According to the World Health Organization, there are around 2 billion overweight adults worldwide. Of those, 650 million are classified as obese. That equates to 39 percent of adults aged 18 or over who are overweight.
As of 2020, the U.S. adult obesity rate stood at 42.4 percent, the first time the national rate has passed the 40 percent mark, and further evidence of the country’s obesity crisis. The national adult obesity rate has increased by 26 percent since 2008. Rates of childhood obesity are also increasing with the latest data showing that 19.3 percent of U.S. young people, ages 2 to 19, have obesity. (1)
Sleep duration in both children and adults has been decreasing over the past fifty years while at the same time rates of overweight and obesity have been increasing. Short sleep duration along with other dimensions of poor sleep has been associated with obesity. (2)
A 2004 study from the University of Chicago School of Medicine however went further, studying the appetite hormones ghrelin and leptin and their relationship to sleep. Researchers found that partial sleep deprivation altered the circulating levels of ghrelin and leptin causing an increase in appetite and a preference for calorie-dense, high-carbohydrate foods. They further postulated that this could provide a mechanism linking sleep loss to the world’s obesity epidemic.
Ghrelin is known as the “hunger hormone” that stimulates us to eat. Produced in the stomach, it increases when we are hungry. Leptin, which is produced in the body’s fat cells, is the “satiety hormone” which, when our stomachs are full, is triggered to send messages to the brain to tell us to stop eating.
According to professor and research director Eve Van Cauter, Ph.D., “This is the first study to show that sleep is a major regulator of these two hormones and to correlate the extent of the hormonal changes with the magnitude of the hunger change. It provides biochemical evidence connecting the trend toward chronic sleep curtailment to obesity and its consequences, including metabolic syndrome and diabetes.” (3)
Since 1953, the University of Chicago has become famous for studying sleep patterns. Since 1999, however, the Van Cauter laboratory has published a series of studies describing the metabolic and hormonal consequences of chronic partial sleep loss. The question of weight gain with sleep has been of recent focus largely due to the epidemic of obesity in the world.
In 1960, US adults slept an average of 8.5 hours per night. By 2002, that had fallen to less than seven hours nightly. Now, just 23.5 percent, less than one in four young adults, sleeps at least eight hours a night. (3)
In 1960, only one out of four adults were overweight and about one out of nine were considered obese. Now two out of three adults are overweight and nearly one out of three is obese. Whether or not these two trends are connected, however, is unclear. (3)
In their 2004 study, the Chicago research subjects who only slept four hours had a ratio of ghrelin to leptin that was 71 percent higher compared to those who slept ten hours. As hunger increased, food choices changed. After two nights of curtailed sleep the volunteers experienced a surge in a desire for sweets, such as candy and cookies, salty foods such as chips and nuts, and starchy foods such as bread and pasta. (3)
“When you have sleep deprivation and are running on low energy, you automatically go for a bag of potato chips or other comfort foods,” says Susan Zafarlotfi, Ph.D., clinical director of the Institute for Sleep and Wake Disorders at Hackensack University Medical Center in New Jersey. (4)
You might fight off sleepiness, but the ultimate result may be unwanted pounds, as poor food choices coupled with lack of exercise may set the stage for obesity and further sleep loss. Not getting enough sleep (or good quality sleep) causes your metabolism to malfunction. Conversely, if you are a five-hour sleeper and start to sleep for seven hours a night, you may start dropping weight. Why this happens is not understood yet but may be related to the body’s need for glucose after several hours of sleep. Glucose is known to inhibit ghrelin secretion. (4)
More recently, a 2020 study from the University of Pennsylvania School of Medicine showed there is a definite link between sleep loss and obesity. Rather than sleep loss causing obesity, however, they found the opposite to be true, that obesity can cause sleep loss.
They based their findings on experiments using genetically modified microscopic laboratory worms that had stopped sleeping. This resulted in worms accumulating excess fat resembling human obesity. This observation could explain one reason why people with obesity may experience sleep problems. “There could be a signaling problem between the fat stores and the brain cells that control sleep,” said David Raizen, MD, member of the research team. (5)
First, look at how much you sleep vs. how well you sleep. Keep a regular sleep schedule. Trying to catch up on sleep after a week of late nights can cause changes in your metabolism.
Recommendations from the Sleep Foundation:
- Sleep in a dark room: Exposure to artificial light while sleeping, such as a TV or bedside lamp, is associated with an increased risk of weight gain and obesity.
- Don’t eat right before bed: Eating late may influence weight gain.
- Reduce Stress: Chronic stress may lead to poor sleep and weight gain in several ways, including eating to cope with negative emotions.
- Be an Early Bird: People with late bedtimes may consume more calories and be at a higher risk for weight gain. Early birds may be more likely to maintain weight loss when compared to night owls.
- Get regular exercise: Especially if that exercise involves natural light. While even taking a short walk during the day may help improve sleep, increasing daily activity can have a more dramatic impact. (6)