In their now well-known 2008 study, Drs. Francesco P Cappuccio, Frances M. Taggart and Michelle A. Miller concluded that short sleepers (people who get less than five hours a night) are at an increased risk of obesity. That’s right, sleep less, weigh more.
The study showed two trends: that people of a healthy weight tended to sleep longer hours than those considered obese and that “a reduction of one hour of sleep per day would be associated with an… increase in BMI,” i.e., a you’ll gain weight if you lose sleep.
Fair enough, but why? What about our sleep habits relates to our weights?
Turns out, a whole lot.
The most obvious reasoning is that if you get less sleep at night, you’re more likely to be fatigued during the day and you won’t have the energy to exercise. But it’s not just fatigue that gets us. A 1999 University of Chicago study “found that building up a sleep debt over a matter of days can impair metabolism and disrupt hormone levels.”
In a 2005 Medscape article, Drs. Eva Van Cauter, et al. explained that “the regulation of leptin, a hormone released by the fat cells that signals satiety to the brain and thus suppresses appetite, is markedly dependent on sleep duration.” Bascially, the less you sleep, the less leptin you have in your system. If you don’t have enough leptin in your system, your body thinks its starving, even if you’ve been eating enough.
In a recent post, I talked about the circadian rhythm, which is the body’s natural 24-hour clock. In a 2011 study, Wenyu Huang, Kathryn Moynihan Ramsey and Joseph Bass concluded “that the circadian system is tightly coupled with processes controlling both sleep and metabolism,” and that “disruption of either the circadian clock or metabolism can lead to derangement of the other, thus predisposing to metabolic disorders such as obesity and type 2 diabetes.”
In laymen’s terms: mess with your natural sleep cycle (i.e., get too little sleep) and you mess with your metabolism, too.
So, what is enough sleep? Different studies give different numbers, but in general adults need between seven and eight hours and children need between 10 and 12 hours a night. Whether you want to look good on the beach this summer or if you just want to take care of your health, get to sleeping! Your waistline will thank you.