Sleep problems such as obstructive sleep apnea (airway obstruction during sleep, leading to disrupted sleep), insomnia, and inadequate sleep due to excessive work or partying promote obesity. Kristen Hairston from Wake Forest University School of Medicine in North Carolina and co-workers, in a five-year study, found that poor sleep habits in African-American and Hispanic young adults promoted gains in abdominal fat. Sleep duration was categorized as less than five hours, six to seven hours, or eight hours or more. In adults less than 40 years old, abdominal fat, organ fat (visceral fat), and body mass index (proportion of weight to height) increased in people getting too little or too much sleep (six to seven hours per night was best). Sleep duration was not related to changes in body fat in people over 40.
Source: Sleep, 33: 289-295