What is 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).
The US Surgeon General has declared that overweight and obesity have reached epidemic proportions in this country. More than 9 million children between the ages of 6 and 19 are overweight. Public health officials say physical inactivity and poor diet are catching up to tobacco as a significant threat to health. Currently, about 34 percent of women and 27 percent of men are considered obese.
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.
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 that 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. One study published in 2004 found that 48 percent of children with overweight parents became overweight. Where a person carries weight—the hips or around the middle—is also strongly influenced by heredity.
- 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 six times more likely to be obese than women of higher socioeconomic status. The occurrence of obesity also is highest among minority groups, especially among women. Eighty-two percent of African-American women 20 years old or older are overweight.
- 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 American 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 more than $100 billion and cause an estimated 112,000 premature deaths in the U.S.
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 – In women, being overweight contributes to an increased risk for a variety of cancers including breast, colon, gallbladder and uterus cancers. Men who are overweight have a higher risk of colon and 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.
How is obesity diagnosed?
Obesity is generally diagnosed by a physician. It is determined by percentage of body fat and weight. Having a large percentage of body fat, regardless of how much you weigh, is unhealthy. You could be of normal weight or underweight and still have an unhealthy amount of body fat. Being overweight means that you have a heavy weight, but not necessarily too much body fat. For example, people who are muscular weigh more than those who are not; their extra weight comes from muscle, not body fat.
An assessment of whether you are overweight involves using three key measures:
- Body mass index (BMI)
- Waist circumference
- Risk factors for diseases and conditions associated with obesity, which include high blood pressure, high level of LDL (“bad”) cholesterol, high triglycerides, high blood sugar and smoking
Body mass index
The easiest way to find out whether you are overweight or obese involves determining your body mass index, or BMI. To calculate yours, click Get Started and complete the online health assessment. To determine if you are overweight or obese, compare your BMI to these ranges:
- A BMI of 18.4 or below = Underweight
- A BMI of 18.5 to 24.9 = Normal
- A BMI of 25 to 29.9 = Overweight
- A BMI of 30 or greater = Obese