Does lack of sleep really effect weight loss?

Lack of Sleep
Studies find that the less people sleep, the more likely they are to be overweight or obese. People who report sleeping 5 hours a night, for example, are much more likely to become obese compared with people who sleep 7–8 hours a night.

People who sleep fewer hours also seem to prefer eating foods that are higher in calories and carbohydrates, which can lead to overeating, weight gain, and obesity over time.

Hormones that are released during sleep control appetite and the body's use of energy. For example, insulin controls the rise and fall of blood sugar levels during sleep. People who don't get enough sleep have insulin and blood sugar levels that are similar to those in people who are likely to have diabetes.

Also, people who don't get enough sleep regularly seem to have high levels of a hormone called ghrelin (which causes hunger) and low levels of a hormone called leptin (which normally helps curb hunger).

http://www.nhlbi.nih.gov/health/dci/Diseases/obe/obe_causes.html

Studies: Those Who Sleep Less Often Weigh More
How the hormones leptin and ghrelin set the stage for overeating was recently explored in two studies conducted at the University of Chicago in Illinois and at Stanford University in California.

In the Chicago study, doctors measured levels of leptin and ghrelin in 12 healthy men. They also noted their hunger and appetite levels. Soon after, the men were subjected to two days of sleep deprivation followed by two days of extended sleep. During this time doctors continued to monitor hormone levels, appetite, and activity.

The end result: When sleep was restricted, leptin levels went down and ghrelin levels went up. Not surprisingly, the men's appetite also increased proportionally. Their desire for high carbohydrate, calorie-dense foods increased by a whopping 45%.

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It was in the Stanford study, however, that the more provocative meaning of the leptin-ghrelin effect came to light. In this research -- a joint project between Stanford and the University of Wisconsin -- about 1,000 volunteers reported the number of hours they slept each night. Doctors then measured their levels of ghrelin and leptin, as well as charted their weight.

The result: Those who slept less than eight hours a night not only had lower levels of leptin and higher levels of ghrelin, but they also had a higher level of body fat. What's more, that level of body fat seemed to correlate with their sleep patterns. Specifically, those who slept the fewest hours per night weighed the most.

http://www.webmd.com/sleep-disorders/guide/lose-weight-while-sleeping?page=2