Are sleep and weight loss connected? 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. But we all experience physiological responses to lack of sleep. Amongst these responses are changes to the secretion of hormones involved in appetite control.
These physiological responses can affect our ability to make good decisions throughout the day, decisions which affect how and what we eat, and may also affect what our body is doing with that 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
When tired we also experience changes to normal concentrations of two neurotransmitters, or nerve messengers, called leptin and ghrelin. Leptin and ghrelin are related to feelings of appetite. Circulating leptin helps you to feel full. Circulating ghrelin triggers your appetite to eat.
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 more than 8 hours a night. The mechanisms may be different if you are male or female. In contrast to women, men seem to have high circulating ghrelin – the appetite stimulant – and may eat more consequent to their levels of ghrelin.
Not enough sleep also reduces the secretion of the appetite suppressing hormone leptin. Even if you eat the same amount of food that you normally eat, you are likely to feel hungrier than normal.
Another hormone secreted by the cells lining the stomach, cholecystokinin, is affected when we are sleep deprived. Cholecystokin increases feelings of fulness when we eat, but when we don’t get enough sleep we don’t secrete the same amount. Again, we eat more consequently.
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 300kcal 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. You are highly unlikely to burn up extra kcal 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 a sleep deprived state suggests that 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. 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, which are usually junk foods. 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 : )