| Obesity is an increase in body weight beyond the limitation of skeletal and physical requirements as the result of an excessive accumulation of fat in the body.
Most commonly, obesity occurs when energy intake (calories) exceeds energy use. Obesity can also occur as a result of disturbances in body hormones or certain genetic conditions. In these cases, the cause of the imbalance between energy intake and energy use remains unclear.
Simple obesity differs from morbid obesity. Morbidly obese individuals have a body weight that is 2, 3, or more, times the ideal weight and includes the state reached when the degree of obesity begins to interfere with normal physiological functions, such as breathing. Morbid obesity may lead to hypertension, diabetes, joint disease, and certain types of cancers.
The greater the obesity, the greater the risk of disease and death. Obesity as defined by a body mass index (BMI) of 30.0 to 34.9 kg/m2 carries a high-risk of disease. Individuals with a BMI of 35.0 to 39.9 kg/m2 are at very high-risk of disease, and those with a BMI of 40.0 or greater are at extremely high-risk (Klein 1619).Risk: Evidence suggests obesity often has more than one cause. Genetic, environmental, psychological, and other factors may play a part.
Obesity tends to run in families, which suggests a genetic cause. However, family members not only share genes but also diet and lifestyle habits that may contribute to obesity. An individual's environment includes lifestyle behaviors such as what he or she eats and the amount of activity expended. Americans tend to have high-fat diets because they often put taste and convenience ahead of nutritional content. Most Americans do not get enough exercise and often eat high-fat fast food.
In the US, more men than women are overweight, but more women than men meet the criteria for obesity. The proportion of men and women who are obese vary greatly according to ethnicity; black women are 80% more likely to be obese than black men. Mexican-American women are also more often obese than Mexican-American men. However, men in all ethnic groups are more likely to have abdominal obesity, which predisposes them to heart disease. Overall, the highest prevalence of overweight and obesity are found in black women and Mexican-American men and women. Obesity is most prevalent in adults aged 20 to 60 years, after which point it drops off considerably.
Obesity is most prevalent in the East South-Central US (21.2%) and least prevalent in the Mountain region (14.5%) (Zimmerman 229).
Many individuals eat in response to negative emotions, such as boredom, sadness, or anger. While most overweight individuals have no more psychological disturbance than normal-weight individuals, about 30% of those seeking treatment for serious weight problems have difficulties with binge eating. Research shows that binge eaters have more difficulty losing weight and keeping the weight off than individuals without binge eating problems.
Some rare illnesses can cause obesity, including hypothyroidism, Cushing's syndrome, depression, and certain neurologic problems. Certain drugs, such as steroids and some antidepressants, may cause excessive weight gain. Incidence and Prevalence: The prevalence of obesity (defined as a body mass index [BMI] of over 30) in the US has risen dramatically over the past several decades. Sixty-one percent (110 million) of individuals aged 20 to 74 years in the US are considered overweight (Klein 1625). US population surveys have shown that the prevalence of overweight increased from 30.5% to 34.0% and the prevalence of obesity more than doubled, from 12.8% to 27%, from 1960 to 2003; children and adolescents have also been dramatically affected, with 10% to 15% of children aged 6 to 17 years now classified as overweight (Klein 1625). Recent estimates attribute 300,000 deaths a year in the US to obesity, making it second only to cigarette smoking as a cause of death (Klein 1619). Worldwide, about 8.2% of the population is considered obese. The prevalence of obesity varies greatly throughout the world. According to the World Health Organization, the number of obese adults rose 50% from 1995 to 2000 to 300 million. |