The Surprising Link Between Belly Fat And Sleep
I love talking to my readers, which is why I always invite you to contact me directly, whether it's via e-mail, Twitter or Facebook.
Last week I got an e-mail from a reader about an article he read on the Time magazine website.
"I read about a study that says my belly fat will increase if I don't get enough sleep," wrote MB. "Is this true? And if so, will sleeping more help me lose weight more quickly?"
The short answer is NO. Sleeping more, in and of itself, is not going to help you lose weight.
However, strange as it might sound, there's a growing body of evidence to show that better sleep habits are instrumental to the success of any weight loss plan.
Let me explain why...
Sleep
In the last 40 years, American adults have cut their average sleep time by nearly two hours. In 1960, U.S. adults slept an average of 8.5 hours a night. By 2002, that had fallen to less than seven hours a night.
Over the same period, the proportion of young adults sleeping less than seven hours more than doubled. Now, less than one out of four young adults sleeps at least eight hours a night.
And this lack of sleep appears to have a rather damaging effect on your waistline. Here's an extract from the Time article...
Sleeping fewer than five hours per night or more than eight hours per night was associated with higher concentrations of belly fat and increased body mass index (BMI) during the five-year study period compared with participants who slept six to seven hours per night. |
Although there are a number of studies showing a link between sleep deprivation and weight gain, the one I want to take a closer look at was published in the journal Sleep [3].
A team from the Mailman School of Public Health and the Obesity Research Center at Columbia analyzed data on 18,000 people aged between 32 and 59 who participated in the National Health and Nutrition Examination Survey during the 1980s.
Even after factors such as depression, physical activity, alcohol consumption, ethnicity, level of education, age and gender had been taken into account, people were more likely to be obese the less sleep they had.
While those who had less than four hours sleep were most at risk, people who got only five hours of sleep were 50% more likely to be obese than those who were getting a full night's rest.
"The results are somewhat counterintuitive," says lead author Dr. James Gangwisch, "since people who sleep less are naturally burning more calories."
"But we think it has more to do with what happens to your body when you deprive it of sleep as opposed to the amount of physical activity that you get."
And Dr. Stephen Heymsfield, who also worked on the study, says it was not as simple as saying that if people were awake for longer, they were likely to eat more.
"The metabolic regulatory system may have evolved to motivate humans to store fat during summer months when the nights are shorter and food is plentiful, which was a survival mechanism for the body to prepare for the dark winter months when food would not be as plentiful.
"As a result, sleeping less could serve as a trigger to the body to increase food intake and store fat."
Sleep deprivation appears to contribute to weight gain by disrupting the hormones that control your eating habits and metabolism. Specifically, sleep loss appears to have a big impact on a hormone called leptin.
Leptin
Named after leptos, the Greek term for "thin," leptin is a hormone released by your fat cells. Although it has a number of functions, one of leptin's main roles is to let your brain know how fat you are.
Leptin levels normally rise when you sleep. But during periods of sleep deprivation, low leptin levels tell the brain there is a shortage of food. The result is that you end up feeling VERY hungry.
In one trial, diabetes researcher Eve van Cauter and her research group investigated sleep deprivation's effects on leptin more closely [6].
The study involved 11 healthy 22-year-old men who spent 16 consecutive nights in the University of Chicago's sleep laboratory. For six days they got just four hours of sleep — their week of sleep deprivation.
The men's food and activity levels were strictly regulated and hormone levels were taken during the day and while they slept. Their sleep was also monitored to make sure they followed the study's guidelines.
Van Cauter's team measured circulating levels of leptin before the study, after two nights of only four hours in bed (average sleep time 3 hours and 49 minutes) and after two nights of 12 hours in bed (sleep time 9 hours and 3 minutes). They used questionnaires to assess hunger and the desire for different food types.
Subjects who slept only four hours a night had an 19% drop in leptin. As I mentioned earlier, when leptin levels are low, hunger tends to increase.
You can see the effect on leptin in the figure below, which shows the change in leptin levels over a 24-hour period after either 4 hours or 12 hours in bed.
The study volunteers also reported an increase in appetite, with a surge in desire for sweets, such as candy and cookies, salty foods such as chips and nuts, and starchy foods such as bread and pasta. Some volunteers were asking for up to 1,000 calories more per day.
"We don't yet know why food choice would shift," says Van Cauter. "Since the brain is fueled by glucose, we suspect it seeks simple carbohydrates when distressed by lack of sleep."
At the same time, the added difficulty of making decisions while sleepy may weaken your motivation to select more nutritious foods, making it harder to push away the doughnuts in favor of a low-fat yogurt.
"Our modern industrial society seems to have forgotten the importance of sleep," Van Cauter says.
"We are all under pressure to perform, in school, at work, in social and professional settings, and tempted by multiple diversions. There is a sense that you can pack in more of life by skimping on sleep. But we are finding that people tend to replace reduced sleep with added calories, and that's not a healthy trade."
If you're having trouble sleeping, and you've tried all the usual stuff like keeping your bedroom dark, avoiding caffeine in the evening, turning off the TV one hour before you go to bed and so forth, one alternative to sleeping pills (which can leave you feeling tired and groggy the next morning) is Valerian root.
Valerian, native to the Americas, Asia, and Europe has been used for thousands of years to ease insomnia, stress-related anxiety, and nervous restlessness.
Studies also show that Valerian reduces the time it takes to fall asleep. It also seems to improve the quality of sleep itself. Unlike many prescription sleep aids, Valerian has fewer effects the next day, such as morning drowsiness [5].
Personally, I've found that 2-3 capsules of Valerian root extract (the one I use is made by Solgar) is enough to help me sleep. If you do plan to use it, make sure to check for possible interactions with medications, as well as other precautions regarding its use.
So what's the bottom line here?
None of this means that sleeping for less than six hours each night is a guarantee that you'll gain weight. Nor does it mean that sleeping for longer will automatically cause you to lose weight.
What it DOES mean is that a lack of sleep is going to make it a lot harder to control your appetite, especially for high carbohydrate "junk foods" like sweets, cookies, and cakes.
And it's the subsequent increase in calorie intake, rather than the lack of sleep itself, that's responsible for any weight gain.
About The Author
 Christian Finn holds a master's degree in exercise science, is a certified personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Muscle & Fitness, Fit Pro, Zest and other popular fitness magazines.
If you're stuck
in a rut with your current exercise and diet plan... fed up with
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References
1. Plat, L., Leproult, R., L'Hermite-Baleriaux, M., Fery, F., Mockel, J., Polonsky, K.S., & Van Cauter, E. (1999). Metabolic effects of short-term elevations of plasma cortisol are more pronounced in the evening than in the morning. Journal of Clinical Endocrinology and Metabolism, 84, 3082-3092
2. Spiegel, K., Leproult, R., & Van Cauter, E. (1999). Impact of sleep debt on metabolic and endocrine function. Lancet, 354, 1435-1439
3. Gangwisch, J.E., Malaspina, D., Boden-Albala, B., & Heymsfield, S.B. (2005). Inadequate sleep as a risk factor for obesity: analyses of the NHANES I. Sleep, 28, 1289-1296
4. Vioque, J., Torres, A., & Quiles, J. (2000). Time spent watching television, sleep duration and obesity in adults living in Valencia, Spain. International Journal of Obesity and Related Metabolic Disorders, 24, 1683-1688
5. Donath, F., Quispe, S., Diefenbach, K., Maurer, A., Fietze, I., & Roots, I. (2000). Critical evaluation of the effect of valerian extract on sleep structure and sleep quality. Pharmacopsychiatry, 33, 47-53
6. Spiegel, K., Leproult, R., L'hermite-Baleriaux, M., Copinschi, G., Penev, P.D., & Van Cauter, E. (2004). Leptin levels are dependent on sleep duration: relationships with sympathovagal balance, carbohydrate regulation, cortisol, and thyrotropin. Journal of Clinical Endocrinology and Metabolism, 89, 5762-5771
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