Sleep and lose weight - Tony Ferguson

Can sleeping more help you lose weight?

The straightforward answer is yes! And the cause may be simpler than we (or at least I) previously imagined. Sleep and its effect on weight has been one of the more surprising and little-known aspects associated with weight increase. This could be due in part to a lack of awareness of how sleep impacts weight. According to research, sleeping less affects your hunger hormones (making you hungrier while making it harder to feel full) as well as your stress and adrenaline chemicals, which may impede you from digesting and processing the energy in food. 

Well, some intriguing clinical research has revealed a quite different picture. This study gathered 16 healthy adults and kept them in a lab for two weeks while their sleep, energy needs, and appetite hormones were constantly monitored. The study has two major components. The adults were given either 9 hours or 5 hours of sleep per day for 5 days (similar to a typical work week). To guarantee that no one missed out, they divided the group and had half start with 5 hours and progress to 9 hours, while the other part started with 9 hours and was subsequently limited to 5 hours (stick with me... this will become essential later!). The participants also had unrestricted access to high energy and highly processed snack foods (e.g. crisps, biscuits, chocolate, lollies etc).

So here is a summary of what happened to people who slept less than 5 hours a night for 5 days straight:

  • Their energy needs increased by about 9% (burned more energy over 24hours)
  • Their appetite hormones changed for the better (less hungry and more fullness hormones)
  • They ate more food – mostly after dinner and mostly in the form of carbohydrates.
  • They ate a smaller breakfast than usual
  • They felt significantly more exhausted
  • They gained weight (almost 1kg on average) in just 5 days!

And this is what happened to those who could sleep up to 9 hours a night for 5 days straight:

  • They ate less (especially fats and carbohydrates)
  • Lost a little bit of weight (if they were in the 5 hour sleep group to start with)


So what does all this mean?

According to the researchers, a lack of sleep does seem to lead to weight increase, but not for the reasons we previously thought. It is possible that because we are awake for longer periods of time, we require more energy, and our bodies are designed to use food to keep our energy levels up when we are tired. This could explain why the participants in the study ate considerably more after supper, when they were most likely sleepy, in an effort to stay awake (sound familiar?).  Carbohydrates are a natural choice when you're weary because they are our primary source of energy. Nothing beats a chocolate bar for a pick-me-up!

A circadian rhythm and melatonin may explain why the adults in the study ate less breakfast.  Your circadian rhythm is responsible for waking you up in the morning and preparing you for bed in the evening. It is also the cause of jet lag! This is referred to as our internal body clock. This clock works with melatonin, which rises in the evening and assists us in falling and staying asleep. Because these participants were waking up earlier than usual, their melatonin and body clock told them it wasn't time to eat yet.


So what are my top take-away tips for sleep and weight

  • Well if it wasn’t obvious – get some more sleep! J
  • If you do need to reduce your sleep (cue the crying baby) – try getting up earlier rather than staying up late to get things done. You may be able to avoid the night-time munchies and focus on a good breakfast!!
  • If you find it hard to get up early and need to stay up late – then for goodness sake, don’t keep fun snack foods in the house! Make sure there are plenty of nutrient dense carbohydrates around such as fruit, yoghurt, glass of hot milk, a small tin of baked beans etc.

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By Anna D’Arcy, Accredited Practising Dietitian

My Nutrition Clinic