Statistics have consistently shown a correlation between obesity and sleep deprivation, but only since 2000 have researchers begun to understand why. Individuals who have a BMI of 30 or higher, considered obese, sleep fewer hours each night than those whose body mass indexes fall into the normal range. In studies beginning in 2004, the University of Chicago has traced this to two newly-discovered hormones and the effects of exhaustion on the diet.
Studies
In a study published in the Annals of Internal Medicine in December 2004, researchers at the University of Chicago limited subjects to only four hours of sleep per night. Their appetites spiked 24 percent and they mostly craved sweets. Six years later, in a study published in the Annals of Internal Medicine in October 2010, researchers at the same university studied 10 people with BMIs in the overweight and obese categories. The subjects were placed on a monitored diet intended to have them lose weight without additional exercise. Half of them were permitted adequate sleep, and the other half were restricted to approximately five hours per night. Those whose sleep was restricted lost 55 percent less body fat than the other group.
Effect on Hormones
The discovery of the hormones ghrelin and leptin explain the link between sleep and overeating. The stomach produces ghrelin, which signals to the brain that you need to eat more. Fat cells produce leptin, which increases the metabolism and signals the brain to stop eating. In the 2004 University of Chicago study, researchers found that when their subjects were deprived of sleep, their ratios of ghrelin to leptin increased by 71 percent. In the 2010 study, ghrelin levels in those subjects who were deprived of sleep rose from 75 ng/L to 84 ng/L over the two-week period.
Effect on Decision-Making
The 2010 study subjects also exhibited a change in what they ate when they got inadequate sleep. After two nights of shortened sleep, they began craving sweets, cookies and cake. The researchers theorize that when the brain, powered by glucose, struggles from fatigue, it demands more energy in the form of simple carbohydrates. They also acknowledge that exhaustion might deprive dieters of the willpower to make healthy food choices.
Recommendations
According to Robert Vorona, a sleep researcher at Eastern Virginia Medical School, adults should strive for 7 to 7½ hours of sleep per night. To optimize the hours you devote to sleep, don't fall into habits that will sabotage a good night's rest, especially if you are dieting and attempting to lose weight. Eat your last meal or snack at least one hour prior to bedtime and avoid carbohydrates that will bump up your body's production of insulin. Avoid alcohol. It might make you drowsy, but it won't let you fall into the deep sleep that your body needs to balance the production of ghrelin and lectin.
References
- ScienceDaily: Sleep Loss Limits Fat Loss; Oct. 5, 2010
- "The Washington Post": Sleep's Role in Weight Loss Remains a Mystery; Jennifer LaRue Huget; Apr. 8, 2010
- American Academy of Sleep Medicine: The Sleep Diet -- A Link Between Sleep & Weight Loss?; Jun. 18, 2007
- The University of Chicago Medical Center: Sleep Loss Boosts Appetite, may encourage weight gain; Dec. 6, 2004
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