For decades, researchers have suggested at least 8 hours of sleep per night, and there is a good reason behind this suggestion. When the human adult body sleeps less than 8 hours per night (even 6-7 hours) the body interprets this diminished sleep as stress. In response to stress, the adrenal gland produces cortisol, which increases blood glucose (sugar) levels, decreases bone formation, and suppresses the immune system. The imbalance in blood sugar levels induces cravings for junk food and sweets throughout the day, and can eventually lead to obesity, diabetes, heart disease, high blood pressure, mental distress, and stroke (according to the Centers for Disease Control and Prevention, CDC. Increased obesity correlated with decreased sleep for most regions surveyed in the United States. Cortisol has been associated with fat storage, and activates areas of the brain known as reward centers, that make you crave food. Additionally, reduced sleep causes an increase in the production of the hormone ghrelin and reduction of the hormone leptin. Since ghrelin causes the body to feel hungry and leptin causes the stomach to feel full, decreased leptin and increased ghrelin along with elevated cortisol levels is a diet disaster!
Having a busy week? Think that 3-4 nights of low sleep can hardly cause you any health issues? Well, think again! Research studies have shown that just 4 consecutive nights of reduced sleep can lead to 30% reduction in insulin sensitivity. So, while coffee, energy drinks, and munchies may keep you going throughout the day, your metabolism and organs are feeling the effects of sleep deprivation. When the body has normal insulin sensitivity, fat cells prevent excess storage of fat. However, when insulin sensitivity decreases (leading to insulin resistance), the body stores more fat, and produces more insulin. It then becomes a viscous cycle of weight gain, and often results in obesity and diabetes.
Therefore, sleep controls your diet! If you are aiming to lose weight or maintain a healthy body weight, getting adequate amounts of sleep is just as crucial as exercise. Some studies have even shown that getting 8 hours of sleep per night (as compared to only 4 hours) can help burn up to 5% more calories during the day (during periods of inactivity) and up to 20% more calories when digesting a meal. This is because the body refuels itself at night. If you compare your body to a car, you cannot refuel your car to only 50-70% (gasoline or electricity) and expect to get 100% output the following day; similarly, you cannot give yourself only 4-6 hours of sleep per night and expect to have the same amount of energy the next day as if you had slept 8 hours. Therefore, in order to maintain your daily routine (work and activity), after a night of low sleep, you feel the need to eat more in order to have the amount of output in productivity. The decreased energy will also cause you to reduce or eliminate your workout routine after a night of reduced sleep, because you are feeling sluggish.
In some ways, sleep deprivation leading to weight gain is very intuitive, such as the longer you are awake during the day, the more opportunities to increase your calorie intake, especially with late-night snacking. However, there are additional scientific studies to corroborate the reduced sleep and increased weight gain. Research studies have reported differences in brain activity in the pre-frontal cortex (our decision making brain center) for sleep deprived versus well-rested individuals. Therefore, during periods of low sleep, the brain has a much harder time of making good decisions, particularly about foods and exercise. So, in addition to making healthy food choices and fitting in exercise to your daily routine, remember that adequate sleep is just as important for your health and your diet!