HealthLifestyleObesitySleep DeprivationStress

The Role of Stress and Sleep in Obesity

Chronic stress, combined with positive energy balance (accumulation of body fat because energy is stored as fat), may cause an increased risk of obesity and other metabolic diseases like diabetes. The prevalence of obesity has increased dramatically in the US in the last several decades. The American Medical Association and the US Federal Drug Administration (FDA) have both reclassified obesity as a disease. Obesity is associated with type 2 diabetes, abnormally high fats including cholesterol and high blood pressure. This describes what doctors like to call the "Metabolic Syndrome." This cluster of abnormalities has insulin-resistance as the core cause.

Elements of our modern society may contribute to positive energy balance and the development of obesity and metabolic disease. These include our western diet (high in nutrients that cause inflammation), sedentary lifestyle and environmental stress. In fact, the prevalence of obesity is greater than 33% and metabolic syndrome is greater than 24%.

What is stress?

HPA-axis

Stress is any challenge to the natural homeostasis (normal state) of an organism, including man. We react to stress by producing a physiological stress response to regain our equilibrium (normal state). This stress response causes acute behavioral and physical adaptations. There is a change in the way we recognize things (cognition), lack of pain or feeling (analgesia), production of glucose from positive energy stores (called gluconeogenesis), breakdown of stored fat (lipolysis) to burn for energy and an inhibition to reproduce. There are two components of this stress response. The first is our automatic nervous system and the second is a series of "glands" that are associated with the hypothalamus (in the brain), pituitary gland (either stores hormones made in the hypothalamus or makes a number of hormones that the body uses) and the adrenal glands (sit on top of our kidneys and produce cortisol or cortisone) and is called the HPA axis.

What causes stress?

Stress can be caused by a number of things such as employment or social strains or even sleep deprivation. Short-term stress and our response to bring us back to normal does not cause obesity, but long-term stress can be harmful. In fact, long-term stress may cause a number of disease states. During the past 30 years, a number of studies have shown that obesity and other metabolic risk factors are associated with lower socioeconomic status, job strain, sleep deprivation and depression.

What can you do to reduce stress?

Remember, stress is a part of life, but you don't have to let it control you and your health. But because stress can affect your blood sugar and insulin levels as well as your cortisol levels, it's important to know what's causing it and take steps to deal with it. The following simple strategies can help:

  1. Keep a gratitude diary - At the end of the day, spend a few minutes writing about something you were grateful for in your day. Remembering this may help to raise your endorphins (happy hormones) and reduce stress.
  2. Spend time doing something you enjoy - Listen to music, or take a bath to relax or curl up with a good book. You can even work on a favorite hobby. Doing enjoyable things can reduce your stress level.
  3. Laugh - Laughter is one of the most effective ways to reduce stress.
  4. Learn to lean on family and friends - Studies have shown that most people are able to cope well with stress if they have strong social support networks with family, friends and even their pets.
  5. Don't be afraid to say "no" - This is a good way to reduce stress. When someone asks you to do something that's outside your comfort zone, don't be afraid to decline to do it. Know your limits. We can't do it all and you shouldn't feel guilty about it.
  6. Exercise - it doesn't have to be hardcore, but studies have shown that exercise can also increase your endorphins and reduce stress. Remember the expression "runner's high"? This is caused by an increase in your endorphin levels. Mild exercise can also do this.

Sleep and obesity

A good night’s sleep is one of the keys to good health, but may also be a key to maintaining a healthy weight. According to the Harvard School of Public Health, there is mounting evidence that people who get too little sleep have a higher risk of weight gain and obesity than people who get seven to eight hours of sleep a night. In 1998, 35 percent of American adults were getting 8 hours of sleep a night, but this dropped to 26 percent by 2005. Lack of sleep could be a major contributor to the obesity epidemic. This doesn't just apply to adults. Dozens of studies spanning five continents have looked at the link between sleep duration and obesity in children. Most (but not all) have found a convincing association between too little sleep and increased weight. The strongest evidence has come from studies that have tracked the sleep habits of large numbers of children over long periods of time (longitudinal studies), and have also adjusted for the many other factors that could increase children’s obesity risk, such as parents’ obesity, television time, and physical activity.

One study out of Britain followed more than 8,000 children from birth found that those who slept fewer than 10 and a half hours a night at age 3. They had a 45 percent higher risk of becoming obese by age 7, compared to children who slept more than 12 hours a night. Project Viva, a U.S. prospective cohort study of 915 children, found that infants who averaged fewer than 12 hours of sleep a day had twice the odds of being obese at age 3, compared with those who slept for 12 hours or more.  Maternal depression during pregnancy, introduction of solid foods before the age of 4 months, and infant TV viewing were all associated with shorter sleep duration.

The frightening part of a possible link between how many hours of sleep you get as a child and adult obesity is that childhood sleep habits may even have a long-term effect on weight, well into adulthood. Researchers in New Zealand followed 1,037 children from birth until age 32, collecting information from parents on the average number of hours their children slept at ages 5, 7, 9, and 11. They found that for each one hour reduction in sleep during childhood, there was an associated 50 percent higher risk of obesity at age 32.

Sleep and adult obesity

Most studies that measure adults’ sleep habits at one point in time (cross-sectional studies) have found a link between short sleep duration and obesity.  Longitudinal studies, though, can better answer questions about causality. The largest and longest study to date on adult sleep habits and weight is the Nurses’ Health Study, which followed 68,000 middle-age American women for up to 16 years.  Compared to women who slept seven hours a night, women who slept five hours or less were 15 percent more likely to become obese over the course of the study. A similar investigation in the Nurses’ Health Study and the Nurses’ Health Study II, a cohort of younger women, looked at the relationship between working a rotating night shift—an irregular schedule that mixes day and evening work with a few night shifts, throwing off circadian rhythms and impairing sleep—and risk of type 2 diabetes and obesity.  Researchers found that the longer women worked a rotating night shift, the greater their risk of developing diabetes and obesity.

So how does sleep affect body weight?

Researchers speculate that there are several ways that chronic sleep deprivation might lead to weight gain, either by increasing how much food people eat or decreasing the energy that they burn. Sleep deprivation could increase energy intake by:

    There may be an association between the number of hours you sleep and obesity
    There may be an association between the number of hours you sleep and obesity

  1. Increasing hunger - Sleep deprivation may alter the hormones that control hunger. (18) One found that young men who were deprived of sleep had higher levels of the appetite-stimulating hormone ghrelin and lower levels of the satiety-inducing hormone leptin. This resulted in a corresponding increase in hunger and appetite—especially for foods rich in fat and carbohydrates. 
  2. Giving people more time to eat - People who sleep less each night may eat more than people who get a full night’s sleep simply because they have more waking time available.  One small laboratory study found that people who were deprived of sleep and surrounded by tasty snacks tended to snack more, especially during the extra hours they were awake at night, than when they had adequate sleep. 
  3. Prompting people to choose less healthy diets - Observational studies have not seen a consistent link between sleep and food choices, but one study of Japanese workers did find that workers who slept fewer than six hours a night were more likely to eat out, have irregular meal patterns, and snack than those who slept more than six hours. 

Researchers speculate that there are several ways that chronic sleep deprivation might lead to weight gain, either by increasing how much food people eat or decreasing the energy that they burn. Sleep deprivation could increase energy intake by:

  1. Increasing hunger - Sleep deprivation may alter the hormones that control hunger. One found that young men who were deprived of sleep had higher levels of the appetite-stimulating hormone ghrelin and lower levels of the satiety-inducing hormone leptin. This resulted in a corresponding increase in hunger and appetite—especially for foods rich in fat and carbohydrates. 
  2. Giving people more time to eat - People who sleep less each night may eat more than people who get a full night’s sleep simply because they have more waking time available.  One small laboratory study found that people who were deprived of sleep and surrounded by tasty snacks tended to snack more, especially during the extra hours they were awake at night, than when they had adequate sleep. 
  3. Prompting people to choose less healthy diets - Observational studies have not seen a consistent link between sleep and food choices, but one study of Japanese workers did find that workers who slept fewer than six hours a night were more likely to eat out, have irregular meal patterns, and snack than those who slept more than six hours. 

Sleep deprivation could decrease energy expenditure

The following facts are known about sleep deprivation:

  1. Decreasing physical activity - People who don’t get enough sleep are more tired during the day. This may curb their physical activity.  Some studies have found that sleep-deprived people tend to spend more time watching TV, less time playing organized sports, and less time being physically active than people who get enough sleep. But these differences in physical activity or TV viewing are not large enough to explain the association between sleep and weight. 
  2. Lowering body temperature -  In laboratory experiments, people who are sleep-deprived tend to see a drop in their body temperatures, which in turn, may lead to decreased energy expenditure. Other studies did not find any link between sleep duration and total energy expenditure. 

Sleep is a promising target for obesity prevention

There is convincing evidence that getting a less than ideal amount of sleep is an independent and strong risk factor for obesity, in infants and children as well as in adults. Most of the research thus far, however, has consisted of observational studies. It remains to be seen whether teaching children or adults how to get a better night’s sleep can lower their risk of obesity or help them lose weight. There are randomized clinical trials currently underway that may soon provide more answers.

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