Our hectic lives mean we’re sleeping less than ever. We’re also heavier than ever. Yvonne Kerr asks whether our ‘sleep debt’ is making us fat.
We’ve all been there. Whether it’s due to a crying baby or jet lag, to shift work or a late night, missing out on sleep makes the next day pretty unpleasant. We tend to be cranky and can find it hard to stay motivated or focus.
During sleep, the body does the opposite and goes to work. The pituitary gland, for instance, secretes a growth hormone and a thyroid-stimulating hormone into the bloodstream. Both of these hormones help maintain a healthy metabolism. If we fail to catch precious shut-eye, our levels of these hormones drop, creating a hormonal imbalance.
But lack of sleep does more than make us grouchy and throw our metabolism a curve ball. As sleep-medicine expert Dr Alex Bartle explains, when we’re very tired, our ‘sleep debt’ alters the two main hormones that regulate our appetite: hunger-stimulating ghrelin and appetite-regulating leptin. Without adequate sleep, ghrelin levels rise and leptin levels fall, potentially ramping up our appetite and driving us to eat.
“When you’re overtired, you’re also hungrier, regardless of your weight,” explains HFG nutritionist Claire Turnbull. “So even if you’re overweight — and have plenty of available fuel — your body will still want you to eat more.
“You’re also unlikely to reach for fresh food, such as fruit or a salad,” adds Turnbull. “To give yourself an energy boost, you’re probably more inclined to grab chocolate, chips or a sugary drink (even though that won’t help in the long run!). Basically, fatigue can prompt you to make poor food choices and consume more kilojoules than your body needs.”
Is your sleep pattern making you fat?
Reams of international research link lack of sleep with weight gain. In a major US study, adults who consistently slept for less than 5 hours a night were up to 40 per cent more likely to become obese than were those who slept for seven to eight hours.
Sleep deprivation is a risk factor for weight gain for several reasons. A sleep-starved person may be too tired to exercise and therefore miss out on the health benefits and kilojoule burn that would counterbalance any weight gain. And less sleep gives us more waking hours, which offer more opportunities to eat. Again, any sleep shortfall upsets the balance of key hormones that control our appetite, so we feel hungrier when we’re tired and tend to make poor food choices.
Could your diet be disrupting your sleep?
The foods you eat have a huge impact on your sleep patterns. Most of us learn this the hard way, tossing and turning after a rich or heavy dinner, but other foods are more surprising suspects. Here are the top sleep saboteurs:
Fatty, spicy foods
Chilli and garlic can give some people heartburn and indigestion, both of which turn sleep into a challenge. Fat-rich foods, such as creamy pasta and heavy curries, can also trigger heartburn. On top of that, fat delays digestion, leading to restless sleep.
Caffeine keeps you alert, making it hard to drift off and potentially causing a lighter snooze. This stimulant has a half-life of five to seven hours, meaning that five hours after you’ve finished your coffee, you’ll still be feeling the effects of half its caffeine. (Even 10 hours later, the caffeine can be at 25 per cent strength.) So if you struggle to fall asleep, you may want to reconsider that post-lunch coffee. Other caffeinated beverages, such as cola, energy drinks and some teas, can also interfere with sleep if you drink them too close to bedtime.
Cocoa beans contain caffeine. Dark choc is healthier than other varieties, but it also contains more cocoa, and therefore more caffeine.
Although a glass of wine seems to help us wind down in the evening, alcohol makes it harder to have a deep, restful sleep. Your body takes about an hour to process one standard alcoholic drink, so if you enjoy a tipple with dinner, put the bottle away after you’ve eaten. (Drinking to excess can also make you snore loudly, which may not keep you awake, but can disrupt the sleep of the person next to you!)
Water and other drinks
If you drink anything within 90 minutes of bedtime, you’re likely to wake up to urinate and then have to find sleep all over again.
Meals too close to bedtime
Eat dinner at a sensible time, ideally two to three hours before bedtime. This will ensure you’ve digested your meal well enough to enjoy a sound night’s sleep.
Women and sleep
Women need roughly 20 more minutes of shut-eye than men do, according to a leading authority on sleep. This is because the female brain is highly active.
“One of sleep’s main functions is to allow the brain to recover and repair itself,” says Professor Jim Horne, director of the Sleep Research Centre at Loughborough University in England. “During deep sleep, the cortex — the brain region responsible for thought, memory, language and so on — disengages from the senses and goes into recovery mode. The more you use your brain during the day, the more it needs to recover and, consequently, the more sleep you need.
“Women tend to multitask — they do lots at once and are [mentally] flexible — so they use more of their actual brain than men do. Because of that, their sleep need is greater. A man who has a complex job that involves a lot of decision-making and lateral thinking may also need more sleep than the average male — though maybe still not as much as a woman does.”
Hormones in flux
We blame female hormones for many problems (practically everything!), and now we can add lack of quality sleep to the mix. New research reveals that women’s sleep requirements differ from those of men in other ways, and that these needs have yet to be widely recognised.
Studies show that when some women are in the second phase of their menstrual cycle (after ovulation, when progesterone and oestrogen levels dip sharply), they have lower-than-usual levels of the sleep hormone melatonin. As melatonin is critical to a good night’s sleep, this drop can make it difficult for some women to fall asleep and stay there.
Bouts of insomnia and fatigue affect both perimenopausal and postmenopausal women. About 50 per cent of women aged 40–60 years have trouble sleeping, and this is linked to sleep apnoea (see ‘Sleep disorders’ below) as well as to the hot flushes that result from fluctuating oestrogen levels.
For many mothers, fatigue is one of the first signs of pregnancy. More and more research shows that quality sleep is essential to the healthy growth of your baby and to a smooth transition from pregnancy to early motherhood.
Following childbirth, fatigue is the natural (and expected) result of the sleeplessness due to your newborn’s waking throughout the night. Up to 60 per cent of all new mothers experience the blues within the first two post-partum weeks, but up to 15 per cent of women go on to develop postnatal depression — and experts now recognise that sleep deprivation is a contributing factor. Mothers with the worst depressive symptoms at four and eight weeks after delivery are more likely to report having less than six hours’ sleep in a 24-hour period.
The blue light emitted by televisions, computer screens and smartphones suppresses the body’s production of melatonin, a hormone that helps you fall asleep at night. If your melatonin levels are insufficient, sleep can become even more elusive. Take a break from all your electronic screens in the evening, especially just before bedtime.
There’s nothing worse than staring at the ceiling all night. Unfortunately, many of us are familiar with insomnia, the most common sleep disorder.
Transient insomnia persists for only a week or two, but if sleeplessness continues for weeks or on a regular basis for more than six months, the problem is chronic insomnia.
The lying awake at night makes insomnia easy to recognise, but people with obstructive sleep apnoea (OSA) continue to sleep even as they struggle to breathe.
Apnoea literally means ‘without breath’. Its breathless pauses can last anywhere from 10–30 seconds or for up to a minute or more, and they result in broken, poor-quality sleep. In a bad case, the sufferer can stop breathing up to 700 times a night, and this leads to daytime sleepiness, a typical consequence of OSA. Loud snoring can be a tell-tale sign of OSA, but it’s not proof that someone has this disorder.
Women often present with symptoms that aren’t typical OSA warning signs. They may be suffering from headaches, a lack of energy, fatigue, insomnia, or a combination of these. Some women are also embarrassed by snoring, a classic OSA symptom, so they’re less likely to report this ‘unladylike’ habit.
In addition, some physicians have a preconceived idea of the typical sleep-apnoea patient, whom they see as a middle-aged overweight or obese man, so they don’t look for the disorder in these women.
10 tips for better sleep
Establish regular times for sleeping and waking.
Try not to nap during the day — your nana nap might steal sleep from you that same night.
Avoid alcohol. It might make you feel drowsy, but it’s a major sleep thief.
Avoid caffeine- and sugar-rich drinks in the evening.
Don’t smoke before you go to bed. In fact, don’t smoke.
Encourage a good night’s sleep with a spirited bout of exercise. Just ensure you leave more than three hours between your workout and bedtime — physical activity can make you feel more alert.
Eat your last meal two to three hours before bedtime, and don’t have a big dinner just before you hit the sack.
Catch some rays every day. Exposure to natural light is essential to the production of the sleep hormone melatonin. If the sun isn’t too strong, leave your sunglasses at home.
Limit bedroom activities to sleep and sex. Don’t sit up in bed to watch television, do crosswords or study.
Keep your bedroom cool, dark and quiet.
How much sleep do we need?
Our sleep requirements depend on our age. Here’s the latest advice from the US National Sleep Foundation (2015):
Newborns (0–3 months):14–17 hours a day
Infants (4–11 months): 12–15 hours
Toddlers (1–2 years): 11–14 hours
Preschoolers (3–5 years): 10–13 hours
School-age children (6–13 years): 9–11 hours
Teenagers (14–17 years): 8–10 hours
Younger adults (18–25 years): 7–9 hours
Adults (26–64 years): 7–9 hours
Older adults (65+ years): 7–8 hours
Sleep science: Short sleepers
Do you ever think you might be one of those rare people who don’t need much sleep? If so, you have what scientists call a ‘short sleep’ gene, meaning you require only five to six hours’ sleep a night. People who have a ‘long sleep’ gene need up to 10 hours of shut-eye every night. However, the vast majority of us (97 per cent) need seven to nine hours of sleep every 24 hours.
Did you know? We eat an extra 1500 to 2100kJ (about 350 to 500 more calories) the day after a bad night’s sleep.