It's no secret that a good amount of sleep can result with increased health benefits, both mentally and physically. Of course, as with anything in life, too much of it can also be bad. It's striking the right balance that matters most.
But what about people who aren't exactly the healthiest, namely those who are overweight and don't get enough sleep?
According to a new study published on JAMA Internal Medicine, researchers have found that increasing the amount of sleep in overweight individuals by an hour can result with reduced daily calorie intake. This has led scientists to a supposed link between sleeping more and losing weight, without making any changes to one's diet.
Sleep and metabolism work together.
IMAGE: Andisheh A / Unsplash
Past studies have shown that an insufficient amount of sleep can drive weight gain in humans, potentially triggered by a decrease in metabolic function. Wanting to look at the opposite end of the spectrum, scientists at the University of Chicago Medicine decided to observe whether increasing sleep would result with weight-loss, especially among individuals who can benefit from it the most – overweight people.
“Over the years, we and others have shown that sleep restriction has an effect on appetite regulation that leads to increased food intake, and thus puts you at risk for weight gain over time,” said lead investigator Esra Tasali.
“More recently, the question that everyone was asking was, ‘Well, if this is what happens with sleep loss, can we extend sleep and reverse some of these adverse outcomes?’”
Working with researchers from the University of Wisconsin-Madison, the team enlisted 80 adults in their randomized clinical trials – all of them overweight and sleeping less than 6.5 hours per night. Naturally, these people are more susceptible to obesity later on in life.
The study lasted a total of four weeks, with the first two weeks used to gather information about the normal duration of sleep the participants got, as well as their calorie intake. After this was done, the participants were split into two groups: Some were told to continue their regular sleeping routine (the control), and the others had their sleep duration extended by an average of 1.2 hours per night. This part of the study lasted for another two weeks.
No other changes to lifestyle or diet.
IMAGE: Pille R Priske / Unsplash
Each night, the participants would sleep on their own beds, and measure the amount of shut-eye they got with wearable sleep-tracking devices. None of them were told to change any other aspects of their lives – not even their diet.
"Most other studies on this topic in labs are short-lived, for a couple of days, and food intake is measured by how much participants consume from an offered diet," said Tasali.
"In our study, we only manipulated sleep, and had the participants eat whatever they wanted, with no food logging or anything else to track their nutrition by themselves."
The scientists then measured the participants' energy expenditure through the "doubly labeled water" method – a process used to replace the hydrogen and oxygen molecules in drinking water with stable isotopes, which can then be traced when they're flushed out of the body. This gives scientists an accurate measure of the amount of calories burned.
“This is considered the gold standard for objectively measuring daily energy expenditure in a non-laboratory, real-world setting and it has changed the way human obesity is studied,” said senior author Dale Schoeller.
IMAGE: i yunmai / Unsplash
Encouragingly, the participants that got an extra hour of sleep managed to show a decrease in food consumption. Some managed to take in less than 500 calories per day. On average, however, the subjects that got more sleep saw a 270-calorie reduction.
While Tasali stresses this wasn't a weight-loss study, the researcher claims there's now quantified evidence of a decrease in calorie intake caused by extending the sleep duration.
"If healthy sleep habits are maintained over longer duration, this would lead to clinically important weight loss over time. Many people are working hard to find ways to decrease their caloric intake to lose weight – well, just by sleeping more, you may be able to reduce it substantially," Tasali said.
“Now we’ve shown that in real life, without making any other lifestyle changes, you can extend your sleep and eat fewer calories. This could really help people trying to lose weight.”
So let's do some simple math (and by no means is this the amount that definitively reduces calorie intake). Considering the fact that the participants got an average of 6.5 hours of sleep before adding on the extra 1.2 hours, we can deduce that a good amount of sleep for calorie reduction is 7.7 hours, or just under eight hours per night.
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