Lack of sleep is a widespread problem. According to a recent survey by sleep support company Tru2U, nearly 60% of Kiwis don’t get enough sleep or feel well rested. And that’s a real concern, as sleep deprivation is harmful to our health. Sleep apnoea, for example, which many adult New Zealanders have, is linked to an increased risk of cardiovascular disease, stroke, diabetes and death.
A single night’s bad sleep promotes biological ageing in older adults by activating certain gene expression patterns, US scientists have discovered. Sleep deprivation also impairs thinking in a similar way to alcohol consumption, compromising accuracy and speed of response when performing tasks. I can vouch for that, given I reversed my car into a closed garage door in the sleep-deprived weeks following the birth of my first child.
Garage doors aside, scientists are particularly intrigued by the increase in obesity that’s occurred alongside our shrinking sleep schedules. Observational studies have revealed a link between lack of sleep and weight gain in adults.
A recent multinational study of children from 12 countries found evidence that short sleep duration was linked to obesity, along with high television viewing and low levels of moderate to vigorous physical activity.
Short-term clinical trials, too, have found restricting sleep results in weight gain in healthy adults. One inpatient study subjected half of the 16 adult participants to five days of limited sleep (five hours’ sleep a night), the five days being equivalent to a working week. The sleep-deprived participants gained an average of 0.82kg over the course of the 14-day study.
Interestingly, our total daily energy expenditure increases by about 5% when we’re short of sleep, so lack of physical activity isn’t the cause. Rather, clinical trials have found people eat more, particularly in the evening, when they’re sleep-deprived. The Gemini Twin Study in Britain found children who slept less than 10 hours a night consumed 50kcal more a day than children who slept between 11 and 12 hours.
Sleep deprivation leads to increased snacking, more meals a day and a preference for energy-dense foods, such as potato chips, chocolate bars and MallowPuffs (or so I’ve heard). This increase is driven by changes to our desire for palatable foods rather than appetite hormone changes.
Eating for pleasure, rather than hunger, is common, thanks to the wide availability of palatable foods. Neuro-imaging experiments have found sleep deprivation heightens the hedonic stimulus processing in the brain that underlies our drive to eat. In particular, sleep-deprived brains display the strongest activation when we’re shown images of unhealthy foods.
But even a good eight hours’ sleep can’t prevent the potentially harmful effects of social jet lag for many adults – a common phenomenon among alarm-clock users. Social jet lag has also been linked to metabolic dysfunction and obesity, most recently among Dunedin Longitudinal Study participants.
Sleep is strongly influenced by social activities, particularly work schedules. This becomes apparent when we compare our sleep on work days with free days, when we may sleep significantly longer.
The phrase “social jet lag” was created to describe this condition, which is defined as the difference between mid-sleep times on work days and days off. Using an alarm clock to wake ourselves in the morning, for example, can prematurely interrupt our sleep. In the course of the week, this accumulated debt is repaid by oversleeping on our free days.
One Dutch study found 70% of the population had an hour or more of social jet lag. And as with travel jet lag, this affects sleep quality, digestion and performance, with mounting evidence that living against our internal clock may disrupt our metabolism and health.
Whether it’s late bedtimes, poor sleep quality or interrupted sleep, a lack of sleep in our obesogenic environment is a dietary accident waiting to happen, leaving us vulnerable to overeating and poor food choices. The start of daylight saving can make sleep doubly challenging, so beat the clock change and get started on improving both your quality and quantity of sleep.
Words by: Jennifer Bowden
Photos by: Getty Images
