Stress, computers, television, and long work hours are just a few of the things stealing our sleep – and it could be affecting more than just your energy levels! Nutritionist Cindy Williams and HFG dietitian Zoe Wilson investigate the links between food, sleep and your weight.
Just like following a healthy diet and exercising, sleep is vital for good health and maintaining a healthy weight. While we sleep, our body releases chemicals that control appetite, fight infection, build and repair muscle, promote maturation in teenagers and consolidate memory. So a good night‘s sleep is more important than you may think!
How much sleep do we need?
Our sleep requirements vary at different stages of life, decreasing as we get older. During times of rapid growth and development such as infancy, childhood, teenage growth spurts and pregnancy, our bodies need more sleep.
Infants need 14–18 hours of sleep a day, and toddlers need 12–14 hours. Primary school-aged children need 10–12 hours, teens need 9–11 hours and adults need 7–9 hours of sleep each night. Older people – who tend to sleep lightly and awaken more often during the night – may find they need a nap during the day to meet their needs.
What happens when we don’t get enough?
Sleep deprivation can dramatically affect our mood, making us anxious, depressed, withdrawn, irritable, aggressive or hyperactive. It also affects our concentration – leading to forgetfulness, organisational issues and difficulties with problem-solving. It can also reduce our ability to learn and retain information; affect motor co-ordination; and weaken our immune system, making us more likely to get sick.
The three most common sleep disorders in Australia are:
1. Sleep deprivation (including that resulting from shift work)
Not getting enough sleep, due to a hectic lifestyle or having changing work shifts, can make it harder to get into a routine.
2. Snoring and obstructive sleep apnoea
Snoring affects about 30–40% of adults on a regular basis. It gets worse with age and weight gain, and can disrupt your partner’s sleep, too. Many regular snorers also have a condition called Obstructive Sleep Apnoea (OSA), which occurs when your airway narrows or gets blocked, causing a pause in breathing which leads you to wake up repeatedly.
Common causes of insomnia – which is defined as having difficulty falling or staying asleep night after night – include feeling upset, worried, sad or stressed, or discomfort from an illness, but sometimes there is no obvious cause.
Just as we can accumulate financial debt, we can also accrue a ‘sleep debt’. Even one hour less a night contributes to a sleep debt that must be repaid in order to stay healthy.
The link between sleep and weight gain
When you‘re tired, hormonal changes make it difficult to stick to a healthy eating routine. People often reach for high-sugar/high-fat foods for an energy hit to get them through the day. The consequence of too many days of sleep deprivation, and the follow-on of a poor diet, is often weight gain.
More and more children are not getting enough sleep as well, and researchers have linked this lack of rest to soaring rates of childhood obesity. One study found that infants who slept less than 12 hours a day were more likely to be overweight as toddlers. The same effect also applies to older children: a study of almost 800 children found that those in Year 6 who slept fewer than the recommended 10–12 hours a night were more likely to be overweight. Additionally, those who slept fewer hours in Year 3 were more likely to be overweight when they reached Year 6.
A review of 13 adult sleep studies and seven children’s sleep studies confirms the link between shorter sleep duration and obesity in children. However, while not getting enough sleep has been shown to alter metabolic systems (including blood sugar control and increasing appetite), the review’s authors said there are a number of situational factors that ‘muddied’ the link between lack of sleep and weight gain in adults, making it difficult to draw a definite conclusion.
How sleep affects your hunger levels
What research has proven, however, is that getting less sleep alters the levels of two key appetite-controlling hormones: leptin and ghrelin. Leptin is responsible for telling your brain that it is satisfied or full. Ghrelin tells you when you are hungry.
Lack of sleep, especially when associated with stress, reduces leptin levels and increases ghrelin production, meaning you feel hungrier during the day and eat more but feel less satisfied, which can lead to weight gain.
According to scientists, this weight gain can be slowed just by sleeping a little more. A study published this year followed a group of 18–64 year olds who slept for less than six hours a night for six years. They divided the participants into two groups – one group that still slept for less than six hours, and the other that increased their sleep to 7–8 hours a night at the end of the study. Those participants who increased the amount of sleep they regularly got had a smaller gain in BMI and gained less than half the amount of body fat, compared to the group that continued to get less sleep.
Can certain foods and drinks help you sleep?
Eating or drinking too much may make you uncomfortable when you are trying to sleep. The Australian Sleep Association recommends having your last main meal 2–3 hours before you sleep, but many people find having a snack or warm drink before bed helps their sleep routine. Some commonly-suggested foods and drinks are:
Eating carbs increases the level of tryptophan in your blood, a pre-cursor to serotonin – a sleep-inducing brain chemical. While more research is needed (and some say that the effect may be purely psychological), sleep researchers generally agree that including a carbohydrate such as rice, bread, pasta or potato in your evening meal can help you sleep more soundly.
Milk also contains a small amount of tryptophan, however it’s likely that any perceived sleep-inducing effects of warm milk are psychological. Other foods that contain tryptophan include turkey, eggs and tuna.
Chamomile tea (which is caffeine-free) is often promoted for its relaxing properties. Chrysin, a flavonoid found in chamomile, has been found to have a similar effect to certain sleep-inducing drugs. It’s a good alternative to coffee and black or green tea, which all contain caffeine. Caffeine should be avoided for at least two hours before you head to bed, and up to six hours if you often have trouble sleeping. It can take up to eight hours for the body to eliminate caffeine, so stick to drinking it in the mornings.
Melatonin, which is produced by the brain in preparation for sleep, regulates your body’s wake-sleep cycle. But as we age, less melatonin is produced. Eating just a handful of walnuts before bed has been shown to produce a three-fold jump in blood levels of melatonin, making it easier to sleep.
This over-the-counter supplement is marketed as a way to help overcome insomnia. Older people seem to gain a greater benefit from melatonin, but no convincing evidence exists to prove that it’s an effective treatment for insomnia. It’s generally considered safe to use for a few weeks, but its long-term safety is unknown, so it’s important to consult your doctor before taking it.
Some herbal supplements, such as valerian, may help you sleep, but the evidence is limited. Be sure to ask your doctor before you start taking valerian, as it may interact with other medications and has been associated with liver damage.
Tips for a good night’s sleep
Maintain a routine. Go to bed at the same time each night and get up at the same time each morning. Keeping to a bedtime routine is very important for children, too.
If you want a weekend sleep-in, keep it short. Keep this in mind for teenagers, who tend to disrupt their body clock by going to bed later, and sleeping in longer.
Eat dinner at least two hours before bedtime. Keep it low in fat and spices, and stay away from caffeine, alcohol and cigarettes for at least a few hours before bedtime – they all disrupt sleep.
Have a warm bath, perhaps adding a few drops of lavender oil, before going to bed.
Remove the TV and any other stimulating screen activities from the bedroom. Don’t write, talk on the phone or eat in bed. Some people find reading a book helps them go to sleep, but for others it may be too stimulating.
Keep the bedroom cool, dark and quiet. Assess your mattress and pillow for comfort and invest in some heavy curtains to block out any light. Also turn off any noisy gadgets, like your phone, to prevent them from waking you up.
If you can’t fall asleep after 20 minutes or so, get up. Go back to bed once you feel tired.
If anxiety is keeping you awake, develop strategies to help you deal with the worry. Some examples are: writing down your thoughts and worries in a journal; talking to a friend/family member/partner; breaking down your anxieties into manageable tasks to tackle the next day.
Try to do all your sleeping at night. If you have to nap during the day, keep it to less than one hour. If you do shift work, try to make time for enough sleep (7–9 hours); keep the bedroom cool and dark; and avoid caffeine, sleeping pills or alcohol before you go to sleep. The Sleep Health Foundation recommends sleeping just before going to work, or having a 15-minute nap before you go to work.
Don’t exercise at least an hour before going to bed (it raises your body temperature too high for a comfortable sleep).
Did you know?
An estimated 1.2 million Australians experience sleep disorders
Sleep disorders underlie 9.1% of work-related injuries
Fast facts on sleep
Just under 25% of Australians have their sleep disrupted on a regular basis by others in the household who snore
1 in 5 of those surveyed reported being disturbed 3–5 times per night and almost two-thirds reported difficulty going back to sleep
40% of Australians say they do not wake feeling refreshed and two-thirds feel sleepy during the day more than once a week
Anoja S. Attele, DDS, Jing-Tian Xie & Chun-Su Yuan. 2000. Treatment of Insomnia: An Alternative Approach. Altern Med Rev; 5(3):249-259) Australian Centre for Education in Sleep. 2008. Sleep Facts. Available at URL www.sleepeducation.net.au/sleep%20facts.php. Accessed August 2011. Block J. 2010. Lack of sleep may impede fat loss. J Clinical Outcomes Management; 17(11):491. Breus M, PhD. 2008. Warm milk, true or false? Available at URL http://blogs.webmd.com/sleep-disorders/2008/01/warm-milk-true-or-false.html. Accessed September 2011. Carter PJ, Taylor BJ, Williams SM & Taylor RW. 2011. Longitudinal analysis of sleep in relation to BMI and body fat in children: the FLAME study. BMJ; 342:d2712. Chaput JP, Despres JP, Bouchard C, Tremblay A. 2011. Longer sleep duration associates with lower adiposity gain in adult short sleepers. Int J of Obesity; doi:10.1038/ijo.2011.110. Elder CR, Gullion CM, Funk KL, DeBar LL, Lindberg NM and Stevens VJ. 2011. Impact of sleep, screen time, depression and stress on weight change in the intensive weight loss phase of the LIFE study. International Journal of Obesity; doi: 10.1038 ijo.2011.60. Lumeng JC, Somashekar D, Appugliese D et al. 2007. Shorter sleep duration is associated with increased risk for being overweight at ages 9 to 12 years. Pediatrics; 120(5):1020. Magee L & Hale L, 2011, Longitudinal associations between sleep duration and subsequent weight gain: A systematic review. Sleep Medicine Reviews doi:10.1016/j.smrv.2011.05.005. Mayo Foundation for Medical Education and Research, 2011. Insomnia. Available at URL www.mayoclinic.com/health/insomnia/DS00187/DSECTION=alternative%2Dmedicine. Accessed September 2011. Pejovic S, Vgontzas AN, Basta M et al. 2004. Short sleep duration is associated with reduced leptin, elevated grehlin and increased body mass. PLoS Med 1(3):e62. Pejovic S, Vgontzas AN, Basta M et al. 2010. Leptin and hunger levels in young healthy adults after one night of sleep loss. J Sleep Res; 19(4):552-8. Schmid SM, Hallschmid M, Jauch-Chara K et al. 2009. Short-term sleep loss decreases physical activity under free-living conditions. Am J Clin Nut; 90(6):1476. Sleep Health Foundation. 2011. Common Causes of Inadequate Sleep. Available at URL www.sleep.org.au. Accessed September 2011. Sleep Health Foundation. 2011. Common Sleep Disorders. Available at URL http://www.sleep.org.au. Accessed September 2011. Sleep Health Foundation. 2011. Shift Work. Available at URL www.sleep.org.au. Accessed September 2011. Spinella M. 2006. An alternative approach to sleep, Sleep and Sleep Disorders, Springer Section III:, 297-303, DOI: 10.1007/0-387-27682-3_34 University of Chicago Medical Center. 2010. Sleep loss limits fat loss. Available at URL www.sciencedaily.com/releases/ 2010/10/101004211637.htm. Accessed September 2011. Van Cauter E & Knutson KL. 2008. Sleep and the epidemic of obesity in children and adults. Eur J Endocrinology; 159 Supp 1: 59-66. Wake Up Australia: The Value of Healthy Sleep Report and the Pfizer Australia Healthy Sleep Health Report. Available at URL http://www.stollznow.com.au/downloads/HealthySleep34.pdf. Accessed September 2011. Wurtman RJ & Wurtman JJ. 1995. Brain serotonin, carbohydrate craving, obesity and depression. Obes Res 3 Suppl; 4:477S-480S Zeller JL. 2008. Short sleep duration in infancy and risk of childhood overweight. JAMA; 299(21):2485.