Stress and Weight Gain
The foods that we eat are metabolized by the body and stored as fats, carbohydrates and proteins. These energy stores cannot be used to provide fast energy for active muscles until they are broken down to glucose. This process is triggered by cortisol. Cortisol facilitates the breakdown of stored glucose (glycogen), fats, proteins and carbohydrates. It also counteracts the hormone insulin, which encourages cells to absorb and store glucose from the bloodstream. While all cells need insulin to absorb glucose and utilize it for energy, the muscles, however, can use glucose in the absence of insulin. Short-term stress usually does not trigger an increase in appetite for reasons discussed earlier. After an acute stress resolves, appetite is stimulated in an effort to replenish energy stores that were consumed during stress.
Appetite and Abdominal Fat
Chronic stress puts a tremendous strain on the body. The persistent release of cortisol can lead to continuous hunger because the body needs energy to fight or flee from a threat. However, when the glucose is not utilized to run or fight, the body stores the glucose as fat in the abdomen. In addition, elevated cortisol levels decrease thyroid hormone functioning which leads to weight gain. The effects of cortisol on the thyroid gland will be discussed in detail later. Chronic stress and elevated cortisol levels have been specifically linked to increased abdominal fat. Developing a beer belly may not seem to be any worse than thunder thighs. However, in fact, storage of fat around the abdomen is associated with a much higher risk of cardiovascular disease, stroke and heart attacks. Each individuals likelihood of developing abdominal fat varies according to genetics, diet, and lifestyle. These factors explain why some individuals tend to gain weight more easily around the midsection while others do not.
Very few of us are aware of the complex chemistry behind nervous eating. We just know that we tend to feel better after having a tasty slice of cake or a bag of chocolates. People under chronic stress tend to gravitate towards foods that are higher in salt, fat and sugar. Studies show that foods high in fat, sugar, or salt are, in fact, addictive. These types of food release opioids in the brain, which act like morphine to relieve stress and pain. We literally become food addicts, eating large amounts of junk foods even when we are not hungry.
The craving to eat food is a powerful survival mechanism that forces the body to eat what it desperately needs. Under prolonged stress, cortisol depletes the calming feel-good neurotransmitter serotonin, while increasing epinephrine levels. This combination of decreased serotonin and increased epinephrine causes depression and anxiety, respectively. Consuming carbohydrates increases serotonin by increasing insulin. When one eats comfort foods, glucose levels increase, which is followed by a rise in insulin. This rise in insulin leads to an increase in serotonin, which in turn, temporarily makes one feel better. Unfortunately, the rise in insulin subsequently leads to a decrease in glucose.
This decrease in glucose causes an increase in epinephrine because blood glucose drops. The decline in glucose causes a decrease in insulin. Serotonin, therefore, decreases and thus creates a vicious cycle of continuous carbohydrate craving to relieve the anxiety and depression associated with stress. Also, when stress is prolonged, the continuous production of cortisol causes the kidneys to excrete sodium, potassium, and magnesium. Consequently, sodium and potassium levels drop and the body develops an overwhelming desire to consume salt and salty foods.
Although it is not exactly known why some people react to stress by eating more and others react by losing their appetite, recent studies suggest that there is a complex interaction between stress, metabolism, and a change in eating behavior. Anxiety, depression, and altered brain metabolism have been linked to emotional overeating and under-eating. The chemical differences between individuals who stress eat and those who do not, appear to be higher levels of cortisol, insulin, glucose, and cholesterol in the bloodstream of stress eaters.
Stress is associated with insulin resistance because the body instinctively halts the storage of glucose, leading to high blood glucose levels. Glucose must be available to muscles if one is required to fight or flee. Cells are rendered insulin-resistant and, therefore, less sensitive to insulin. In the short run, insulin resistance is needed for the stress response, but in over the long term, it can be detrimental. The pancreas compensates for elevated glucose levels by increasing insulin production, which eventually leads to diabetes because the pancreas begins to fail. Glucose not used for the stress response under the influence of cortisol is stored as fat and leads to obesity. Obesity in turn leads to more insulin resistance.
Figure 1 illustrates that stress leads to insulin resistance, which in turn leads to elevated insulin levels and weight gain. Thus, a vicious cycle of insulin resistance, high insulin, and weight gain is seen with chronic stress.
Elevated levels of insulin also lead to inflammation of blood vessels and damaged to the lining of vessels. Inflammation is a stressor, which then compounds the initial stressor, which initiated the process. Damage to the lining of vessels associated with inflammation leads to cholesterol plaque formation to repair damage. Plaque formation produces a stiffening of the blood vessels, called atherosclerosis, which leads to hypertension and heart disease. The smaller vessels of the eyes, kidneys, and extremities are especially affected by elevated insulin levels and develop plaques. This excessive insulin and glucose leads to elevated cholesterol and triglyceride, which are associated with hypertension, heart disease, and diabetes. The combination of elevated insulin levels and homocysteine seen in stressed individuals greatly increases the risk of heart disease.
Metabolic syndrome refers to a syndrome that includes a combination of one or more symptoms listed below:
- Excess abdominal weight
- High blood pressure
- Low levels of HDL (good cholesterol)
- Abnormal levels of triglycerides
- High levels of blood glucose (pre-diabetes)
Metabolic syndrome is the result of insulin resistance and prolonged elevated insulin levels. When the pancreas is no longer able to produce enough insulin to maintain a normal glucose, the level of glucose in the blood rises leading to Type 2 or adult-onset diabetes. Type 1 diabetes is the result of the inability of the pancreas to produce insulin early in life, usually prior to age 20. Patients are often unaware that they have metabolic syndrome until late in the disease process. By the time the syndrome has progressed to diabetes or cardiovascular disease, it is much more difficult to treat. Metabolic syndrome has a genetic component; therefore, it is a good idea to be particularly vigilant if any close family member has diabetes or heart disease. As we have already mentioned, some individuals are more likely to respond to chronic stress by eating more. If you feel that you fall into this group, you should request blood tests during your next check-up to determine if fasting blood levels of insulin, glucose, triglycerides, and cholesterol are elevated. As you can see in the figure 23, insulin secretion increases years before fasting glucose becomes elevated. By the time that glucose is elevated, some irreversible damage may have occurred to the small vessels.
Certain cultural groups are also more likely to develop obesity and diabetes. They include Native Americans, Hispanic Americans, and African Americans; therefore, these groups should be monitored closely for metabolic syndrome.
Stress, Appetite, and Exercise
Several large studies have shown that losing only 6% of an individuals body weight can prevent 3 out of 5 cases of diabetes in younger individuals, and 70% of cases in older individuals. Lowering your sugar and carbohydrate intake, while at the same time burning your body’s glucose stores through exercise increases your body’s sensitivity to insulin.
Most of us know from experience that exercise reduces our stress levels and appetite. However, a new study suggests that not all exercise reduces appetite equally. University students who work out on a treadmill, a cardiovascular exercise, have much lower appetites than those who do other forms of exercise, such as weight lifting, a resistance exercise.
Several recent studies also show that even healthy individuals who are not at risk for either insulin resistance or metabolic syndrome, develop symptoms when exposed to chronic stress. In one study, 16 healthy male sailors in their 20s and 30s were followed over the course of a sailing competition. Initially, at the beginning of the race, the sailors overall weight dropped. However, as the competition progressed, they began to gain abdominal fat. They also were found to have high levels of insulin and triglycerides in their bloodstream. The researchers concluded that chronic stress over a period of three months led to measurable and significant biochemical changes in the metabolism of healthy individuals in spite of healthy diets and ample daily exercise. In conclusion, anyone with prolonged stress is at risk for developing excess abdominal fat, hypertension, insulin resistance, and vascular disease if undiagnosed and untreated.
Points to Remember
- Stress decreases serotonin levels, which may affect appetite and cause food craving.
- Cortisol makes most body cells resistant to the glucose storage affect of insulin.
- Stress causes insulin resistance and can lead to diabetes and obesity.
- Abdominal obesity is commonly associated with a prolonged stress response.
Be sure to pick up a copy of our book, The Stress Connection to better understand the affects of stress and elevated levels of the hormone, cortisol, on weight gain. We offer salivary cortisol testing to identify if abnormal cortisol levels could are contributing to your weight gain.
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