Obesity Health Article

Definition

Obesity is an abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death.

Description

Obesity is defined by both the U.S. Department of Agriculture and the U.S. Department of Health and Human Services as the presence of a Body Mass Index (BMI) greater than or equal to 30. BMI is a measure of body weight relative to height and is computed as weight/height², where weight is measured in kilograms and height in meters. Obesity is considered a subset of overweight, which is indicated by a BMI of 25 or higher.

Approximately 55% of the U.S. population is overweight, and almost one in five is obese. Excessive weight can result in many serious, and potentially deadly, health problems, including hypertension, Type II diabetes mellitus (non-insulin dependent diabetes), increased risk for coronary disease, increased unexplained heart attack, hyperlipidemia, infertility, and a higher prevalence of colon, prostate, endometrial, and, possibly, breast cancer. Approximately 300,000 deaths a year are attributed to obesity, prompting leaders in public health, such as former Surgeon General C. Everett Koop, M.D., to label obesity "the second leading cause of preventable deaths in the United States."

Causes and symptoms

The mechanism for excessive weight gain is clear— more calories are consumed than the body burns, and the excess calories are stored as fat (adipose) tissue. However, the exact cause is not as clear and likely arises from a complex combination of factors.

Genetic factors significantly influence how the body regulates the appetite and the rate at which it turns food into energy (metabolic rate). Studies of adoptees confirm this relationship—the majority of adoptees followed a pattern of weight gain that more closely resembled that of their birth parents than their adoptive parents. Yet genetic factors do not explain the rapid increase in the prevalence of obesity in the U.S. and other industrialized countries in the past 10–15 years.

A genetic predisposition to weight gain, however, does not automatically mean that a person will be obese. Eating habits and patterns of physical activity also play a significant role in the amount of weight a person gains.

Recent studies have indicated that the amount of fat in a person's diet may have a greater impact on weight than the number of calories it contains. Carbohydrates (cereals, breads, fruits, and vegetables) and protein (fish, lean meat, turkey breast, skim milk) are converted to fuel almost as soon as they are consumed. Most fat calories are immediately stored in fat cells, which add to the body's weight and girth as they expand and multiply.

A sedentary life-style, particularly prevalent in affluent societies, such as in the United States, can contribute to weight gain. Psychological factors, such as depression and low self-esteem may, in some cases, also play a role in weight gain.

At what stage of life a person becomes obese can effect his or her ability to lose weight. Some studies suggest that during two critical periods of a person's life—in early childhood and puberty, excess calories are converted into new fat cells (hyperplastic obesity), while excess calories consumed in adulthood only serve to expand existing fat cells (hypertrophic obesity). Since dieting and exercise can only reduce the size of fat cells, not eliminate them, persons who were obese as children can have great difficulty losing weight, since they may have up to five times as many fat cells as someone who became over-weight as an adult. An estimated 13% of

children ages 6–11 years and 14% of adolescents ages 12–19 years are currently overweight.

Obesity can also be a side-effect of certain disorders and conditions, including Cushing's syndrome, a disorder involving the excessive release of the hormone cortisol; hypothyroidism, a condition caused by an underactive thyroid gland; neurologic disturbances, such as damage to the hypothalamus, a structure located deep within the brain that helps regulate appetite; and consumption of certain drugs, such as steroids or antidepressants.

The major symptoms of obesity are excessive weight gain and the presence of large amounts of fatty tissue. Obesity can also give rise to several secondary conditions, including arthritis and other orthopedic problems, such as lower back pain; heartburn; high cholesterol levels; high blood pressure; menstrual irregularities or cessation of menstruation (amenorrhea); shortness of breath that can be incapacitating; and skin disorders, arising from the bacterial breakdown of sweat and cellular material in thick folds of skin or from increased friction between folds.