There is current research stating that there is a strong correlation between sleep deprivation and obesity. Sleep deprivation alters circulating levels of certain hormones which regulate hunger. For example, lack of sleep will increase levels of the hormone Ghrelin which will increase appetite, and will decrease levels of the hormone Leptin which will increase appetite as well. These hormonal shifts lead to increased hunger and preference for high calorie, high fat, and high sugar foods.
People with high Ghrelin and low Leptin have increased appetite, regardless of the persons' gender, BMI, eating and/or exercise habits. In a study called the "Obesity-Sleep Connection," results showed that sleeping less than 8 hours per night increased BMI. Subjects who slept 5 vs. 8 hours per night experienced a 14.9% increase in Ghrelin, and a 15.5% decrease in Leptin. In comparison to those who get 7-9 hours of sleep, those who get 6 hours of sleep are 23% more likely to be obese, those who get 5 hours of sleep are 50% more likely to obese, and those who get less than 4 hours of sleep are 73% more likely to be obese.
So what does this tell us? Start getting into bed earlier! If you combine a healthy diet, adequate exercise, and 8 hours of sleep, you are almost guaranteed to be at a healthy weight. So get cozy, close your eyes, and most importantly, lose the weight!