The weight loss benefits of a regular sleep routine
Posted on 3 January 2019
Sleep expert Dr Alison Bentley, a GP at the Wits Donald Gordon Medical Centre, explains the link between your circadian rhythm and your body’s ability to function optimally.
Your body functions according to various monthly, weekly and daily cycles. The daily cycle is the most sensitive to change, and is made up of circadian rhythms. These regulate your sleep patterns, digestion, body temperature, blood pressure and other physiological and psychological factors. Your daily circadian rhythm is best described as your 24-hour internal clock.
Your circadian rhythm, controlled by the hypothalamus, is completely biological and dependent on melatonin, known as the sleep hormone. Melatonin is released by the pituitary gland and is secreted when the day is coming to an end and darkness sets in – it tells your body it’s time to sleep. The release of melatonin causes your body temperature to drop, which causes sleepiness as well as a decrease in blood pressure; the gut goes into resting phase, and the body’s functions slow down for sleep.
At dawn, when the sun rises, melatonin production ceases and you become alert, ready for an active day.
Keeping in sync
Your circadian rhythm thrives on regularity. Disruptions of the 24-hour cycle of light and dark, such as shift work, long-haul flights across time zones, working all night to beat a deadline, or even exposure to the white light of a computer screen before bedtime can throw your circadian rhythms out of sync and upset your sleep cycle.
Dr Bentley uses flying across time zones as a good example: “Your body takes about one day to recover for every hour of the time zone change. You can get your sleep/wake patterns back into sync fairly quickly by being awake during the day once you’ve arrived at our destination, but you won’t feel right – you’ll feel fatigued, you’ll go to the toilet at the wrong time, and feel hungry at the wrong time. You’re not designed to eat during the night, and when you do, you don’t metabolise food properly. The change in time zone throws your circadian rhythms out of their normal regular patterns. It takes some days to revert to regularity.”
Interrupting your circadian rhythms frequently can, over the years, have long-term effects on our health.
“There is good evidence to show that people who work irregular and demanding shifts over a long period of time have an increased risk of medical disorders, including cardiovascular disease, gastrointestinal disease, cancer, depression and suicide,” says Dr Bentley.
Effect of lack of sleep on body weight
It is often thought that poor sleep patterns can result in a weight increase. Dr Bentley explains the main factor is sleep deprivation, from any cause. While there are some hormonal changes at work, a lot of the weight gain is due to your psychological reaction to the biological effect on your rhythm.
“Sleep deprivation, irrespective of its cause, upsets your circadian rhythm. If you don’t get enough sleep, your brain will be on the hunt for energy – and the easiest and quickest energy source is high-calorie snacks. This is usually combined with the fact that when you’re sleep deprived, you have less energy and tend to be less active. Consuming more calories than you burn can only lead to, over time, an increase in body weight.”
Dr Bentley’s five tips to a better sleep
Clean up your sleep
Reduce the amount of alcohol, nicotine and caffeine you ingest. You cannot expect your biological system to work well if you’re changing your biology with stimulants.
Know your sleep pattern
(i) Know how long you need to sleep for. We’re all told we should sleep for eight hours, but Dr Bentley says the normal range for sleep is anything between four and nine hours. “You need to know what works best for you – if four hours is right for you, then spending eight hours in bed is a waste of time,”
(ii) Know whether you’re a morning person (a ‘lark’) or a night person (an ‘owl’). “Owls can stay up late without feeling tired, and prefer to wake up late; a lark goes to bed early and will wake up early. It’s important to know what works best for you, so you can get the best sleep you can.”
Do the maths
Give yourself enough time to get to sleep. “If you know that you need seven hours of sleep, and you give yourself only six, you’re undercutting your sleep by an hour each night.”
Having a regular bedtime and wake-up time gets the circadian systems in place so that your biorhythms are all working together when you try to go to sleep. “If you’re constantly getting to bed at different times of the night and morning, your biology gets confused and the chances of your getting a good night’s sleep, diminish. We can’t hope to get the psychology right if we’re not giving the biology a chance.”
If you can’t sleep…
“Lying awake for hours in the dark, waiting to fall asleep, is useless. When you’re lying there, you ruminate (the same thought goes through our head over and over again), then you catastrophise (every little molehill becomes a mountain), and you become anxious. Then there’s no chance of falling asleep! Rather get up, even if it’s for an hour or two, and do something productive, even if it’s as simple as deleting emails or tidying cupboards. Within an hour or so, you’re likely to feel sleepy and can achieve a few hours of quality sleep. The way the biology of sleep works, the following night we’re likely to sleep a whole lot better and be able to catch up the lost hours.”