pushes it later, which suits flying west. Exercise can push the same way. When 99 adults, young and older, did an hour of moderate treadmill exercise on three days at one of eight times of day, exercise in the morning or the early afternoon moved their body clocks earlier, and exercise in the evening moved them later.
Amber, not red
The claim is that red light at night "supports melatonin". The finding is about something slightly different: blocking the blue.
In 2009, 20 adults wore either amber glasses, which block blue light, or yellow ones, which block only ultraviolet, for the hours before sleep, over two weeks. Sleep quality improved more in the amber group. In 2018, 14 people with insomnia wore amber lenses or clear ones before bed, a week of each. Their insomnia scores improved with the amber.
Both tests were small. But dim, warm light in the evening, and amber lenses such as these if you are on a screen, are a cheap way to tell the clock that the day is over. For reading in bed, a dim amber book light such as this lights the page without the blue.
Then make the night itself dark. When 43,722 women were followed, those who slept with artificial light in the room were more likely to be obese, and more likely to put on weight over the following years. It was a link, not proof, but a dark bedroom costs nothing.
And skip the nightcap. The Sleep-Immune Connection, linked below, has why: alcohol gets us to sleep sooner and then breaks up the second half of the night.
Barefoot
Walking barefoot on grass, sand or soil is often sold as "earthing", with claims that it lowers stress hormones and resets the body clock, and with mats to buy for indoors. We could not find a solid test of it for sleep.
That does not make the walk worthless. Barefoot on the grass in the morning is still morning daylight, still fresh air, and still a pleasure. Take it for those, and leave the mat on the shelf.
Scent
A scent you keep only for bedtime can become a cue for sleep.
Aromatherapy Scents for Relaxation and Mood has why: what you expect a scent to do shapes what it does, so if lavender means bedtime, and you use it only at bedtime, it starts to mean bedtime. Lavender also calms in its own right, so it is the one to keep for the evening rather than the desk. A drop or two of an oil such as this on a tissue by the bed is enough, kept well away from small children's faces.
Melatonin
Melatonin is the hormone of darkness, and the bottle feels like a shortcut. It is a gamble.
Why Most Stress Supplements Fail (And the 9 Worth a Look) has the 31 supplements bought off the shelf and tested: the melatonin inside ranged from 83% less than the label said to 478% more, and eight of them also held serotonin, a different chemical altogether. A lucky dip in a bottle. It also has why melatonin works more as a signal to the body clock than as a sedative. Daylight and darkness send that signal for free.
Back to the feet
The Basel team found that sleep starts at the edges: warm hands, warm feet, heat leaving the body as the clock turns towards night. Most of what works for the body clock is like that. It is not a hack. It is giving the clock the signals it already understands: bright mornings, early meals, dim evenings, a cool room and warm feet. Nothing to buy, mostly.
Tonight, put on a pair of warm socks before you get into bed.
Want the whole day in step with your clock? 7 Ways to Make Every Day Work Better — Starting With What Your Body Is Doing — the coffee rule with nothing behind it, the meal your body handles best, why an early night fails, and why flying east is harder than flying west.
Short nights adding up? The Sleep-Immune Connection: What One Sleepless Night Does to Your Defences — where the line for catching colds falls, why nine hours looks no safer than five, how to sleep through a cold, and how to get through the day after a bad night.
Know someone who is wide awake at night and useless in the morning? Send them this, and a pair of warm socks.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional, especially if poor sleep lasts for weeks, if you snore loudly or stop breathing in your sleep, or before taking melatonin alongside other medicines. Never look directly at the sun.
Affiliate Disclosure: This article contains affiliate links. As an Amazon Associate, All For Life earns from qualifying purchases, at no extra cost to you. We only link to products we would recommend without the commission.
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