We have all heard it. Perhaps some of us have even said it. Phrases like “No willpower” and “Can’t push away from the table” are frequently used to disparage an overweight or obese person’s perceived lack of “motivation” to control his or her eating habits. But, is this really the primary reason why weight gain occurs?
It is a simple nutritional principle that if calories consumed exceed calories expended, weight gain will result. Therefore, most weight reduction programs focus on cutting calories. Many people view failure to adhere to these regimens as a lack of motivation, dedication, or mental toughness. However, there is now increasing evidence that the “lack of willpower” may be explained by chemical and hormonal changes resulting from sleep deficiency.
There are more and more data that support a link between obesity and insufficient sleep. The growth of this country’s obesity epidemic over the past 40 years correlates with a progressive decline in the amount of sleep reported by the average adult. In large population-based studies, obesity has been found to be related to reduced amounts of sleep. But if this association is true, how might sleep deficiency be related to weight gain?
A recent experimental study published in the journal Sleep provides some clues. Sleep restriction to 4.5 hours per night was compared with normal sleep duration for 4 nights each in a group of young, healthy adults. When measured at the end of 4 days, the ratio of 2 hormones responsible for hunger levels, ghrelin (which increases appetite) and leptin (which reduces appetite) was altered to favor greater appetite. Other studies have observed the same thing. However, this study measured something the others hadn’t: snack consumption, particularly items with greater fat and protein content, was higher after sleep restriction — and, strikingly, the participants’ levels of endocannabinoids increased corresponding to the time of greater snack consumption. Endocannabinoids are chemicals that kindle appetite (like ghrelin), but more importantly, also stimulate reward centers in the brain. Thus, this finding suggests that sleep restriction may make the act of eating more satisfying. Could it be that insufficient sleep contributes to weight gain by stimulating the brain to make eating more pleasurable? If so, the “lack of willpower” may not be due to personal weakness, but rather a result of an addictive chemical imbalance resulting from sleep loss.
No doubt that this exciting finding requires further investigation. However, it already provides additional evidence that sufficient sleep is important for optimal health, and in particular, for combating obesity. It also suggests that greater efforts need to be made on the part of public health officials, individual clinicians, and the general public to get the 7 hours or more of nightly sleep recommended by the American Academy of Sleep Medicine.