Although diet and exercise programmes usually dominate the weight loss headlines, research suggests that your sleep habits may be just as important. The latest piece of research showing a link between sleep habits and weight gain appeared in the June 10, 2019 issue of JAMA Internal Medicine.
This paper found that exposure to artificial lighting at night predicted weight gain over 5 years of follow-up among more than 43,000 women. This article, however, is merely the latest of hundreds of scientific papers from the last decade indicating that poor sleep makes it easier to gain weight and harder to lose weight. Because there is now such a large and diverse body of research on the metabolic effects of sleep, many people find it difficult to understand the practical implications. For example: 1) How, precisely, do our sleep habits affect our weight? 2) How can we translate this research into individualised recommendations that can help us personally? This post will address each of these practical questions.
Three mechanisms in the sleep-weight relationship.
For practical purposes, the sleep-weight relationship can be understood in terms of three pathways that we can call: a) The energy pathway; b) The hormone pathway; and c) The nutrient pathway. Although these three pathways overlap in practice, breaking them down into separate pathways makes it easier to see how our individual sleep habits may be affecting us.
a). The energy pathway represents the effects of sleep on our energy and fatigue levels. A reduction in either the quantity (# of hours) or quality of our sleep results in reduced energy levels and less motivation for physical activity. Not surprisingly, when people are sleep-deprived, they are less likely to exercise; even if they push themselves to exercise, however, it is usually for shorter periods and at lower intensity levels. The result is a reduced metabolic rate that could affect our weight if it became a pattern.
The energy pathway effect is not limited to formal exercise, unfortunately. Studies show that sleep deprivation also results in less movement even outside of exercise. This means the energy pathway effect of sleep applies even to people who never exercise. With less sleep, we tend to sit and lie down more, while standing and walking less. We even fidget less and move more sluggishly after a poor night of sleep. This means that, compared to a well-rested version of ourselves, we burn fewer calories all day long when we are struggling with sleep.
b). The hormone pathway has been one of the important recent discoveries in sleep research. This research shows that sleep is closely related to our appetite and other hormones. The authors of the recent JAMA Internal Medicine paper, for example, suggested that light exposure at night might nudge people towards weight gain by interfering with melatonin levels that our brains produce to help regulate our sleep cycles. Disrupted melatonin levels, in animal studies, reduce sleep quality and increase eating.
Sleep research in humans also indicates that several metabolic hormones are disrupted. A pair of appetite hormones called leptin and ghrelin – regulating our feelings of fullness and hunger, respectively – are affected by sleep in precisely the way that you’d expect to cause weight gain. Ghrelin levels increase with poor sleep, producing more hunger. And leptin levels reduce, requiring more food to feel full. Even our body’s response to insulin changes in response to sleep. Poor sleep forces our pancreas to secrete a larger amount of insulin to metabolise food compared to when we are better rested. A combination of less melatonin and leptin and more ghrelin and insulin is a disaster for a person concerned about their weight.
c) The nutrient pathway, finally, refers to how sleep influences our eating patterns in ways that promote weight gain. When people are sleeping poorly, this usually means that they are awake more. And the more hours a person is awake, the more times they tend to eat. People awake during late night and early morning hours, for instance, may snack or graze to stay alert. Compared to a person who sleeps eight hours per night, a person sleeping just 4-6 hours can easily consume an entire extra meal during these extra hours (more than offsetting whatever extra energy they might burn by being awake).
Secondly, sleep also changes our food preferences. Research shows that cravings for sweets and energy-dense foods increase when we are sleepy, probably because our brain is seeking quick energy sources. Not only are we likely to eat more when sleeping poorly, therefore, we are also likely to eat higher calorie foods and with predictable consequences for our weight.
How can we apply sleep-weight research to our individual benefit?
Unfortunately, sleep problems are not always easy to solve. Work schedules, family commitments, and health conditions are just some of the many barriers to a good night’s sleep for many people. This doesn’t mean that effective treatments do not exist, of course.
There are many good treatments for sleep apnea, for instance, as well as both behavioural (CBT-i) and medication treatments for insomnia. Even if these treatments aren’t effective or available, however, there are also ways to think about your individual sleep circumstances that can offer some helpful solutions.
Source: Psychology Today