Sleep and weight: why sleeping more can help you eat less

When people try to lose weight, they focus on food and exercise. Sleep rarely makes the list. But research shows that how long you sleep affects how much you eat, and that sleeping more may be one of the easiest changes to make.

Too little sleep: you eat more, but don't burn more

A systematic review and meta-analysis in the European Journal of Clinical Nutrition pooled studies in which people's sleep was deliberately shortened ^[1]. Eleven studies with 172 participants provided enough data for the analysis. After partial sleep deprivation, people ate about 385 kcal more per day than after normal sleep ^[1].

At the same time, their energy expenditure and resting metabolism did not change significantly ^[1]. In other words, short sleep adds calories without burning more of them. The extra calories came mostly from fat, with slightly less protein ^[1].

Sleeping more: a trial in real life

The more practical question is whether the reverse works. A randomised clinical trial published in JAMA Internal Medicine tested this in 80 adults aged 21 to 40 with overweight who usually slept less than 6.5 hours a night ^[2].

After two weeks of normal habits, half of the participants received a single, personalised sleep hygiene consultation aimed at extending their time in bed. They slept in their own beds, tracked their sleep with wearable devices and received no advice on diet or exercise ^[2]. Energy intake was measured objectively with the doubly labelled water method, not with food diaries.

The results over the next two weeks ^[2]:

• sleep increased by about 1.2 hours per night compared with the control group;
• energy intake fell by about 270 kcal per day;
• energy expenditure did not change significantly, so the sleep extension group was in a negative energy balance.

The more sleep participants gained, the more their energy intake fell ^[2].

How much sleep do you need?

The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults aged 18 to 60 sleep 7 or more hours per night on a regular basis ^[3]. Regularly sleeping less than 7 hours is associated with weight gain, diabetes, high blood pressure, heart disease and depression ^[3].

How certain is this?

Most of the studies in the meta-analysis lasted from one day to two weeks and took place in laboratories, and the authors called for longer studies ^[1]. The trial was short, small and done in young adults with overweight. It was not designed to measure weight loss, and the authors say longer studies are needed to know whether the effect lasts ^[2]. Still, the direction of the evidence is consistent: shorter sleep goes with eating more, and longer sleep with eating less.

How to sleep longer

• Keep a fixed wake-up time, including at weekends, and go to bed earlier rather than sleeping in.
• Put screens away before bed. Phones and laptops in bed are one of the most common reasons sleep gets shorter.
• Make the bedroom cool, dark and quiet.
• Avoid caffeine in the afternoon and heavy meals or alcohol close to bedtime.
• Get daylight in the morning to help set your body clock.

If you snore loudly, wake up feeling unrested despite enough time in bed, or have trouble sleeping for weeks, talk to your doctor. Conditions such as sleep apnoea and insomnia need proper diagnosis and treatment.

If you want a plan that combines nutrition with everyday habits such as sleep, see how the personalised meal plan works.