Poor sleep can lead to weight gain, but now researchers say the relationship works both ways. Studies consistently show that sleep deprivation is linked to obesity and that heavier individuals tend to report more problems getting a good night’s slumber. Now researchers at Johns Hopkins University School of Medicine report at the 2012 American Heart Association Scientific Sessions in Los Angeles that weight loss, either through diet or a combination of diet and exercise, can lead to better sleep.
For six months, the researchers followed 77 overweight or obese individuals with type-2 diabetes or prediabetes. At the start and end of the study, the participants filled out sleep surveys detailing their sleep problems such as sleep apnea, fatigue, insomnia, restless sleep, excessive sleep and use of sedatives. The scientists also measured the volunteers’ body mass index (BMI)to track changes in weight.
The participants were then separated into two groups. The first group went on a weight-loss diet with exercise training and the second group simply stuck to a diet programme.
At the end of the six months, both groups experienced a weight loss of about 6.8kg on average and a 15 percent reduction in belly fat. And factoring in a composite score representing their overall sleep health, the authors found both groups also equally boosted their sleep quality by about 20 percent.
“The key ingredient for improved sleep quality from our study was a reduction in overall body fat and, in particular, belly fat, which was true no matter the age or gender of the participants or whether the weight loss came from diet alone or diet plus exercise,” said study author Kerry Stewart, a professor of medicine at John Hopkins.
According to Stewart, belly fat is particularly concerning since it can be metabolically detrimental to health. “Belly fat is almost like a living organ. It produces proteins that cause inflammation,” says Stewart. “When you lose a lot of belly fat in particular, the level of those substances go way down, and the inflammatory response is much less than it was before.”
That means that rates of heart disease may decline as belly fat dissolves. Inflammation aggravates blood vessels, which can increase heart-disease risk, and also interferes more generally with the body’s normal physiological processes. The end result is obesity, and obesity in turn puts added mechanical pressure on the heart and lungs. “If you have a lot of belly fat, the lungs can’t expand as well, so it becomes harder to breathe when you’re sleeping, which is why more people get sleep apnea,” says Stewart. “When you have sleep apnea, you wake up more in the middle of the night, and that leads to daytime sleepiness and fatigue. So people are feeling miserable because they haven’t had a good night’s sleep.”
Shedding extra weight and increasing physical activity triggers a drop in inflammation and can lower insulin resistance and improve metabolism. “This can foster weight loss or prevent further weight gain,” says Stewart.
Whether sleep problems cause obesity, or obesity causes sleep disturbances isn’t clear, although it’s likely both processes are at work simultaneously. “We are not exactly sure where the problem starts, but we think it is a vicious cycle. Regardless of where it starts, they feed off each other,” says Stewart.
Earlier studies have suggested sleep deprivation leads to overeating and disruptions in circadian rhythms that put you at a higher risk for heart disease, obesity, depression and even type-2 diabetes. Not getting enough sleep can also lead to hormonal changes in men and women that can disrupt hunger signals and stimulate appetite or lessen feelings of satiety. The good news is that the latest studies show that if poor sleep can lead to obesity, losing weight can help you get some more Z’s.