Obesity and the Psychiatric Patient
abstract & commentary
Source: Devlin MJ, et al. Obesity: What mental health professionals need to know. Am J Psychiatry 2000;157:854-866.
Obesity is one of the most important medical conditions in U.S. society today, and patients with mental health problems are at particularly high risk of becoming overweight. Devlin and colleagues provide a useful survey of the vast field of obesity and its treatment. Writing a comprehensive yet concise review of obesity is challenging because of the many genetic and environmental factors contributing this complex and chronic illness.
Devlin et al first define some key terms and briefly review the epidemiology of obesity. One key concept is that of the body mass index (BMI). The BMI is defined as the ratio of the person’s weight (kg) to the square of the person’s height (m2). Normal weight is generally defined as a BMI less than 25 kg/m2, while "overweight" is defined as a BMI of 25-29.9 kg/m2. By convention, "obesity" is defined by a BMI of greater than 30 kg/m2. In the United States, more than half of the population is overweight, and of these, approximately one-half would be defined as obese. Minorities and persons living in poverty are affected at a disproportionately higher rate. Obesity is associated with excess mortality from many causes, particularly from cardiovascular disease, and the total amount of indirect and direct costs of obesity in the United States is estimated to be approximately $100 billion per year.
Certain neuropsychiatric illnesses seem to be associated with obesity, including major mood disorders, bulimia nervosa, personality disorders, binge eating disorders, sleep disorders, and many others.
There are also certainly genetic factors underlying obesity in many individuals, and animal models have produced some useful clues. The promise of harnessing leptin, brown fat, the beta-3 receptor, and many other molecules and systems remains encouraging. However, the human data so far are sparse and inconclusive, and the clinical application of genetics in obesity is likely years away. Moreover, reducing human obesity to a single gene or gene product is probably impossible due to the likely heterogeneity of the condition.
The concept of "set-point" was reviewed in detail. The set-point is the long-term stable weight for an individual, which is controlled by a number of known and unknown homeostatic mechanisms. Many obesity researchers believe the set-point is the major reason why the vast majority of obese patients who diet regain the lost weight over the longterm. Hereditary traits, smoking, exercise, and long-term nutritional habits are just some of the factors regulating the set-point. Obese children appear to have a better long-term outcome than adults after successful acute weight loss, suggesting a possible window of opportunity for set-point correction during childhood.
The important issue of psychotropic medication and obesity was superficially reviewed. Devlin et al note that many drugs within three of the four major classes of psychopharmacological agents are associated with obesity (benzodiazepines are the exception). Long-term treatment with the vast majority of antipsychotic agents (particularly the newer generation of atypical antipsychotic drugs) and mood stabilizers are frequently associated with weight gain. Among the antidepressants, the tricyclics, the monoamine oxidase inhibitors, and mirtazapine often cause weight gain. Devlin and colleagues note that the selective serotonin reuptake inhibitors (SSRIs) are often associated with a modest amount of weight loss acutely, with most patients regaining the lost weight in one year. They allude to the clinical observation of mild to moderate weight gain in some patients treated long term with SSRIs, despite experimental data to the contrary, where fluoxetine treatment for one year was not associated with weight gain. Due to widespread use of SSRIs and the consequent public health implications, weight gain associated with SSRIs merits much more study.
Comment by Andrew L. Stoll, MD
The treatment of obesity is big business and is a dynamic and growing field. No single weight loss method is effective in the majority of obese patients. Instead, a long-term multifaceted approach appears to offer the most benefit. The treatment of obesity can be divided into four major categories: behavioral weight control, pharmacotherapy, gastrointestinal surgery, and psychotherapy. Combining these methods as appropriate for an individual patient appears to be the best current approach. However, short-term treatment alone generally leads to a poor long-term outcome, and Devlin et al correctly point out that obesity should be actively treated over the longterm, as with any other chronic illness.
To summarize, obesity is one of the major public health problems in the world today. Finding the etiology, pathophysiology, and optimal treatment for obesity is an active area of research. The obvious financial bonanza to the inventor of a safe and effective weight loss treatment is a powerful incentive, which will hopefully yield results over the next few years.