By KATHY SMITH
We spend about one-third of our lifetime sleeping. Sleep is important for learning and memory. Sleep also helps our immune system to resist illness and disease, increases response times in emergencies, improves our mood and feelings of wellness and gives us the energy we need to be more active and alert.
People today are sleeping fewer hours than their predecessors. In 1960, the National Sleep Foundation reported in a study that 40 percent of the adults slept between 8 and 9 hours a night. By 2002 that number had dropped to 23.5 percent. Obesity among adults nearly doubled over the same few decades. Research now demonstrates that sleep deprivation is a contributing factor to weight gain and obesity.
How does getting adequate sleep help prevent those extra pounds from adding up? Two words—ghrelin and leptin—also called “hunger hormones.”
The hormone ghrelin triggers hunger and stimulates appetite; increasing fat production and helping the body grow. This is good for infants and children, but not so good for adult dieters. Too much ghrelin stimulates overeating and inhibits weight loss, which may explain why dieters sometimes plateau while working to lose weight.
The hormone leptin signals satiety and lets us know it’s time to stop eating. Leptin levels are lowest while we sleep so we don’t wake up in the middle of the night feeling like we need to eat a big meal. With adequate sleep, ghrelin and leptin provide a valuable check and balance system for the body to help prevent overeating and obesity.
However, when sleep is lacking or inadequate, ghrelin levels rise, stimulating hunger and appetite, while leptin levels decrease, making you feel hungry even when you’ve eaten a full meal. When ghrelin and leptin run amok, the result is overeating, fat retention and obesity.
Studies also indicate that sleep-deprived individuals tend to crave foods that are high in carbohydrates such as breads, pastas, cakes and cookies. In a 2013 study conducted at the University of Colorado, 16 healthy people, restricted to fewer than five hours of sleep a night, consumed more calories through late-night snacking than they consumed at any meal during the day.