Sleep and weight. What research shows about short sleep and hunger

Several studies link sleep with hunger and with how much fat you lose on a diet. Here you will find what has been measured, how certain it is and what you can do on days when you have slept too little.

How much sleep an adult needs

The American Academy of Sleep Medicine and the Sleep Research Society recommend that every adult sleeps 7 hours or more each night. The US National Sleep Foundation gives 7 to 9 hours for adults and 7 to 8 for older adults. The UK health service (NHS) gives the same range, 7 to 9 hours. According to the two American societies, young people, people who are ill and people who have lost sleep over the previous days may need more than 9 hours.

These recommendations came from expert panels that examined the available studies. It is very certain that the experts agree on 7 hours as the minimum.

What changes in your appetite when you sleep too little

Most studies on this subject are done in a laboratory. The volunteers sleep normally on some nights and less on others, and the researchers measure what they eat and how much energy they burn.

Two analyses brought these studies together:

• A 2017 analysis of 11 studies and 172 people. After short sleep the participants ate about 385 kcal more. The energy they burned did not change significantly. They also ate more fat and less protein.
• A 2019 analysis of 41 randomised studies. Short sleep increased hunger and intake by about 250 kcal a day. With less sleep, weight rose on average by 0.34 kg.

The results are of low certainty. The studies were small and lasted from a few days to two weeks. All of them, though, show that when we sleep too little we eat more, while the body does not burn enough extra to balance it out.

The ‘hunger hormones’

You often read that short sleep raises ghrelin, which increases appetite, and lowers leptin, which reduces it. This was shown in a well-known 2004 study of 12 young men. After two nights of short sleep, leptin fell by 18%, ghrelin rose by 28% and hunger by 24%. They mainly wanted foods high in calories and carbohydrate.

The larger 2019 analysis, with 41 studies, found no consistent change in these hormones. So it is more certain that we eat more after short sleep. We don’t know yet for certain why this happens.

Sleep while you are dieting

A 2010 study put 10 adults with excess weight on a two-week diet, twice. One time they had 8.5 hours in bed and the other time 5.5 hours. The calories were the same both times.

The scales showed the same drop, but with short sleep less fat and more fat-free mass was lost. The participants also felt hungrier. It was only 10 people for two weeks, so the finding is of low certainty. It does fit with the rest, though.

If you sleep more, do you eat less?

A 2022 trial in the US took place at home, not in a laboratory. It included 80 adults aged 21 to 40 with excess weight, who slept less than 6.5 hours. Half of them had one session with a counsellor about sleep habits. The rest changed nothing.

• The first group slept about 1.2 hours longer each night.
• They ate about 270 kcal less a day than the other group. Intake was measured with an objective method, not a food diary.
• Over two weeks the difference in weight was 0.87 kg.

It is one study and it lasted two weeks, so the result is of low certainty. We don’t know whether the difference lasts for months. But if you regularly sleep less than 6.5 hours, more sleep may also help with hunger.

Population studies show something similar. In an analysis of more than 600,000 adults, people who slept little had obesity more often. This link does not prove that sleep is to blame, because people also differ in many other ways.

What to do on days when you have slept too little

The ideas that follow have not been tested in studies. They come from the findings above.

• Expect more hunger. Keep a filling snack with protein ready, such as yoghurt or an egg, for the time when you usually get hungry.
• Don’t ‘punish’ the next day with less food. Carry on as normal.
• Watch alcohol and caffeine in the evening. The NHS lists them among the common causes of insomnia. For alcohol, see also the related article.
• Don’t draw conclusions from one day’s weigh-in. Look at the weekly average, as we explain in the article on plateaus.

When to talk to a doctor

Talk to your doctor if any of the following applies:

• You have trouble falling asleep or wake up often for 3 months or more, or your sleep affects your day.
• You snore loudly, someone has seen you stop breathing in your sleep, you wake up choking or you are tired all day. This may be sleep apnoea.
• You feel very sleepy while driving. Don’t drive when you are very sleepy, and talk to a doctor.

For chronic insomnia, the 2023 European guideline recommends as the first treatment a form of cognitive behavioural therapy designed specifically for insomnia. Sleeping pills are recommended only for a short time, up to 4 weeks. If you are thinking of taking something for sleep, even without a prescription, ask your doctor or pharmacist first.