Sleep and Weight Gain (Metabolism): The Connection
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Not getting enough sleep is related to weight gain. Before you watch another episode on Netflix, check out the effect that sleep (and lack of sleep) has on your metabolism.
Each year UBC Dietetics Students work with dietitians to practice writing articles for the public. This year, I asked students Cali and Hillary to look into the research to answer a question that I’m asked by clients all the time: what’s the connection between sleep and metabolism. In other words, is their lack of sleep causing their metabolism to slow down and cause weight gain? Here’s what Cali and Hillary found.
First, note that in the scientific research, ‘sleep deprivation’ is most commonly defined as 5 or less hours of sleep per night. Which might mean that your ‘normal’ actually means that you’re sleep deprived.
What Happens When We Sleep?
Sleep helps us recover from damage during the day. Having good sleep helps us regulate our physical activity and food intake. Our bodies are smart. Our organs are programmed to either store fat or use it as energy based on our sleep/wake cycle - independent of food intake. This means that our sleep patterns are a factor linked to how well our bodies regulate our metabolism independent of whether you eat everything ‘right’.
Sleep’s Correlation With Obesity
Many studies show that sleep deprivation is correlated with increased risk for obesity. Sleeping 5 or less hours per night is associated with a greater odds of obesity among both men and women.
Sleep fragmentation was also associated with an increased BMI (new parents – this one you’ll recognize).
On the other hand, the lowest mean BMI was associated with 7.7 hours per night.
Exactly how this works is still unclear. But we do know that sleep deprivation causes a hormonal imbalance that is correlated with altered fat and glucose metabolism (sugar metabolism). It has been found that when our organs receive nutrition from food at an inappropriate time (e.g. for night shift workers) it can increase your risk for weight gain, heart disease, and type 2 diabetes.
Sleep and Fat Metabolism
Now, how does this work?
An important thing to understand about sleep is there are two major stages: 1) deep sleep and 2) rapid eye movement (REM) sleep. In REM sleep your brain is highly metabolically active. The first half of the night is predominantly deep sleep. The second half of the night is predominantly REM sleep.
When our sleep is disrupted during the night we typically lose out on some deep sleep. This leads to excessive tiredness during the day. This extra tiredness may reduce fat burning and satiety (feeling full) after meals. The effect: we’re more prone to fat accumulation.
When we have insufficient amounts of sleep, we tend to lose out on some REM sleep. This is the stage of sleep when our brains are most metabolically active and therefore use up the most energy. This lost time during metabolically active sleep is associated with obesity. These correlations suggest that both the first half and the second half of our sleep are important indicators for fat metabolism.
Appetite
Hormones are what tell us if we are hungry or full. Sleep deprivation can alter our hormonal balance. Studies show that leptin, an appetite suppressant hormone, is lower in sleep-deprived participants. What’s more is that levels of ghrelin, a hunger promoting hormone, were increased in sleep-deprived participants. Study participants also reported a significant increase in hunger and appetite. The studies end there. But you and I can imagine the rest of the story: sleep deprivation leads to feeling hungrier, which makes you eat more, which leads to weight gain.
Limitations in the Research
However, there are limitations to these implications. Further research is needed on the directionality of causation - for example, it’s possible that obesity leads to decreased sleep quality. Or, it may be bidirectional, meaning that each impacts the other.
Additionally, the studies on sleep and fat metabolism are not conclusive. Not all studies reflect real world situations. More research is needed to validate their findings.
Sleep and Weight Gain (Metabolism) Summary
Studies show that sleep deprivation may:
Increase fat storage after a meal.
Decrease fat usage and increase fat storage during sleep.
Decrease physical activity during the day due to excessive tiredness.
Decrease fullness after meals.
Cali and Hillary’s Final Thoughts
There’s no doubt that sleep is important for our all-around health. But while the correlation between both metabolism and obesity with sleep deprivation brings up some interesting questions, the current evidence just isn’t strong enough to show that sleep deprivation directly leads to weight gain. Further research is needed to really understand this relationship. Also, we have to remember that sleep fits into a larger picture of what a healthy lifestyle looks like, and we must note that a nutritious diet, adequate physical activity, minimized stress, and healthy social connections all also play an essential role.
Kristen’s Final Thoughts
Once I point out the potential connection between sleep and hunger/satiety, clients notice that their cravings increase on days when they didn’t get enough sleep. I include increasing sleep to the minimum of 7 hours as an action when I’m working with clients for weight loss. So turn off the screens and get to sleep. Both sleep quantity and quality are important. If you have poor quality sleep, work with your health professional to determine the root cause and take action to improve your sleep.
Thank you Cali and Hillary for your work on this post.
Photo by Sanah Suvarna on Unsplash
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