The Global Epidemic of Obesity: Causes, Consequences, and Treatment

AADE Program Session
Thursday, August 12, 2004
10:00 AM - 11:30 AM

Obesity is a chronic disease of multiple etiologies characterized by the presence of excess adipose tissue. Of American adults, 65% are overweight and 31% are obese, and of American children, about 15% are obese. The US prevalence of obesity increased by two-fold in adults and three-fold in children over the last 25 years. There are 300,000 obesity-related deaths per year in the US. However, this country does not have the highest incidence of obesity. Other countries-even third-world countries-are fighting the disease. The incidence of obesity is 74.3% in Samoa, 41% in Kuwait, 35.7% in Paraguay, and 34% in the US. This contrasts with other countries such as China with a prevalence rate of 1.7%.

The increase in obesity was slow between 1960 and 1980. Since 1980, there has been an explosion of obesity worldwide. Explanations include reduced activity levels, greater access to food, a change in the character of food (eg, low-fat diets), fast food availability, increased TV access, computers in the workplace and home, and women working outside the home. However, the etiology of the epidemic is spotty, which suggests that these explanations seem insufficient. Obesity does not follow geographical or development patterns. For instance, between 1980 and 1995, obesity in England increased 150%, whereas obesity in Sweden increased 8% between 1980 and 1989 (Sweden's rising obesity rate is currently at about 16%.). These countries are similar in many respects, and explanations are not readily available to explain this disparity. The following etiologies should be considered as factors in obesity:

• Genetic factors
• Intrauterine, perinatal influences (malnutrition, hormonal influences, early life dietary influences)
• Environmental factors (diet, activity, drugs, stress, infection)
• Endocrine disease (rare)

Genetic factors are important-in fact, it seems some people are "destined" to be overweight. Pima Indians in Mexico, compared with Pimas in Arizona have a much higher BMI (30 for men, 35 for women in Arizona, 25 for Mexico Pimas). This demonstrates that both genetics and the environment have an influence on obesity. Intrauterine malnutrition can make those children more prone to obesity. What happens in utero aside from genetic makeup can influence weight later in life. Food plays a role, but it does not explain obesity in its entirety. Many drugs, including glucocorticoids and oral hypoglycemics (not metformin) including sulfonylureas and thiazolidinediones can increase body fat. Antidepressants, CNS agents can increase weight. If a patient starts new drug and starts to gain weight, the drug should be considered as a possible source. Stress can affect body weight. A number of papers have documented that children who have tonsillectomies gain more weight in the following year.

There is some evidence to suggest that obesity may be caused by an infectious agent. In animals, obesity has been shown to be linked to a number of infectious agents, including canine distemper virus, borna virus, and human adenoviruses AD-36 and AD-37. AD-36 increases adiposity and paradoxically decreases serum cholesterol and triglycerides in chickens, mice, and monkeys. Humans with antibodies to AD-36 are heavier and have lower serum cholesterol and triglycerides.

Complications of obesity are many and varied, including diabetes mellitus, hypertension, dyslipoproteinemia, cardiac disease, cerebrovascular disease, pulmonary disease, cancer, gallbladder disease, degenerative arthritis, venous statis, edema, GERD, urinary incontinence, reproductive dysfunction, gout, high intra-abdominal pressure, pseudotumor cerebri, adiposis dolorosa (area of painful subcutaneous fat, generally found in people with a BMI  of 30 and above), pregnancy risks, surgery risks, psychological disease, socioeconomic troubles, and premature mortality. Obesity also causes psychosocial complications caused by discrimination and injury to self-image.

Treatment components include diet, activity and exercise, lifestyle modification techniques, drugs, and surgery. Many diets have been tested over the years. Very low calorie diets (10-12 kcal/kg) seem successful and result in rapid weight loss and improvement of symptoms. There is a rapid regain of body weight after the diet ends, but studies show there is still a better long-term outcome in reducing blood glucose levels compared with a standard diet.

The rational for prescribing drugs for obesity is that obesity is chronic disease, and most chronic diseases are treated with drugs. Therapeutic agents include adrenergic agonists, combined adrenergic-serotonergic agonists, and malabsorptive agents. Surgery is another option for morbidly obese patients. Of the different types of gastric surgery to treat obesity, gastric bypass seems to best option. Of all weight-reducing strategies, gastric surgery is the most effective method of weight loss.