Sleep is more than just a pretty-making mechanism. While you get your beauty rest, your body is working away to regulate your systems and heal any damage done from daily wear and tear. More than the necessary mending, your digestive system is also pumping hard to process your food, metabolizing carbohydrates and breaking down fats. Some studies have linked sleep deprivation to weight problems, with the likely culprit being changes in hormone levels—cortisol and insulin in particular. Cortisol's main responsibility is the regulation of sugar, protein, fat, mineral and water metabolism. When physical or emotional stress throws us out of whack, cortisol reacts by pumping up the produced levels. Sleep deprivation also triggers cortisol production. Insulin is in charge of blood sugar and fat storage. Sleep deprivation has been linked to increased levels of insulin, which makes weight loss more challenging. Bottom line: unless you want your bottom to continue to expand, treat yourself to a good night sleep—nightly.