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Tuesday, August 11, 2009

LIFESTYLE AND GENETICS

Diet, exercise, and genetics clearly play a pivotal role in weight. If obesity seems to run in the family, a struggle with weight could be the result of the genes a person inherited. According to the director of the Genomic Laboratory at Laval University Research Center in Quebec, Canada, an estimated 50 percent of obesity cases are due to genes. Currently, there are seven known gene defects that cause obesity.3 A gene defect is a general term for a gene that causes the body to operate in an undesirable way, generally leading to disease. In this case, a gene defect could contribute to obesity, which then leads to heart disease.



Genetics cannot be controlled, but lifestyle can. One lifestyle choice is the hours of sleep a person gets each day. Sleep can factor into one’s weight. Leptin is a hormone produced in the fat cells that signals to the brain that the body has had enough to eat. It is produced in relation to how much you sleep. Not getting enough sleep can drive down leptin levels. This drop in leptin level in turn can lead to overeating because the brain is not receiving the "full" signal. Another hormone that is affected by sleep is ghrelin. Ghrelin is a hormone produced in the gastrointestinal tract that stimulates appetite. Once food enters the stomach, the body halts ghrelin production. A lack of sleep can cause ghrelin levels to rise, leading to an increased sense of hunger. In essence, a chronic lack of sleep can cause a person to want to eat more and feel less satisfied than he or she would otherwise be when well rested.

Studies by the University of Chicago looked at this relationship between appetite and sleep. The researchers measured levels of leptin and ghrelin in 12 men. After those levels were measured the men were subjected to sleep deprivation for two days. Their levels were measured again. Then they received two days of extended sleep and again these hormone levels were measured. This experiment showed that leptin levels went down and ghrelin levels rose when sleep was restricted. The men also indicated that their appetite increased: Specifically, their desire for high-carbohydrate, calorie-dense foods increased by 45 percent.4 This study shows that sleep deprivation may trigger the appetite and increase the likelihood of weight gain. Sleep, however, is just one of the lifestyle factors that affect one’s weight; stress, dietary habits, and level of exercise also contribute significantly.

Source: "Drugs The Straight Facts: Weight-Loss Drugs," Chelsea House, 2009

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