The U.S. Surgeon General has declared that the number of people overweight and obese have reached epidemic proportions in this country. One in three U.S. adults are overweight or obese. Public health officials say physical inactivity and poor diet are catching up to tobacco as a significant threat to 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).
BMI stands for "Body Mass Index" a ratio between height and weight. It is a mathematical formula that correlates with body fat.
There is a certain group of people who should not use BMI as the basis for determining relative risk of disease.
- Competitive athletes and body builders. These people may have a high BMI due to a relatively larger amount of muscle.
- Women who are pregnant or breast feeding
- Growing children
- Frail and sedentary elderly individuals
Generally, BMI can be considered an effective way to evaluate whether a person is overweight or obese. There is a strong correlation between BMI and body fat percent. According to the National Heart, Lung, and Blood Institute (NHLBI), 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 their 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.
Excess body fat is never good for your health, but it is more harmful if it's up around the abdomen than if it is down in the hips and thighs. In other words, it is healthier to be shaped like a pear than an apple. A high waist circumference becomes an independent prediction of risk for developing certain diseases such as:
- Cardiovascular disease (heart disease)
- Dyslipidemia (high cholesterol, high triglycerides)
- Metabolic syndrome (overweight, high blood pressure, and high levels of cholesterol and blood sugar)
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:
- Genetics - Studies have shown that a predisposition toward obesity can be inherited. The chance of being overweight increases by 25 percent if one or both parents are obese. 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. Those who are poor and of lower social status are six times more likely to be obese than those of higher socioeconomic status. The occurrence of obesity is also highest among minority groups.
- 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 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 and cause an estimated 300,000 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. This type of diabetes begins in adulthood. 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) is present 10 times 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. 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. In the U.S., approximately one-third of overweight or obese individuals exhibit metabolic syndrome.
- Psychosocial effects - In a culture where often the ideal physical attractiveness is to be overly thin, people who are overweight or obese frequently suffer disadvantages. Overweight and obese individuals 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 individuals having lower incomes or having fewer or no romantic relationships. Unsuccessful attempts at dieting to lose weight can also lead to depression, which in itself can increase the risk of heart disease.