I’m starting to get to the point in life when I worry about my parents (and other middle-aged relatives) getting old and sick. I think it’s more pronounced because of my job – I see patients younger than my parents in the hospital with heart attacks, hip fractures, and other age-related ailments. Luckily, my dad is a pretty healthy dude. He has always been active, riding his bike to work for years, using free weights in his garage, and doing yoga at work (which he organized as part of his workplace wellness initiative). He eats lots of fruits, vegetables, lean proteins and whole grains (white bread was forbidden in my home growing up). He gets regular physicals, monitors his cholesterol and blood pressure, and even meditates. He’s the poster child for wellness – except for one major problem. He’s sleep deprived.
He recently told me he gets about 6 hours of sleep a night. He stays up late watching TV in bed. When I regaled him with the detrimental effects of sleep deprivation on health, he scoffed. He didn’t seem particularly interested in changing his ways. I compared him to a soda addict. He rolled his eyes.
(Now, to some of you out there, 6 hours of sleep might seem like a rare blessing. If that’s the case, and you’re getting by on 3 or 4 hours a night, you should definitely keep reading. )
Humans need sleep like they need oxygen and food. Although there is no magic number of hours of sleep that is sufficient for everyone, the general consensus (according to the National Sleep Foundation’s expert panel) is that adults over age 26 need 7-9 hours a night. The functions of sleep include physical regrowth of muscle and blood vessels, conservation of energy, immunity, cognitive ability, and mood. Sleep deficiency is linked to cardiovascular disease, kidney disease, hypertension, and diabetes, and is a risk factor for obesity. 1
As a dietitian counseling overweight and obese clients, I am particularly interested in the obesity/sleep connection. At first glance, the link appears to involve a strong hormonal influence. Two hormones that play important roles in appetite, hunger, and regulation of food intake are leptin and ghrelin. Ghrelin works to stimulate hunger and increase food intake, while leptin signals satiety and a decrease in food intake. (In grad school, I kept these two straight by thinking of a stomach grrrowling when Ghrrrelin is high. You’re welcome). Disrupted or lack of sleep causes decreases in leptin and increases in ghrelin (like a homeostatic response to the increase in energy expenditure experienced during wakefulness when compared to sleep).2 The chronically high grhelin levels lead to increased hunger and food intake. The effects last all day, all week, all month – as long as you’re sleep deprived.
But some research suggests there is more at play than a homeostatic response. After all, we eat (and abstain from eating) for a lot of reasons that don’t involve physical hunger. We eat for comfort, in response to stress, for pleasure. We eat to reward ourselves. We eat (or don’t eat) when we’re sad. We have ‘good days’, when we resist the donuts at the office, and ‘bad days’, stopping for a Starbucks extra-whip Frappucino on the way home. These are all examples of the hedonic drive to eat.
There was a study published in 2013 in the journal Psychoneuroendocrinology that examined this3. The researchers used 19 healthy men to test whether sleep deprivation overnight would affect the amount of food eaten at breakfast and during snacks the next day. The study had a within-subject design, meaning the same participants were subjected to both the control (8 hours of sleep) and the intervention (total sleep deprivation) conditions. The morning after each respective experimental period, but before feeding the participants breakfast, the researchers asked the men to select their ‘ideal portion size’ of 7 different meal items and 6 different snack foods, using computer-generated images. Meal item and snack portion size was larger when the subjects were sleep-deprived compared to when they slept 8 hours. They asked them to do this portion size task again after feeding them breakfast. Even in the absence of physical hunger, the subjects chose larger portions of snack foods when they were sleep deprived compared to when they slept well. While the elevated grhelin levels in the sleep-deprived state might explain the larger portion size choices in the group (indeed the researchers measured the grehlin levels in the study), something else must have influenced the increased snacking after breakfast among the sleep-deprived state.
Lack of sleep and your brain
Lack of sleep may affect how your brain’s reward centers react to pleasurable stimuli. More specifically, some research has shown that pleasurable things may seem even MORE rewarding in the setting of sleep deprivation4. However, some studies in children and adolescents found the opposite – the reward response was dampened by sleep restriction.5,6 Either situation, though, could theoretically lead to an increase in reward-seeking behavior.
Your brain needs sleep to function properly, to get organized, to plan. Sleep deprivation impairs the part of the brain that manages executive control7. This part of the brain is useful in setting health-related goals like packing lunch instead of eating out, eating breakfast every day, or going to the gym after work. When executive control is, well, out of control, you’re less likely to stick to these plans, and more likely to give in to your reward signals (those would be the ones telling you to eat sugar and fat). Research shows that when executive control is impaired, people tend to eat more calories overall7,8,9.
You don’t need me to tell you that sleep deprivation has a negative impact on your mood. Adequate sleep helps you effectively respond to emotionally distressing situations. This is why we tend to want to ‘sleep on it’ before making an emotionally-charged decision. Research has shown that when people are restricted in sleep, they tend to have a ‘glass is half empty’ outlook on life. They remember negative stimuli more than positive ones, and they are more pessimistic10,11. When you’re in a bad mood, you just want to feel better, right? You want to feel calm and comforted. And broccoli won’t cut it. What do the emotionally distressed reach for in their time of need? You guessed it – only highly palatable foods with lots of sugar and fat stimulate those reward centers enough to turn that frown upside down.
More research exploring the connection between abnormal sleep cycles, like those of night shift workers, and food intake (both hedonic and homeostatic) still needs to be done. It is likely, however, that a strong relationship does exist, and that efforts to get more quality sleep could pay off when it comes to reaching our goals of eating healthier.
Since I’m a dietitian, not a sleep specialist, my advice for getting more, better sleep will come from an outside source. Here’s a list of strategies for improving your sleep straight from the website of the National Heart Lung and Blood Institute10 (of course my dad is getting a special email version of this list):
- Go to bed and wake up at the same time every day. For children, have a set bedtime and a bedtime routine. Don’t use the child’s bedroom for timeouts or punishment.
- Try to keep the same sleep schedule on weeknights and weekends. Limit the difference to no more than about an hour. Staying up late and sleeping in late on weekends can disrupt your body clock’s sleep–wake rhythm.
- Use the hour before bed for quiet time. Avoid strenuous exercise and bright artificial light, such as from a TV or computer screen. The light may signal the brain that it’s time to be awake.
- Avoid heavy and/or large meals within a couple hours of bedtime. (Having a light snack is okay.) Also, avoid alcoholic drinks before bed.
- Avoid nicotine (for example, cigarettes) and caffeine (including caffeinated soda, coffee, tea, and chocolate). Nicotine and caffeine are stimulants, and both substances can interfere with sleep. The effects of caffeine can last as long as 8 hours. So, a cup of coffee in the late afternoon can make it hard for you to fall asleep at night.
- Spend time outside every day (when possible) and be physically active.
- Keep your bedroom quiet, cool, and dark (a dim night light is fine, if needed).
- Take a hot bath or use relaxation techniques before bed.