At Habitual, we think a lot about the complex mix of factors that impacts the ability to lose weight and keep it off. While people often talk about weight loss by focusing on things like calories, diet strategies, and exercise, we’re just as interested in the other lifestyle components—including sleep—which are traditionally left out of the conversation.
To help explain why sleep is so important, this article will cover the physiology and psychology that link sleep to weight, as well as providing some tips on healthy sleeping habits.
One of the many factors which determine how much we eat is hunger. The reverse also applies: Part of what stops us from eating is a feeling of being full. These feelings (hunger and “fullness”) don’t come out of thin air, but are rather triggered by two different hormones: Leptin (the “full” hormone 😋), and ghrelin (the “hungry” hormone 😩).
As it turns out (and this has been shown in scientific research), sleep-deprived people have elevated levels of ghrelin and decreased levels of leptin—and that’s after only one night of poor sleep. In practice, this means their physiological response to lack of sleep is doubly damaging: They feel both more hungry and less full than they would have if they had a full night’s sleep.
Perhaps even worse, this elevated feeling of hunger has been shown to translate into a significant increase in calorie consumption—nearly 400kcal more each day!
This increased consumption is likely due to both these hunger hormones as well as the brain’s response to sleep deprivation, which we’ll dive into next.
Our hunger hormones aren’t the only things impacted by lack of sleep: How our brains make decisions about what, and how much, to eat changes based on how much sleep we have.
When we’re sleep-deprived, research shows that the area of our brain which helps us control impulses and make thoughtful decisions is silenced: That is, our brains are less able to hold us back from unhealthy decisions when we’re not well-rested. To add further insult to injury, what does take over is the area of our brains which drives desire—meaning that we’re much more likely to reach for a sugary or salty snack that we know is unhealthy.
It’s worth noting that the studies cited here aren’t talking about intense sleep deprivation, but rather a night or two of 4-5 hours—which isn’t a foreign concept to many of us. Fourteen percent (that’s around 42 million people!) of Americans regularly get five hours or less of sleep.
Whether you’re actively trying to lose weight or not, it might be helpful to start keeping a sleep diary to see if you can identify any trends linking your eating behaviours to sleep quality. While sometimes there’s nothing you can do about a short night of sleep, it can help to be aware of the impact it will have on your hunger levels and ability to control your impulses related to food.
As we’ve learned, sleep deprivation can impact how we feel towards (and choose!) different foods—but the emotional effects of sleep deprivation in fact reach much farther than simply our interactions with food.
In general, missing out on sleep leads us to be significantly more irrational in our decisions (and therefore the actions we take), which can not only hinder our ability to make healthy decisions, but also negatively impact our work, relationships, and overall happiness. At Habitual, we talk about weight as part of a much broader physical and mental health picture—both of which are important in making sustained behavioural changes.
So what happens when we lose sleep to make us more irrational? It all has to do with our brains. As explained above, the impulse control region in our brains is silenced when we’re sleep deprived—making it harder to make healthy decisions, from what food to eat to how to approach a tough situation at work.
To make the matter worse, sleep-deprived brains also over-activate strong emotions such as anger and the flight-or-fight response. Unfortunately, this can result in a downward spiral, in which you eat something you might not have otherwise because you’re less able to resist the craving, leading you to get angry with yourself for slipping up, which can then negatively impact your interactions with others, meaning you might then eat alone and opt for something unhealthy to help you feel better… you get the idea.
While weight can certainly be impacted by sleep, at Habitual we see weight as only one part of a much larger health picture—so it’s worth a few notes about how sleep can affect your heart and blood sugar.
We all know the factors which can increase our risk of heart attack or stroke, such as smoking and physical inactivity. But as it turns out, sleep can be equally as potent.
After just one night of bad sleep, our heart starts pumping faster, in turn increasing our blood pressure. Sleep deprivation can also (over time) increase the presence of atherosclerosis, or plaques, which lead to unhealthy arteries.
Where does all of this lead? According to one study, to a 71% increase in the risk of heart attack and 45% increase in the risk of stroke.
Your heart isn’t the only organ impacted by a lack of sleep. Sleep deprivation, studies have found, leads healthy (non-diabetic with no blood sugar issues) individuals to be 40% less effective at absorbing glucose—effectively making them pre-diabetic after just one week of short sleep.
It’s no surprise, then, that people who sleep less see far higher rates of type 2 diabetes. This isn’t to say one necessarily causes the other, or vice versa, but there is a conclusive link.
By now, you should have a solid understanding of the links between health, weight, and sleep—and we hope the evidence is compelling enough that you start making changes to your sleep routine if needed! We realise that sleep is individual and different things work for different people, but here are some pointers from the experts:
We realise that it’s nearly impossible to have 8+ hours of great sleep every night, particularly with the stresses of work, family, and everything else that consumes us on a day-to-day. basis But we hope that having learned about the importance of sleep to your health (and the impact it can have on your weight loss journey), you’ll begin to see sleep as a tool for creating a healthier lifestyle.