to compensate, the blood-glucose levels will increase. This resembles impaired glucose tolerance, which can result in type 2 diabetes. Sleep deprivation and appetite control Sleep plays a vital role in regulating metabolism and appetite. When sleep deprived, the metabolic system will be out of balance, which will ultimately affect the dietary choices people make. Teens who are sleep deprived crave more carbohydrates. Sleep deprivation is a risk factor for obesity among young adults. There are two hormones, leptin and ghrelin, that are important in appetite control. Leptin, released by adipose tissue, is a hormone that inhibits appetite and increases energy expenditure. Ghrelin, released from the stomach, is a hormone that increases appetite and reduces energy expenditure. Sleep deprivation can cause a 19% decrease in the level of leptin. Subjects were deprived of sleep for 2 nights (4 hours per night) and got compensation of sleep for the next 2 nights (10 hours per night). Leptin levels decreased by 18% and ghrelin levels increased by 28%. There was an increase in hunger level by 23 which is probably due to the reduction leptin level. Subjects also preferred high carbohydrate foods (sweets, salty food and starchy food). Craving for salty food increased by 45%. Sleep deprivation can cause people to intake food for emotional/psychological need rather than caloric need of the body. Chronic sleep deprivation (less than 8 hours of sleep) was associated with increase in body mass index (BMI). In the Wisconsin sleep cohort study of 1024 patients, the shorter sleep durations showed reduced levels of leptin and elevated levels of ghrelin. In a study with 3000 patients, it has been found that men and women who sleep less than 5 hours have elevated body mass index (BMI). In another study that followed about 70.000 women for 16 years, there was a significant increase in body weight in those who slept 5 hours or less compared to those who slept 7–8 hours. As sleep time decreased over time from the 1950s to 2000s from about 8.5 hours to 6.5 hours, there has been an increase in the prevalence of obesity from about 10% to about 23%. References Sleep