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The link between sleep and weight loss

Looking to shed a few pounds? Try a good night's sleep.

(Photo: Buero Monaco/Getty)

Recent studies are connecting the dots between a good night’s sleep and weight loss. What these studies are helping make clear is that, by themselves, cutting calories and increasing physical activity won’t help everyone when it comes to fighting obesity. You need sleep, too.

According to an article (subscription required) in the September 18, 2012 issue of the Canadian Medical Association Journal, inadequate sleep influences body weight in a couple of ways. The referenced studies have found that people who don’t sleep well also tend to eat more at night, and that fatigue affects levels of key hormones that help the body regulate hunger.

The CMA findings support evidence my medical team has been gathering by encouraging our clients to take a hard look at their lifestyle, including how much sleep they get and the quality of their sleep. But apart from checking into a sleep lab, how can anyone monitor their own sleep in order to improve it? Fortunately, there’s an app for that.

At our clinic, we ask clients to measure their activity levels, dietary intake and sleep using a device we call the HealthETracker. Worn on an armband 24/7 for a few weeks it gives users a true picture of how many calories they’re burning and how much good sleep they’re actually getting. Results can be viewed online the results on line by plugging the tracker into a computer. The user can view a graph showing how many times she awoke during the night and her overall sleep efficiency rate.

Among our weight-loss-resistant clients, there was one common theme: their quantity and quality of sleep or sleep efficiency was low, generally in the 70% range, compared to the well-rested group at 90% or more. Once the sleep deprivation issue was rectified, hormone balance returned to more normal levels and weight began to come off like most of our other clients. For me, this is absolute clinical proof that sleep plays a critical role in curbing obesity.

Our findings echo an October 2010 study titled, “Insufficient sleep undermines dietary efforts to reduce adiposity” (subscription required) by the University of Chicago and published in the Annals of Internal Medicine. It compared results between one group of sleep lab participants who slept 5.5 hours and a second group, which got 8.5 hours of sleep every night in the lab for two weeks. Both groups cut their calorie intake by the same amount of calories. Those who slept longest lost more body fat and maintained more of their lean body mass than the shorter sleepers.

These results are likely because lack of sleep can mess with the body’s appetite-control mechanisms. The CMA article noted fatigue affects levels of key hormones— including cortisol, insulin and growth hormones—that help the body regulate hunger. The key point to be aware of is that when we are sleep deprived and tired, cortisol secretion increases. Your body will keep going if you insist, but there’s a cost.

Cortisol is usually released in response to stress, which: tells the body to conserve glucose for energy, thus preventing the glucose from feeding the brain, which negatively affects memory; generates new energy from stored reserves (causing muscle wasting); diverts energy away from low-priority activities (such as the immune system, which leads to more illness) in order to survive immediate threats or prepare for the exertion of a new day.

Cortisol also counteracts the effect of insulin which leads to an increase in blood sugar levels. The body thinks you need more blood sugar as a response to stress. And this in turn is why chronic stress has been known to lead to diabetes.

Finally, the growth hormone is critical to metabolism, healing and repair of bones and tissues. This hormone is regenerated each day during sleep. Insufficient sleep results in lower levels of growth. Your metabolism consequently slows down and your weight increases.

Both the CMA work and University of Chicago study mentioned here confirm what we’ve seen in practice at our clinic. We tell clients that as well as knowing hormone counts, it’s just as important to consider your lifestyle ‘counts’, especially your sleep efficiency level. Without peaceful sleep, some people may never lose those stubborn pounds.

Dr. Elaine Chin is founder of the Executive Health Centre.