Really? They had to do a study to determine this? I could have told the researchers this. I usually do not choose fast food, but when I am too tired to cook, fast food suddenly becomes a convenient alternative. My will power to choose healthy foods also tends to decrease as my tiredness level increases. When I'm wide awake, I will choose the apple every time but when I'm tired, chocolate wins hands down. Sound familiar? However, evidence has shown that it may not be these food choices when tired that cause weight gain.
A 16 year study, which included 70,000 middle aged women, by the Case Western Reserve University showed that women who slept 5 hours per night were 32% more likely to experience major weight gain (33 pounds or more) over the course of the study compared to those who slept 7 hours per night.
The women reported their weight at the beginning of the study and then every 2 years there after. At the start of the study, women who slept 5 hours or less per night weighed an average of 5.4 pounds more than those sleeping 7 hours per night. They also gained an average of 1.6 pounds per year over the course of the study. One and a half pounds per year may not sound like much, but over 16 years, it adds up to 16 pounds!
The researchers looked at activity levels and the amount of food the women were eating to determine what was causing the weight gain. Exercise levels were about the same for those sleeping less than 5 hours and at least 7 hours. Those sleeping less must have been eating more, right? Wrong. "Prior studies have shown that after just a few days of sleep restriction, the hormones that control appetite cause people to become hungrier, so we thought that women who slept less might eat more, but, in fact, they ate less. That suggests that appetite and diet are not accounting for the weight gain in women who sleep less" states lead researcher Sanjay Patel, M.D.
A small study at the University of Chicago found that dieters getting at least 8.5 hours of sleep lost more body fat than those sleeping only 5.5 hours per night. When getting less sleep, participants burned more lean muscle mass instead of body fat. They were also hungrier and expended less energy, most likely to make up for not getting enough sleep.
Researchers are not sure why the amount of sleep you get affects your weight and whether your body burns fat or muscle but they do have some theories:
- Sleeping less may affect changes in a person's basal metabolic rate (the number of calories you burn when you rest).
- It could be that if you sleep less, you are more tired and move less leading to less calories being burned. This is not exercise-type movement, this is involuntary activity such as fidgeting, tapping fingers, nervous twitching, etc. Those little movements throughout the day add up.
- Sleep affects cortisol levels. Not getting enough sleep can cause the release of additional cortisol (the stress hormone) which has been linked to weight gain.
- Inadequate sleep interferes with the body's ability to metabolize carbohydrates and causes high blood levels of glucose. This leads to higher insulin levels and greater body-fat storage.
- Too little sleep drives down leptin (controls hunger) levels, which causes the body to crave carbohydrates. Carbohydrates themselves do not cause weight gain but if you are craving them, and eat too much, weight gain may happen.
I don't know about you, but I think I need to go to bed...
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