Is sleep affecting your weight?

Have you ever considered if lack of sleep is affecting your weight?  Well, if you ever find yourself perusing the contents of the fridge or  bread bin after a night of interrupted sleep,  you will know. Subjectively, we all report feeling hungrier after a bad sleep. Why we are more hungry is complicated, and still being researched.

Physiology and Decision Making

Mechanisms between men and women may be different,  but we all experience physiological responses to lack of sleep. Amongst these responses are changes to the secretion of hormones involved in appetite control.  Appetite hormones are hormones that affect how hungry we are, or how full we feel.  It makes complete sense that changes to these hormones will affect our ability to make decisions around eating throughout the day. Below, we  look to decisions which affect:

how we eat

what we eat, and

how the body is handling food.

Sleep and Insulin

When we are sleep deprived we are less effective at absorbing glucose from the bloodstream into our cells.  Usually insulin is secreted when we eat. Insulin  acts as a carrier of glucose from the bloodstream into the cell, and is  necessary for uptake of proteins too. When we are tired our cells don’t seem to respond to insulin in the normal way. Our cells seem to become resistant to insulin. It’s a little like if you were to ignore the postman who has a package for you, and is knocking on your door. You don’t answer, and the postman leaves the package behind. When the cell doesn’t open and let insulin deliver glucose, the insulin and the glucose are left circulating in the blood stream. Too much circulating of either compound is not considered healthy.

Women, particularly, seem to experience higher circulating levels of insulin, and may eat more because their insulin resistant cells are still craving glucose to fuel cell functions.

Leptin and Ghrelin and Cholecystokinin (CCK)

When tired we also experience changes to normal concentrations of  leptin, ghrelin and CCK. These are  compounds which act as hormones and also as neurotransmitters or nerve messengers.  Leptin, ghrelin and CCK have many different functions, some of which will be affected by how much sleep we get.

Circulating leptin helps you to feel full.

Circulating ghrelin triggers your appetite to eat.

Cholecystokinin slows down gastric  (stomach) emptying, and so affects our feelings of being full.

When put through sleep deprivation trials (4 – 5 hours of sleep allowed), healthy individuals report feeling much hungrier than when they are allowed to sleep 8 or more hours per night.  Measured hormone levels in trial participants suggests that:

Not enough sleep

Reduces the secretion of leptin so we feel less full.

Increases the secretion of ghrelin so we feel hungrier.

Reduces the secretion of CCK, so we feel less full.

Even when we consume the same amount of food as we might normally, you feel hungrier, and less full, so may be triggered to consume more than usual.  Changes in hormones are only part of the story: is sleep affecting your weight?


Another interesting finding  is the increased production of endocannabinoids when we are sleep deprived. Endocannabinoids  are chemicals very similar to the chemicals produced by marijuana. Result? We are more likely to increase our intake of snacks following a poor night of sleep – we get ‘the munchies’ – further increasing our intake of calories.

And what do we crave with the munchies?

Sweets – chocolate, biscuits and ice cream

Carbohydrate rich foods such as bread and   pasta

Salty snacks like crisps and pretzels

How much more do we eat when sleep deprived?

Research suggests that on average after being sleep deprived, we eat almost 400kcal more than normal.

Are you burning more kcal because you are awake for longer?

And if you think you are burning more kcal because you are awake versus being asleep, think again. Sleep is an intensely active period of calorie burn for the body and the brain anyway. You are highly unlikely to burn up a significantly greater number of  kcal than usual, just because you are awake.

Do we switch off parts of our brains?

Research using MRI scanning and looking at individuals who have enjoyed a good night of sleep or are in a  sleep deprived state see differences.  Areas of the brain which are involved in ‘thoughtful judgements and controlled decisions’ are silenced with sleep deprivation. Instead, deep seated areas of the brain which are more primitive and automatic, parts of the brain which would drive us to seek calorie rich foods and so help us to survive, are activated.  We seem to lose the ability to more consciously consider what we eat. We can create and try to stick to good habits of course, it’s just more challenging.

Body composition effects

What’s also interesting to note is what happens if we are dieting. When well rested we  tend to reduce our weight primarily from fat stores, whereas when we are sleep deprived there can be  more of a loss of lean tissue.

Is sleep affecting your weight? Yes!

Hopefully by now you will see it is really important to get a good night’s sleep. For me, a good sleep is the foundation upon which healthy lifestyle related decisions sit. A variety of hormones are involved in sleep, many of which affect your appetite and your ability to manage your weight.  The mechanisms by which they play out may be different between men and women, but we all tend to eat more if we don’t get enough sleep. We  eat more junk food, or foods which we find comforting, even bigger servings of healthy food than normal.  If we manage to keep to a calorie prescription to enable weight loss, we may lose lean tissue rather than fat. So create a good sleep routine, and watch the weight loss happen.

Please contact me if you would like help with a healthy lifestyle.

Felicity Lyons

Hi there! My name is Felicity. I am a registered dietitian and sports nutritionist with a proactive approach to healthy living. My job is to interpret the complexity of nutrition science and translate it into messages and guidance that you can understand. Healthy Living? It's easier than you think!