Obesity and Depression - Cause or Effect?

By Michele Hines, M.D.

An estimated 60 percent of Americans are overweight or obese and as many as 70 percent of them may be depressed. Depression and obesity are increasingly being recognized by physicians as co-morbid conditions - meaning that if you have one condition, you are likely to have the other.

But why? Does obesity cause depression? Or does depression cause obesity? If so, how?

Ask anyone, especially anyone who struggles with weight, why an obese person might be depressed, and you are likely to hear things like, "Being fat is depressing;" " I have low self-esteem;" " I'm fed up with discrimination and social pressures to be thin." There is truth in this. The psychological and social consequences of obesity can be devastating. But the real relationship between obesity and depression is more complex.

WHAT IS OBESITY?

Until recently, a person was considered obese if he or she was more than 20 percent over "ideal body weight." Currently, we use Body Mass Index ("BMI") to estimate body fat, rather than weight. A BMI of 25 to 29 is considered "overweight," while a BMI of 30 or greater is considered obese. Obesity is not a cosmetic issue, nor is it a character flaw. Obesity is a medical problem.

WHAT IS DEPRESSION?

The term "depression" refers to any of several mood disturbances sharing the symptoms of a depressed (sad, "blue") mood. There are often associated symptoms, such as decreased motivation and changes in appetite, sleep, energy and thinking. Carbohydrate craving, though not a diagnostic symptom of depression, can also be associated with it. Depression results from an imbalance in brain neurotransmitters (chemicals which carry signals between nerve cells) and is therefore considered to be a medical illness.

This information suggests that some individuals with neurotransmitter-related depression might become obese as a result of increased appetite and decreased energy expenditure - that is, more calories ingested than calories burned. In addition, some individuals who are psychologically predisposed to neurotransmitter-related depression tend to engage in excessive care taking of others, leaving little time or energy for their own exercise and nutrition. Finally, many (though not all) of the neurotransmitter-related medications used to treat depression can contribute to weight gain by increasing appetite, sleep, daytime sedation and possibly altering metabolism, as well.

In adolescents, the development of depression doubles the odds of becoming obese and increases the likelihood that obesity will persist into adulthood, especially in girls. In boys, however, chronic obesity increases the risk of developing depression. In depressed, obese adult women, successful weight loss lessens depression, but in adult men who are obese, the risk for depression may be lower than the risk in thin men - until medically complications develop, at which point, the risk for depression rises sharply. In both men and women with bipolar depression (previously called manic-depression), obese individuals tend to have more frequent depressive episodes than non-obese individuals, despite medication.

Neurotransmitters, such as serotonin, play a key role in both normal mood and brain function and the functioning of the digestive system. Some of the same neurotransmitters and hormones found in the gastrointestinal system are also found in the brain. This may explain why many of us experience "stomach" distress when we are stressed or emotionally upset. The popular term "gut feeling" arose from this common abdominal experience. Neurotransmitters and hormones also regulate fat cell metabolism, and the fat cells themselves secrete hormones, which ultimately influence appetite and metabolism by acting on the brain.

Physicians interested in treating obesity and depression use medications to alter neurotransmitter levels, ultimately affecting mood, appetite and metabolism. Stimulant medications, which increase energy, enhance mood and suppress appetite are an example. The newer mood-stabilizing medication topiramate successfully controls binges in obese individuals who suffer from binge eating disorder (wherein the individual loses control of food intake and consumes very large amounts of food in a short time) through its actions on neurotransmitters. Topiramate may also help improve depression in obese patients when combined with antidepressant medication.

Obesity carries an increased risk for the development of diseases other than depression, such as diabetes, cardiovascular disease and cancer. Metabolic syndrome, in which an individual suffers from dyslipidemia (imbalanced "good"/"bad" cholesterol and triglycerides), elevated blood pressure and glucose intolerance (an early warning sign of diabetes) appears to be a consequence of obesity and involves changes in the immune system.

Metabolic syndrome is much more likely to occur in obese women who have previously had depression than in those who have not. In obese men, depression has been linked to increased levels of C-reactive protein, an immune system chemical released by the body in response to an acute physiological stress. Increased levels of C-reactive protein are associated with coronary artery disease. These findings indicate that depression increases the risk of developing obesity-related disease complications, including heart disease and metabolic syndrome, probably via the effects of neurotransmitter imbalance on the immune system.

Does obesity cause depression? Or does depression cause obesity? And how? The answers are clearly "yes" to the first two questions, in the sense that each condition contributes to the other in many people. We have some answers to the question of how, but many of the details await the outcome of intensive research in the field of mind-body medicine.

THE BOTTOM LINE

If you are overweight or obese, lose weight now to prevent or improve co-morbid medical illnesses. If you are depressed, get treatment now, for the sake of both physical and mental health. If you are depressed and overweight or obese, seek treatment for both conditions. Your health is very much at risk, but safe and effective treatment is available.

Dr. Michelle Hines received her medical degree from Columbia University College of Physicians & Surgeons and completed her residency training in New York City . She is a Board-certified Psychiatrist and a member of the American Society of Bariatric Physicians. She has been in practice for 12 years and recently opened a new office in Louisville , where she specializes in the treatment of overweight & obesity.