In the 1960s people in the developed world slept 8-9 hours per night on average. In the 1990s, this had dropped to about 7 hours. Many now regularly sleep six hours or even less. What impact is this lack of sleep having on waistlines?
1. Regulatory hormones are impacted - metabolism is lower
Several studies have looked at the impact of fewer hours of sleep on hormonal patterns, metabolism and the immune system.
In one study, the subjects of the study slept for four hours per night for 6 nights and as a control, the same tests were undertaken following 6 nights of 12-hours of sleep per night.
Cortisol is higher in the sleep deprived (and the stressed out)
People who had been sleep deprived for six nights had six times more cortisol in their blood. The hormone cortisol is associated with the development of insulin resistance. Insulin resistance can lead to obesity and diabetes.
Less than one week of sleep deprivation can result in a young, healthy individual becoming pre-diabetic. The metabolic function that takes sugar out of the blood is reduced.
The body (liver and muscles) has a limit on the amount of glucose it can store as glycogen anyway.
Excess carbohydrates in your body are converted to and stored as fat. There is no limit on how many calories the body can store as fat (unfortunately).
Thyroid Stimulating Hormone is 30% lower and Growth Hormone higher in the sleep deprived
Lack of sleep leads to lower levels of the Thyroid Stimulating Hormone (TSH) and higher levels of Growth Hormone (GH). This combination increases weight gain.
GH has an anti-insulin effect.
2. Your brain loses its power to decide
This is also a hormonal impact that you cannot fight. During sleep, various regulatory hormones related to weight loss are released. If you're not sleeping enough you eat more because appetite-controlling hormones are suppressed.
Leptin lower (appetite suppressant)
The hormone leptin tells the brain when you have eaten enough. When you sleep less your body produces less leptin so the instruction telling your brain you are full is poor. Importantly, note that you also produce the same low levels of leptin after 3 days of eating less than 900 kcal! Do not eat too little.
Every hour of sleep lost is thought to lead to a 6% increase in leptin.
Ghrelin higher (appetite stimulant)
The hormone ghrelin stimulates your appetite. Studies show that people who are sleep-deprived have a higher level of ghrelin in their blood.
3. You eat more because you are awake
Okay, so why would you be awake when you should be sleeping anyway? You're either heavily overworked and still in the office or you're out having fun.
Have you noticed how it feels okay to comfort yourself with cake, biscuits and crisps when you are working late? Being overworked feels like punishment and the food seems to nullify the annoyance from being in the office when you would rather be at home.
If you're not at work, you might be in a bar, club or restaurant drinking your calories; or perhaps you are at the cinema throwing buttered or sugary popcorn down your gullet.
Whatever way you look at it, the more hours you are awake, the more time there is for eating.
The above said, note that another study involving 68,000 women found that women who slept less (less than 5hrs/night vs. 7+ hrs/night) were more likely to become obese even where they consumed fewer calories. This is likely due to the hormonal impact of poor sleep - lower metabolism.
4. Decreased exertion
When you feel tired you are not only less likely to take your scheduled exercise but you also fidget less. Yes, fidgeting does burn calories and the less of it you do, the less energy you are using up.
So far from being cool - regular sleeplessness can make you fat. I have to admit that before I acquired this knowledge I admired those who seemed not to need sleep. Of course, the impact of sleep loss is worse on some people than it is on others but let's face it, most of us need at least 8 hours of sleep to feel sane and some of us even need nine hours. I sleep 8 to 9 hours almost every night and I am not ashamed!
Medscape.org (registration to read articles is free)
National Center for Biotechnology Information
Although your personal finances and your business success are my primary interest, I believe you only operate at peak efficiency when you're fit and healthy. If you feel good, it filters through to your work. To help you with that, click for your free ebook: The Quick Guide to Sexy