Copyright © 2009
by Daniel Matthew Korn

All Rights Reserved

When we think of stress, we often think of it as an emotion, what we feel when we cannot cope with what life throws at us. We think of stress as something that exists in our heads separate from our bodies, but this is not all that stress is. While we may experience stress as an emotion, our body experiences stress physically. During periods of stress and anxiety our adrenal glands produce a “fight or flight” hormone called cortisol.

This hormone is not just a result of the feeling of stress; it also causes the feeling of stress. Scientists have determined this by raising the level of cortisol in mice and observing their behavior. They have found that the mice experienced symptoms of anxiety and lowered reactions to outside stimuli. This is a sign of their nervous systems being overwhelmed and is typical of stress in humans.¹

Cortisol affects our entire body. It increases blood pressure and blood sugar, reduces the action of the immune system, slows bone formation, and more. All of these reactions might help us if we needed to escape from an attack or fend off a pack of predators, but they are of much less use to us today than when they originated.

Because of cortisol, chronic stress is associated with a wide range of health conditions. Chronic stress and chronically high cortisol levels can lower the body’s ability to resist infection. Stress is also thought to be the cause of many skin conditions, back pain, stomachaches, diarrhea, and, most interestingly for us, weight gain.

Soon after we get into a stressful situation, one of the things we usually want to do is eat. Imagine someone suddenly cuts you off in traffic and you have to brake immediately to avoid an accident. Your heart beats a little bit faster, you breathe a little bit more heavily, you feel angry, but you do not necessarily feel hungry immediately. This is because you have just released adrenaline, and adrenaline is an amphetamine. Like all amphetamines, in addition to making you awake and alert, it reduces your hunger.²

As a result of a stressful situation, your blood cortisol level also increases, and it stays elevated longer than your adrenaline level. Cortisol acts to help you recover from the effects of the situation in which you have just found yourself. Since raising your blood sugar, heart rate, and alert level likely caused you to use a lot of energy, one of the actions of the cortisol is to increase your hunger. While we may not always realize it because of the initial appetite suppression, after the initial stressor is over we eat more. This can be seen in laboratory experiments in which participants are exposed to stressful situations.³ It can also be seen in experiments in which participants have their blood cortisol levels and hunger levels measured at the same time.⁴ Stress leads to increased hunger, which leads to weight gain. Increased cortisol production is not only associated with weight gain, it is likely a cause of weight gain, as we can see from what happens to people who produce excess cortisol due to an abnormality in the adrenal glands.

Since the idea that stress leads to weight gain can be controversial, let us look at an example that occurs in nature. Cushing’s Syndrome, also called hypercorticism, is a hormonal disorder of very high cortisol levels in the blood. The cause of the disorder is an abnormality in the adrenal glands which causes an excess in cortisol production.⁵

The results of the high cortisol levels in Cushing’s Syndrome are what we would expect, based on the experiments performed on stress. Symptoms we would predict include increased hunger, rapid weight gain, and obesity. Other symptoms are psychological problems, acne, hypertension, high blood sugar, heart disease, and many more. Fortunately, effective treatments exist to control this disease. When cortisol production returns to normal, hunger and weight levels return to normal as well.

People, especially those at high latitudes, naturally tend to gain fat in the winter and lose it in the summer. While we are often aware of this by looking at our bathroom scales, this seasonal fluctuation can actually be more significant than we realize. We also tend to lose muscle in the winter and gain it in the summer. While we may notice that we have put on five pounds in the winter, we may actually have lost five pounds of muscle and gained ten pounds of fat.

When the body is functioning normally, our blood cortisol levels rise in the winter and fall in the summer, especially in latitudes with more severe winters. This is what is responsible for seasonal weight gain and loss, as well as seasonal mood changes. In people who are overweight, this seasonal cycle is disrupted, with higher levels year round, and especially high levels in the winter. The way the body determines the seasons is not entirely clear. There is some evidence that the clues are visual; in other words, the cycle may depend upon the amount of light that we see throughout the day at different times of the year.

There is also some evidence that vitamin D production plays a role. During the winter a type of ultraviolet light, UVB, is not present at higher latitudes. When this light hits the skin the body is able to manufacture vitamin D from cholesterol, the same substance from which the body manufactures cortisol. During the winter months, when UVB light is not present, vitamin D production drops and this may allow the body to create more cortisol.

This may be part of the reason why Hispanic-Americans have higher cortisol levels than non-Hispanic white Americans and are more likely to be overweight. Increased skin pigmentation blocks UVB rays, lowering vitamin D production, and may increase cortisol production On the other hand, decreased vitamin D production may also be a signal to the body that it is winter and it should put on weight through another mechanism. More research is needed before scientists have a definitive answer for what causes these changes. The body likely has more than one influence on its seasonal clock. What we know with certainty is that the seasons, ethnicity, and cortisol all play a role in weight regulation.^6,7

Cortisol’s effects on weight are reason enough to want to understand what can make our levels too high, but there is another reason. There is evidence raised cortisol levels increase aging. Every cell contains something called a telomere. A telomere is like a clock; every time a cell divides, a telomere becomes shorter. Shorter telomeres are linked to a range of diseases and aging. A study at the UCLA School of Medicine has shown that higher cortisol levels result in telomeres that become shorter faster. Thus, chronic stress, through its effect on cortisol, causes our cells to age faster.⁸

Since we have seen that excessive cortisol levels can cause weight gain by increasing hunger, to stay thin we need to keep our levels normal. This means avoiding stress. It is a cliché that modern life is stressful. Some of the common reasons given for stress are too many obligations, negative thoughts, working long hours, verbal abuse, and the fast pace of modern life.⁹

We can look at this list and say modern life is indeed very stressful, but why should it be more stressful than life several hundred years ago? In the early Americas, there were no two-day weekends. There was no concept of retirement, because people expected to work until they died. Deaths of both mother and baby were common in childbirth. The number one cause of death was infectious disease, and it was very common for parents to outlive their young children. Yet despite all of this, we still perceive modern life as more stressful than it used to be.

Since many of the things we normally think of as causing stress used to be more common than they are today, it is possible that the causes of heightened modern stress and increased weight gain are physiological rather than psychological. Stress is not just an emotion but a biological process associated with cortisol production. Excess cortisol can cause greater hunger and is the mechanism for weight gain from stress, seasonal changes, and Cushing’s Syndrome. While hunger is the most visible feature of weight gain, it cannot by itself explain the difficulty of weight loss.

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Citations:

² "Educating Students About Drug Use and Mental Health: Primary Grades Index." Centre for Addiction and Mental Health. 4/04/2009 http://www.camh.net/education/Resources_teachers_schools/Drug_Curriculum/Primary/curriculum_gr1to10glossary.html.

³ Jeanie Lerche Davis. "How You React to Stress May Affect How Your Clothes Fit." WebMD. 4/04/2009 http://www.webmd.com/news/20010116/how-you-react-to-stress-may-affect-how-your-clothes-fit.

⁴ Marci E. Gluck and others. "Cortisol, Hunger, and Desire to Binge Eat Following a Cold Stress Test in Obese Women with Binge Eating Disorder." Psychosomatic Medicine. 4/04/2009 http://www.psychosomaticmedicine.org/cgi/content/abstract/66/6/876.

⁵ "Cushing's Syndrome." National Endocrine and Metabolic Diseases Information Service. 4/04/2009 http://www.endocrine.niddk.nih.gov/pubs/cushings/cushings.htm#causes.

⁶ Matthew E. Levine, Albert N. Milliron, and Lawrence K. Duffy. "Diurnal and Seasonal Rhythms of Melatonin, Cortisol and Testosterone in Interior Alaska." Arctic Medical Research. 4/04/2009 http://www.milliron.net/sad/arcmedres94.htm.

⁷ "Obesity in Minority Populations." American Obesity Association. 4/04/2009 http://obesity1.tempdomainname.com/subs/fastfacts/Obesity_Minority_Pop.shtml.

⁸ Elaine Schmidt. "Study Identifies Mechanism Linking Stress to Physical Illness, Aging." UCLA Newsroom. 4/04/2009 http://newsroom.ucla.edu/portal/ucla/ucla-study-identifies-mechanism-53166.aspx?link_page_rss=53166.

⁹ Allan Schwartz. "Anxiety, Worry, and Stress, Oh My: The Bugaboos of Modern Life." Psych Central. 4/04/2009 http://psychcentral.com/lib/2006/anxiety-worry-and-stress-oh-my-the-bugaboos-of-modern-life/2/.