Overview of Obesity

Facts about obesity

Overweight and obesity together represent the second leading preventable cause of death in the United States. Obesity is a serious, chronic disease that can inflict substantial harm to a person’s health. Overweight and obesity are not the same; rather, they are different points on a continuum of weight ranging from being underweight to being morbidly obese. The percentage of people who fit into these two categories, overweight and obese, is determined by Body Mass Index (BMI).

Public health professionals agree that overweight and obesity have reached epidemic proportions in this country. Public health officials say physical inactivity and poor diet are catching up to tobacco as a significant threat to health. According to the most recent data from the 2009-2010 National Health and Nutrition Examination Survey, one out of five or 17 percent of U.S. children, ages 6 to 19, are obese. In addition, more than one third of the U.S. adult population is obese. Obesity prevalence did not differ between men and women; however, adults aged 60 and older were more likely to be obese than younger adults. From 2007-2008 and 2009-2010, the prevalence of obesity among adults and children did not change. 

BMI is a measure of weight proportionate to height. BMI is considered a useful measurement of the amount of body fat. Occasionally, some very muscular people may have a BMI in the overweight range. However, these people are not considered overweight because muscle tissue weighs more than fat tissue. Generally, BMI can be considered an effective way to evaluate whether a person is overweight or obese.

In adults, a BMI from 18.5 to 24.9 is considered normal while a BMI of more than 25 is considered overweight. A person is considered obese if the BMI is greater than 30 and morbidly obese if the BMI is 40 or greater. In general, after the age of 50, a man's weight stabilizes and even drops slightly between the ages of 60 and 74. However, a woman's weight continues to increase until age 60 and then begins to drop. When assessing a child's weight, the BMI is calculated and then plotted on a BMI for age percentile curve. The Centers for Disease Control and Prevention developed sex-specific BMI for age growth curves to account for a child's for body fat variances across ages and genders. Public health professionals classify a child overweight if his BMI for age percentile ranking is in the range of the 85th to less than the 95th percentile, or obese if his BMI for age percentile ranking is greater than the 95th percentile.

Another measure of obesity is the waist-to-hip ratio (WHR). The WHR is a measurement tool that looks at the proportion of fat stored on the waist, and hips and buttocks. The waist circumference indicates abdominal fat. A waist circumference over 40 inches in men and over 35 inches in women may increase the risk for heart disease and other diseases associated with being overweight.

Consult your doctor with questions regarding healthy body weight.

What causes obesity?

In many ways, obesity is a puzzling disease. How the body regulates weight and body fat is not well understood. On one hand, the cause appears to be simple in that if a person consumes more calories than he or she expends as energy, then he or she will gain weight.

However, the risk factors that determine obesity can be a complex combination of genetics, socioeconomic factors, metabolic factors, and lifestyle choices, as well as other factors. Some endocrine disorders, diseases, and medications may also exert a powerful influence on an individual's weight.

Factors which may influence the occurrence of obesity include, but are not limited to, the following:

• Genetics. Studies have shown that a predisposition toward obesity can be inherited. Although researchers have identified several genes that appear to be associated with obesity, most believe that one gene is not responsible for the entire obesity epidemic. The majority of current and future research aims to better understand the interaction between these gene variations and our ever-changing environment in the development of obesity.

• Metabolic factors. How a particular person expends energy is different from how someone else's body uses energy. Both metabolic and hormonal factors are not the same for everyone, but these factors play a role in determining weight gain. Recent studies show that levels of ghrelin, a peptide hormone known to regulate appetite, and other peptides in the stomach, play a role in triggering hunger and producing a feeling of fullness (satiety).

• Socioeconomic factors. There is a strong relationship between economic status and obesity, especially among women. Women who are poor and of lower social status are more likely to be obese than women of higher socioeconomic status. The occurrence of obesity is also highest among minority groups, especially among women.

• Lifestyle choices. Overeating, along with a sedentary lifestyle, contributes to obesity. These are lifestyle choices that can be affected by behavior change. Eating a diet in which a high percentage of calories come from sugary, high-fat, refined foods promotes weight gain. And, as more U.S. families eat on the go, high-calorie foods and beverages are often selected. Lack of regular exercise contributes to obesity in adults and makes it difficult to maintain weight loss. In children, inactivity, such as watching television or sitting at a computer, contributes to obesity.

Health effects of obesity

Obesity has a far-ranging negative effect on health. Each year obesity-related conditions cost over 100 billion dollars and cause premature deaths in the US. The health effects associated with obesity include, but are not limited to, the following:

• High blood pressure. Additional fat tissue in the body needs oxygen and nutrients in order to live, which requires the blood vessels to circulate more blood to the fat tissue. This increases the workload of the heart because it must pump more blood through additional blood vessels. More circulating blood also means more pressure on the artery walls. Higher pressure on the artery walls increases the blood pressure. In addition, extra weight can raise the heart rate and reduce the body's ability to transport blood through the vessels.

• Diabetes. Obesity is the major cause of type 2 diabetes. Obesity can cause resistance to insulin, the hormone that regulates blood sugar. When obesity causes insulin resistance, the blood sugar becomes elevated. Even moderate obesity dramatically increases the risk of diabetes.

• Heart disease. Atherosclerosis (hardening of the arteries) occurs more often in obese people compared to those who are not obese. Coronary artery disease is also more prevalent because fatty deposits build up in arteries that supply the heart. Narrowed arteries and reduced blood flow to the heart can cause chest pain (angina) or a heart attack. Blood clots can also form in narrowed arteries and cause a stroke.

• Joint problems, including osteoarthritis. Obesity can affect the knees and hips because of the stress placed on the joints by extra weight. Joint replacement surgery, while commonly performed on damaged joints, may not be an advisable option for an obese person because the artificial joint has a higher risk of loosening and causing further damage.

• Sleep apnea and respiratory problems. Sleep apnea, which causes people to stop breathing for brief periods, interrupts sleep throughout the night and causes sleepiness during the day. It also causes heavy snoring. Respiratory problems associated with obesity occur when added weight of the chest wall squeezes the lungs and causes restricted breathing. Sleep apnea is also associated with high blood pressure.

• Cancer. According to the American Cancer Society, being overweight contributes to an increased risk for a variety of cancers including breast (among postmenopausal women), colon and rectum, gallbladder, esophagus, kidney, pancreas, endometrium (lining of the uterus), and uterus. Men who are overweight have a higher risk of prostate cancers.

• Metabolic syndrome. The National Cholesterol Education Program has identified metabolic syndrome as a complex risk factor for cardiovascular disease. Metabolic syndrome consists of six major components: abdominal obesity, elevated blood cholesterol, elevated blood pressure, insulin resistance with or without glucose intolerance, elevation of certain blood components that indicate inflammation, and elevation of certain clotting factors in the blood. 

• Psychosocial effects. In a culture where often the ideal of physical attractiveness is to be overly thin, people who are overweight or obese frequently suffer disadvantages. Overweight and obese persons are often blamed for their condition and may be considered to be lazy or weak-willed. It is not uncommon for overweight or obese conditions to result in persons having lower incomes or having fewer or no romantic relationships. Disapproval of overweight persons expressed by some individuals may progress to bias, discrimination, and even torment.