Causes and Symptoms
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Obesity is defined as a condition in which a person has accumulated so much adipose (fatty) tissue that his or her health is impaired. It is also defined by a person's body mass index (BMI) or waist measurement. The BMI is an indirect measurement of body fat. To calculate an adult's BMI in English measurements, multiply a person's weight in pounds by 703.1, and divide that number by the person's height in inches squared. A person with a BMI above 25 is considered overweight; a BMI over 30 is considered obese; and a BMI above 40 is considered morbid obesity. In terms of waist measurement, women with a waistline greater than 35 inches (88.9 centimeters) and men with a waistline greater than 40 inches (101.6 centimeters) are considered obese.
Some doctors think that obesity itself should be defined as a disease, while others maintain that it should be considered more broadly as an unhealthy condition that increases a person's risk of diabetes and other diseases.
Obesity is a condition that develops when a person takes in more food calories than his or her body burns up in the course of one's daily activities. The body turns those excess calories into fat. Overweight refers to an
excess of body weight compared to set standards. The extra weight may come from muscle, bone, fat, or body water. Obesity refers specifically to having an abnormally high proportion of body fat. Thus it is possible for an athlete to be overweight without being obese if his or her extra weight consists of muscle rather than fat tissue.
Obesity is a concern to doctors because it is associated with a number of diseases and disorders that can shorten a person's life expectancy as well as lower one's quality of life. Some of these diseases and other health problems include:
- Type 2 (adult-onset) diabetes
- High blood cholesterol levels
- Heart disease
- High blood pressure
- Sleep apnea
- Gallbladder disease
- Complications of pregnancy
- Increased risk of breast, colorectal, or kidney cancer
- Increased risk of complications following surgery
Obesity is a growing health problem in all countries in the developed world. The World Health Organization (WHO) estimated in 2005 that 10 percent of the world's population, or 400 million people, were obese, with another 760 million overweight. In the United States, about two-thirds of adults are overweight compared to the ideal weight for their sex, age, and height; one-third of American adults are obese. The proportion of obese adults in the general American population has more than doubled since 1960. Obesity costs the United States about $100 billion each year, $52 billion for direct health care costs and $33 billion for weight-loss products or programs.
Obesity is equally likely to affect men and women. There are, however, racial and ethnic differences within the American population. Groups that have a higher than average risk of obesity include the Pima Indians of Arizona and several other Native American tribes; Hispanics; African Americans; and Pacific Islanders.
Obesity is often associated with eating disorders in adults; about 30 percent of obese adults have a history of bulimia or binge eating.
Causes and Symptoms
Obesity is thought to be the end result of a combination of factors rather than having a single cause. Although obesity can be briefly described as an imbalance between food energy taken in and energy used up in exercise, eating and exercise are intertwined with other factors in complicated ways.
- Genetic factors. Researchers think that these account for 40–70 percent of the variations in human body size. Genetic factors affect how efficiently a person's body burns food and where on the body the excess fat is stored. People whose fat is stored around the abdomen have a higher risk of health problems than those whose extra weight is carried on the hips.
- Family environment. A person whose parents eat a lot of high-calorie foods is likely to adopt their eating habits.
- Age. People's bodies lose muscle tissue and gain fat as they age, and their calorie requirements drop; thus people who may not have been obese as young adults may become obese as they grow older.
- Sex. Men have more muscle tissue and less fat than women, and their calorie requirements for maintaining their body weight are higher than women's. Thus women are more likely than men of the same height and weight to gain weight if they consume the same number of calories as the men.
- Medical conditions. People with Cushing's syndrome, disorders of the thyroid gland, or depression are at increased risk of obesity.
- Medication side effects. People who must take corticosteroid drugs, antiseizure medications, or antidepressants may gain weight on these drugs.
- Emotional factors. Some people use food to soothe their feelings when they are sad, angry, bored, or upset.
- Quitting smoking. People who quit smoking often gain weight because food tastes better after they quit. In addition, the nicotine in tobacco raises the rate at which the body burns calories, so the former smoker's body needs fewer calories to maintain its weight.
- Pregnancy. Most women retain 4 to 6 pounds (1.8 to 2.7 kilograms) after each pregnancy; over time, these weight gains can lead to obesity.
The diagnosis of obesity in adults may be based on the CDC body mass index tables, or it may be based on other measurements. One common test involves measuring the thickness of the skin fold over the triceps muscle on the upper arm, although this measurement may not be accurate unless performed by a trained technician. Another test involves measuring the person's waist circumference at its widest point, usually at or just below the belly button.
Treatment of obesity is usually more complicated than simply placing people on a calorie-restricted diet or telling them to get more exercise. The doctor must take into account other health conditions that may affect the patients, their medications, occupation, and other lifestyle factors. For example, a person who lives alone can control food purchases or daily workouts more easily than someone who has to take the eating habits and time schedules of other family members into consideration. Similarly, someone with osteoarthritis may need to find forms of exercise that will not damage sore joints. In some cases the doctor and patient can work out a diet and exercise plan with the help of a registered dietitian or physical therapist, so that the patient can eat a nutritious diet that
includes one's favorite foods and find a form of exercise that he or she likes as well. One of the keys to sticking with a weight-loss program is satisfaction; people who feel deprived of the foods they like or bored by their physical exercise program are likely to quit.
It helps to remember that losing even a small amount of weight can be beneficial. Some doctors call this approach the “10 percent solution”—that is, losing just 10 percent of one's excess weight can lower the risk of heart disease and diabetes. If the person is able to keep that 10 percent weight loss for six months or longer, he or she can consider losing more weight.
People who have been unable to lose weight by a combination of exercise and food intake, or who are morbidly obese, may be treated by medications or weight-loss surgery. The two major medications that have been approved by the Food and Drug Administration (FDA) for weight loss are Meridia, which works by making the person feel full more quickly during a meal, and Xenical, which works by lowering the amount of fat that the body absorbs from the intestines. Both drugs have side effects, and weight loss tends to be modest, about 13 pounds (5.9 kilograms) in a year.
Weight-loss surgery, known as bariatric surgery, is usually limited to people with a BMI over 40 or those with a BMI over 35 combined with type 2 diabetes, sleep apnea, or heart disease. There are two basic types of surgery for weight loss, restrictive and malabsorptive. Restrictive procedures work by closing off part of the stomach so that the person cannot eat as much without feeling full. In malabsorptive procedures, the surgeon creates a bypass around the part of the small intestine where most of the calories in the food are absorbed. This type of surgery lowers the amount of calories that the body absorbs as well as lowering the patient's food intake. Bariatric surgery is not for everyone; it can produce serious complications that include bloating, nausea, and diarrhea. In addition, the patient will need to see the doctor periodically for the rest of his or her life.
According to the Centers for Disease Control and Prevention (CDC), obese adults have a 10–50 percent increase in their risk of dying from any cause, compared to people whose weight is normal or only slightly overweight. Obesity shortens a person's life expectancy by six to seven years on average, and accounts for 112,000 excess deaths each year in the United States compared to people of normal weight. Men with a BMI over 40 have their life expectancy shortened by twenty years, and women by five years.
Preventing weight gain or maintaining weight loss can be difficult in a society where inexpensive high-calorie snacks make it easy to overeat and television or video games make it easy to avoid physical activity. The following tips, however, can help a person stay committed to a weight-loss or weight-maintenance program:
- Make time each day—thirty to sixty minutes—for fast walking, swimming, or other forms of moderate exercise.
- Build a daily menu around fruits, vegetables, and whole-grain foods rather than sweets or snacks that are high in fat.
- Learn to recognize the situations or triggers that lead to overeating. One way to spot these patterns is to keep a food diary.
- If necessary, get help for depression or other psychological problems related to overeating.
- Keep track of weight and waist size on a regular basis.
It is likely that obesity will increase in the future, not just in the United States but worldwide. The World Health Organization (WHO) reported in 2006 that the only part of the world where obesity is still unusual is sub-Saharan Africa. Obesity is rising in all age groups, including the elderly, as well as in almost all countries.
WORDS TO KNOW
Adipose tissue : Fatty tissue.
Binge : An episode of eating in which a person consumes a larger amount of food within a limited period of time than most people would eat in similar circumstances.
Body mass index : BMI. An indirect measurement of the amount of body fat. The BMI of adults is calculated in English measurements by multiplying a person's weight in pounds by 703.1, and dividing that number by the person's height in inches squared.
Cushing syndrome : A disorder caused by the excess secretion of cortisol by the pituitary gland.
Ideal weight : Weight corresponding to the lowest death rate for individuals of a specific height, gender, and age.
Since the discovery in 1994 of leptin, a hormone that regulates the brain's sense that the body has had enough to eat, researchers are
studying it in hopes of learning more about the biological factors that influence appetite and food intake in humans. Other researchers are looking at the emotional and social factors that encourage people to overeat, and to test the effectiveness of psychotherapy as well as medications in weight-loss programs.
SEE ALSO Bulimia; Childhood obesity; Diabetes; Hypercholesterolemia; Hypertension; Sleep apnea
For more information
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