Late nights and appetites: the sleep-obesity connection

According to the W.H.O., worldwide obesity has nearly doubled since 1980. The trend looks set to continue.

Our increasingly sedentary lifestyles, and an abundance of cheap, calorie-dense processed food have now contributed to a situation where 1/3 of the planet is considered overweight or obese.

For a long time, the mantra has been that losing weight is all about diet and exercise. But recent discoveries are suggesting another possible factor for weight gain – what we at Sleep Junkies consider to be the third pillar of health.

The sleep-obesity connection

The rise in obesity over recent decades has been accompanied by a growth in chronic sleep problems. Research has shown that the two phenomena are not unrelated.

Sleep plays a key role in maintaining health, including managing our weight, and lack of sleep is a known risk factor for obesity in both children and adults.

Shorter sleep duration is also linked to higher body mass index (BMI) and the expression of obesity-related genes. Our infographic explains some of the factors that turn sleep loss into weight gain.

The sleep obesity connection

When you’re sleep deprived:

Your hunger hormones kick in

Two major hormones in your body control your appetite and hunger. One is called leptin, or the “appetite suppressor.”  It’s a hormone made by your fat cells to signal to your brain that you have plenty of energy.

When leptin levels are high, your body knows that it isn’t starving and doesn’t need to eat more.  Shorter sleep duration has been found to lead to low leptin levels, and consequently the body increases its energy intake by eating more food.

The other hormone is called ghrelin, a hormone that increases appetite, and also plays a role in body weight. Like leptin, sleep loss affects your grehlin levels too.

Even a single night of sleep deprivation can cause ghrelin levels to rise, making you feel hungrier and more likely to make bad food choices.

Your body temperature drops

Over the course of a 24 hour period, our body temperature fluctuates in accordance with in-built circadian rhythms. Some scientists speculate that sleep deprivation can cause your core body temperature to drop lower than it should.

This drop in body temperature could cause the body to use up energy stores to thermoregulate, leaving a person more tired and drained.

Bad foods seem like a good idea

Some scientists have taken a closer look at the link between obesity and sleep deprivation, and they have found that sleep deprivation can actually increase your desire for high-calorie, weight-gain promoting foods.

A study by Greer et. al (2013) found that the more severe a person’s sleep deprivation, the greater their appetite for junk food.

More time awake = more eating opportunities

Van Cauter et. al (2008) believes that one of the major pathways promoting obesity in sleep-deprived people is that spending more time awake means more time to eat.

She found that certain neurons that increase feeding are active during waking hours and inactive during sleep. In animal models, sleep deprivation increases these neurons’ activity.

Not only does sleep deprivation mean more time to eat, but it may possibly cause increased desire to eat.

You’re more tired

Persistent sleep debt from chronic sleep deprivation causes daytime fatigue , which in turn promotes obesity by discouraging exercise and other calorie-burning activities.  Combined with the increased calorie intake your body may crave as a result of sleep deprivation, this is a recipe for weight gain.

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Full text of our infographic:

Tired of gaining weight? The sleep/obesity connection

Increasing scientific evidence tells us there’s a strong link between lack of sleep and obesity. Here are some of the ways that poor sleep habits can lead to weight gain.


Sleep loss drives down leptin, a hormone that signals you’re full, tricking you into thinking you’re hungry when you’re not.

It gets worse.

Sleep loss increases grehlin, a hormone which signals that you’re hungry, boosting your appetite. A hormonal double-whammy

YOUR BODY TEMPERATURE IS LOWERED Sleep loss can affect your thermoregulation, lowering your core temperaure, causing reduced energy expenditure and more fatigue.

YOU FEEL MORE TIRED Sleepiness spurs inactivity. Lounging on the sofa is not going to help your weight problem.

YOU CRAVE JUNK FOOD Sleep loss increases activity in the ‘reward’ centres of the brain, making you more likely to reach for unhealthy foods high in sugar, salt and fat.

YOU HAVE MORE TIME TO EAT Time can sometimes be your enemy. You don’t snack when you’re sleep- ing! Extra hours awake increase the opportunities for food intake.


WHAT CAN YOU DO? Practice good sleep hygiene:

  • stick to regular sleep/wake times
  • get plenty of natural daylight
  • respect your internal body clock
  • avoid stimulants before bedtime
  • banish phones, laptops, TV from the bedroom

Read more about sleep hygiene –

Get regular exercise –

Maintain a balanced diet –



1 Sleep and Obesity. Harvard School of Public Health

2 Leptin Levels Are Dependent on Sleep Duration. Journal of Clinical Endocrinology & Metabolism

3 A Single Night of Sleep Deprivation Increases Ghrelin Levels Journal of Sleep Research

4 Short sleep duration and weight gain: a systematic review. Obesity.

5 The Impact of Sleep Deprivation on Food Desire in the Human Brain. Nature Communications

6 An epidemiological study: sleep and life style factors in Japanese factory workers. Journal of Phys. Anthropology

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