As evidence continues to mount around the link between poor or insufficient sleep and the risk of obesity and metabolic disorders, a group of researchers in the US has seen fit to explore the flip side of this equation. The scientists have found that extending the nightly sleep duration of overweight subjects can lead to a significant reduction in daily calorie intake, so much so it could drive significant weight loss if the pattern was sustained over the long term.
A growing list of studies have shed light on the way sleep loss or irregular sleep can drive weight gain in humans, illustrating how it can lead to metabolic alterations at a tissue level and drive metabolic dysfunction. A study from October last year also showed how an extra hour's sleep for newborns can help lower their obesity risk during the formative months of life.
“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 from the University of Chicago Medicine. “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?’”
The study also involved researchers from the University of Wisconsin-Madison, and explored this question via a randomized clinical trial involving 80 adults. These subjects were overweight and had habitually short sleep duration, of less than 6.5 hours a night, a recognized risk factor for obesity. The idea was to investigate whether extending their sleep duration could mitigate this risk, with the subjects taking part in a four-week study, the first two weeks of which were used to gather baseline information on sleep and caloric intake.
Subjects were then randomly assigned sleep hygiene counseling, which extended their sleep duration by an average of 1.2 hours per night, while some were made to continue their regular sleeping habits to act as a control group. This took place over two weeks, in which all subjects slept in their own beds, tracked sleep with wearable devices and were made to otherwise continue their regular lifestyles and diets.
"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 used what's known as the "doubly labeled water" method to precisely track the subjects' energy expenditure. This technique was pioneered in the 1980s and involves drinking water in which the oxygen and hydrogen molecules have been replaced with stable isotopes that can be easily traced as they are flushed out of the body, enabling measurement of every calorie 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.
The extra 1.2 hours sleep on average led to a large decrease in food consumption among the subjects, with some eating as much as 500 fewer calories per day. On average, the intervention led to an average reduction of 270 calories consumed and resulted in a calorie deficit among the participants, albeit over a short period of time.
“This was not a weight-loss study,” said Tasali. “But even within just two weeks, we have quantified evidence showing a decrease in caloric intake and a negative energy balance – caloric intake is less than calories burned. 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.”
Questions remain over why the increased sleep duration led to a decrease in calorie intake. The authors do note that sleep restriction studies suggest alterations to appetite-regulating hormones and reward centers in the brain may drive overeating after limited sleep. They hope to explore the underlying mechanisms of effects of extended sleep through further studies.
“In our earlier work, we understood that sleep is important for appetite regulation,” said Tasali. “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.”
The research was published in the journal JAMA Internal Medicine.
Source: University of Wisconsin-Madison
