MATTERS IN OBESITY:
“Sleep is the golden chain that ties health and our bodies together” — Thomas Dekkar
The increase in prevalence of obesity in the last 3–4 decades has been paralleled with less sleeping hours for both children and adults. With increasing trends in today’s society for evening and night work hours, as well as for evening leisure time, people are cutting down on the number of sleeping hour they get.
On average, we need about 7.5 hours of quality sleep per night. There is a biological clock working inside our bodies called the ‘circadian rhythm’. Having less than normal sleep disturbs this clock.
But unfortunately not sleeping enough is becoming common — even talked about with pride. Back in 1998, 35 percent of American adults were getting 8 hours of sleep a night, and by 2005 this figure had dropped to 26 percent.
A good night’s sleep is one of the keys to good health — and may also be a key to maintaining a healthy weight. There is mounting evidence that people who get too little sleep have a higher risk of weight gain and obesity than people who get seven to eight hours of sleep a night.
Evidence from cross sectional population studies suggests strong relationship between short sleep duration and weight gain.
A study led by Eve Van Cauter, MD, PhD, Professor of Medicine at the University of Chicago, followed-up healthy men and women with an average body mass index; half were normal sleepers, the other half averaged 6 ½ hours or less. Glucose tolerance tests showed that the short sleepers were experiencing hormonal changes that could affect their future body weight and impair their long-term health. To keep their blood sugar levels normal, the short sleepers needed to make 30% more insulin than the normal sleepers. Eve Van Cauter describes sleep deprivation as “the royal route to obesity.
Sleep and Childhood Obesity:
A number of studies conducted in different countries have almost consistently suggested a link between duration of sleep and obesity in children. For example, in a British study, that followed more than 8,000 children from birth found that those who slept less than 10 and a half hours a night at age 3 had a 45 percent higher risk of becoming obese by age 7, compared to children who slept more than 12 hours a night.
How Does Sleep Deprivation Contribute to Weight gain?
Weight gain can result either by eating more than our body needs or decreasing the calories that we burn. There are several ways that chronic sleep deprivation can do this.
Having less sleep hours can increase energy intake by:
- Hormonal changes:
Ghrelin and leptin are two naturally occurring hormones in the body that have important role in appetite regulation. ‘Ghrelin’ increases the appetite while leptin decreases it. Studies show that sleeping less may alter the levels of these hormones: when we are sleep-deprived blood level of ghrelin increases and that of leptin decreases. Obviously, the combined effects of more ghrelin and less leptin would mean nothing but weight gain.
- More chances to eat out and snack :
It is a common observation that people who stay awake until late night tend to take more snacks during late hours. What happens is that when you have sleep deprivation and are running on low energy, you automatically go for a bag of potato chips or other comfort foods. Late sleepers are also more likely to eat out and have irregular and unhealthy meal patterns.
- Psychological ‘Deception’: The psychological manifestations of fatigue, sleep and hunger are similar. When we are tired because of sleeplessness and our mind is not active enough, it confuses tiredness with hunger and starts pushing us to eat although we are only tired and not actually hungry. The immediate effect of this is that we are able to fight off sleepiness for the time being but the ultimate result is that we put on unwanted weight.
Sleeping less could decrease energy expenditure by:
- Day time tiredness: A very obvious result of sleep deprivation is day time fatigue. People who don’t get enough sleep remain lethargic and tired throughout the day, resulting in decreased physical activity which leads to weight gain. Although indirect, this is almost an inevitable result of sleep deprivation.
- Lowering body temperature: Some laboratory experiments suggest that people who are sleep-deprived tend to have a drop in their body temperatures. This drop, in turn, may lead to decreased energy expenditure. But more research is needed to establish this observation.
Although there is convincing evidence that getting a less than ideal amount of sleep is an independent and strong risk factor for obesity, most of the research done so far, however, consists of observational studies. On the other hand randomized clinical trials are currently underway and we hope to get answers soon with more substantial evidence.
Nevertheless, based on the extensive knowledge we already have on the health benefits of good & sound sleep, there is little risk in encouraging healthy sleep through lifestyle changes, such as setting a consistent bedtime, limiting caffeine late in the evening and avoiding unnecessary late night activities.
- National Sleep Foundation: 1. National Sleep Foundation. 2005 Sleep in America Poll. Accessed June 14, 2011
- Harvard School of Public Health: 1.Patel SR, Hu FB. Short sleep duration and weight gain: a systematic review. Obesity (Silver Spring).2008; 16:643–53. 2. Patel SR, Malhotra A, White DP, Gottlieb DJ, Hu FB. Association between reduced sleep and weight gain in women Am J Epidemiol.2006; 164:947–54.
- Susan Zafarlotfi, PhD, clinical director, Institute for Sleep and Wake Disorders, Hackensack University Medical Center, New Jersey.