Esra Tasali says that adequate sleep is essential to preventing obesity.Credit: University of Chicago Medicine
A healthy diet and regular exercise have long been staples of weight management. But research shows that the role of sleep, which helps to regulate appetite hormones and calorie intake, is just as important. Esra Tasali, a sleep specialist at University of Chicago Medicine in Illinois and director of the UChicago Sleep Center, spoke to Nature about why getting sufficient sleep could be crucial to weight loss and maintenance.
How did you end up studying sleep and weight loss?
My sleep journey started about 25 years ago. I had completed my pulmonary training and decided to specialize in sleep medicine. I also trained in endocrinology, so it was natural for me to study the relationship between sleep and metabolic diseases, including obesity and diabetes.
Would you say that sleep is as important for the body as it is for the brain?
Absolutely! Sleep is inextricably linked to our biology and important for every cell in the body. Work at the University of Chicago has challenged the brain-centred view of sleep. As far back as 1999, we published a paper1 that showed that healthy young men who did not have obesity or diabetes, when sleep-deprived in a laboratory setting, show signs of prediabetes. And now we have the research to show that sleep is essential to regulating metabolism, appetite and hormones.
Why does not getting enough sleep make us more susceptible to weight gain?
Lack of sleep increases our drive to eat. There are two main reasons that this could happen. The first is that when we are sleep-deprived, our brain’s reward centres are more active and drive us to seek rewards. These include food, particularly high-calorie, unhealthy food. Our ability to inhibit the impulse to eat is diminished.
Nature Outlook: Sleep
The second mechanism driving increased calorie intake is elevations in appetite hormones. The most well-known is ghrelin, the ‘hunger hormone’, which is mainly secreted by the stomach. If you don’t sleep enough, levels of that hormone will be higher, and you will feel hungrier and consume more calories. Over the long term, this leads to weight gain. In 2022, we showed2, in a real-world setting while people continued their daily activities in their home environment, that if you extend sleep by an average of 1.2 hours per night and monitor the energy intake among adults who are overweight, they decreased their intake by an average of 270 calories per day.
How many hours of sleep should people aim for if they are trying to lose weight?
In our study, we aimed for 8.5 hours of time in bed. So, a target of at least 8 hours in bed — and no less than 7 hours of sleep — would be a good start for an adult. But any increase in sleep time seems to help. Interestingly, we found an association between an increase in sleep duration and a decrease in calorie intake. Even an extra 30 minutes of sleep reduced the number of calories consumed.
Many people would like to get more sleep, but have difficulty doing so. What kind of sleep intervention did you use in the study?
We personalized the sleep-hygiene instructions — that is, we tailored them to each person’s schedule and specific needs. One strategy that worked for almost all participants was to insist that they put their electronic devices away at a certain time so that they wouldn’t hear those beeps and dings that draw them into social media, texting or e-mail.
Does weight loss help sleep apnoea, in which a person’s breathing during sleep is interrupted?
Yes — for people with sleep apnoea, a 10% reduction in body mass index reduces the apnoea’s severity by about one-third3. And if you lose weight and improve your sleep apnoea, that might reduce your risk of type 2 diabetes, or make it less severe if you already have it. The fragmented, low-quality sleep associated with sleep apnoea, however, can compound the risk of obesity. So there’s a kind of a bidirectional interaction between excess weight and sleep apnoea.
So, it’s not just the duration of sleep, but also sleep quality that plays a part in metabolism and diabetes risk?
Yes, slow-wave sleep, often called deep sleep, is a key marker of sleep quality. This stage of sleep helps with memory consolidation, restoration at the cellular level and tissue repair, and the clearing out of metabolic waste products. It also has an important role in metabolism and hormonal release. For example, a major pulse of growth-hormone secretion occurs during slow-wave sleep.
Our experimental work4 has shown that if you deprive healthy young adults of slow-wave sleep — to the levels seen in older adults, or in people with sleep apnoea — they show signs of prediabetes after just three days. This finding opened up an area of research that focused on the role of sleep quality in diabetes risk. And data emerging from large population studies suggest that adults who get sufficient slow-wave sleep have a lower future risk of developing diabetes. So finding ways to get enough slow-wave sleep seems to be important, particularly for younger people.
Can wearable technology help people to get better sleep?
Wearables have allowed people to become more aware of their sleep needs and patterns by helping them to monitor their sleep passively. But they don’t necessarily know what to do with this information they’re getting about their own sleep. What is missing are guided, personalized solutions to improve sleep for each individual. That is what we are working on in our new study. I think that, increasingly with wearables, people will start to see how their sleep is connected with other health parameters, such as heart rate, blood pressure and oxygen saturation. They might notice that improvement on those metrics correlate with better sleep, which can, in turn, lead to a change towards healthier sleep behaviours.
How important do you think sleep is in the larger realm of weight-loss strategies?
Getting enough sleep could really help to tackle the obesity epidemic. Its impact could be particularly great for younger people. We know that the obesity epidemic is even more pronounced than it used to be in children and young people. Teenagers are sleep-deprived for various reasons, including heavy use of electronics, social media, video gaming and, in some places, early school start times that work against teenagers’ natural circadian rhythms. To compensate for that sleep loss, they increase their food intake because they tend to be hungrier and reach for unhealthy foods, putting them on a high-risk trajectory for weight gain. So stopping that weight-gain spiral before it starts, at an early age, through healthier sleep habits, has enormous public-health implications for prevention or reversal of obesity.
New weight-loss drugs, known as GLP-1 agonists, are effective against obesity. Is it still important to emphasize the importance of sleep in maintaining a healthy weight?
Despite the increasing interest in the positive effects of GLP-1 agonists, there is still a lot of uncertainty about their long-term biological effects and how they will ultimately change people’s eating habits and lifestyle behaviours. They make you feel less hungry, but they also come with side effects and they’re quite expensive. Plus, when you stop these drugs, you rapidly regain weight. Sufficient sleep can also make you feel less hungry and help you to eat healthier foods; and the good news is that sleep is free, has no side effects, and has many other benefits to overall health and well-being.
More from Nature Outlooks
More than one-third of US adults are not getting enough sleep on a regular basis, which strongly increases their risk of chronic conditions, including obesity, diabetes and cardiovascular disease. Lack of sleep is estimated to cost the US economy close to half a trillion dollars per year. So I strongly believe that educating the public about the importance of adequate sleep in maintaining a healthy weight is crucial to preventing obesity and curbing the epidemic of chronic disease.
