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Overview of Obesity

Facts about obesity

Overweight and obesity together make up a leading preventable cause of death in the U.S. Obesity is a chronic disease that can seriously affect your health.  

Overweight means that you have extra body weight, and obesity means having a high amount of extra body fat. Being overweight or obese raises your risk for health problems, including coronary heart disease, type 2 diabetes, and cancer.

Public health experts agree that overweight and obesity have reached epidemic proportions in this country and around the world, although the increase seems to have leveled off recently. More than a third of U.S. adults are obese. People ages 60 and older are more likely to be obese than younger adults, according to the most recent data from the National Health and Nutrition Examination Survey. And the problem also affects children. One out of five, or 17 percent, of U.S. children ages 6 to 19 is obese.

Who's obese?

Overweight and obesity are different points on a scale that ranges from being underweight to being morbidly obese. Where you fit on this scale is determined by your body mass index (BMI).

BMI is a measure of your weight as it relates to your height. BMI usually gives you a good idea of the amount of body fat you have. It's used by health care provider to find out your risk for obesity-related diseases. Occasionally, some very muscular people may have a BMI in the overweight range. But these people are not considered overweight because muscle tissue weighs more than fat tissue.

In general, a BMI from 18.5 to 24.9 in adults is considered normal. 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 stays about the same. His weight even drops slightly between ages 60 and 74. A woman's weight continues to increase until age 60, and then begins to drop.

Obesity can also be measured by waist-to-hip ratio. This is a measurement tool that looks at the amount of fat on your waist, compared with the amount of fat on your hips and buttocks. The waist circumference tells the amount of abdominal fat. A waist circumference of more than 40 inches in men and more than 35 inches in women may increase the risk for heart disease and other diseases tied to being overweight.

Talk with your health care provider if you have questions about healthy body weight.

What causes obesity?

In many ways, obesity is a puzzling disease. Experts don't know exactly how your body regulates your weight and body fat. What they do know is that a person who eats more calories than he or she uses for energy each day will gain weight.

But the risk factors that determine obesity can be complex. They are usually a combination of genes, socioeconomic factors, metabolism, and lifestyle choices. Some endocrine disorders, diseases, and medications may also affect a person's weight.

Factors that may affect obesity include:

  • Genetics. Studies show that the likelihood of becoming obese can be passed down through a family's genes. Researchers have found several genes that appear to be linked with obesity. Genes, for instance, may affect where you store extra fat in your body. But most researchers think that it takes more than just one gene to cause an obesity epidemic. They are continuing to do more research to better understand the how genes and lifestyle interact to cause obesity. Because families eat meals together and share other activities, environment also plays a role.

  • Metabolism factors. How your body uses energy is different from how another person's uses it. Metabolism and hormones can differ from person to person, and these factors play a role in how much weight you gain. One example is ghrelin, a hormone that regulates appetite. Researchers have found that ghrelin may help trigger hunger and give you a feeling of fullness. Another example is polycystic ovary syndrome (PCOS), a condition in women caused by high levels of certain hormones. A woman with PCOS is more likely to be obese.

  • Socioeconomic factors. How much money you make can affect whether you are obese. This is especially true for women. Women who are poor and of lower social status are more likely to be obese than women of higher socioeconomic status. This is especially true among minority groups.

  • Lifestyle choices. Overeating and a lack of exercise both contribute to obesity. But these are lifestyle choices that can be changed. If many of your calories come from refined foods or foods high in sugar or fat, you will likely gain weight. If you don't get much if any exercise, you'll find it hard to lose weight or maintain a healthy weight.

  • Medicines. Medicines like corticosteroids, antidepressants, and antiseizure drugs can cause you to gain weight.

  • Emotions. Emotional eating – eating when you're bored or upset – can lead to weight gain. Too little sleep. People who sleep fewer than five hours a night are more likely to become obese than people who get seven to eight hours of sleep a night.

Health effects of obesity

Obesity has a far-ranging negative effect on health. Each year in the U.S., obesity-related conditions cost more than $100 billion and cause premature deaths. The health effects linked with obesity include:

  • High blood pressure. Excess weight requires more blood to circulate to the fat tissue and the blood vessels to become narrow. This makes the heart work harder, because it must pump more blood against more resistance from the blood vessels. More circulating blood and more resistance also means more pressure on the artery walls. Higher pressure on the artery walls increases the blood pressure. Excess weight also raises blood cholesterol and triglyceride levels and lowers HDL ("good") cholesterol levels.

  • Type 2 diabetes. Obesity is the major cause of type 2 diabetes. Obesity can make your body resistant to insulin, the hormone that regulates blood sugar. When obesity causes insulin resistance, your blood sugar level rises. Even moderate obesity dramatically increases the risk for diabetes.

  • Heart disease. Atherosclerosis, or hardening of the arteries, happens more often in obese people. Coronary artery disease is also more common in obese people because fatty deposits build up in arteries that supply the heart. Narrowed arteries and reduced blood flow to the heart can cause chest pain called 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 extra weight stresses the joints. Joint replacement surgery may not be a good choice 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 causes people to stop breathing for brief periods during sleep. Sleep apnea interrupts sleep and causes sleepiness during the day. It also causes heavy snoring. Breathing problems tied to obesity happen when added weight of the chest wall squeezes the lungs. This restricts breathing. Sleep apnea is also linked with high blood pressure.

  • Cancer. Being overweight or obese increases your risk for a variety of cancers, according to the American Cancer Society. These include cancers of the colon and rectum, esophagus, kidney, and pancreas. Among obese women, the risk increases for cancer of the endometrium, or the lining of the uterus, and breast in those who have gone through menopause. Men who are overweight may have a higher risk for prostate cancer.

  • Metabolic syndrome. The National Cholesterol Education Program says that metabolic syndrome is risk factor for cardiovascular disease. Metabolic syndrome has of six major parts: abdominal obesity, high blood cholesterol, high blood pressure, insulin resistance, inflammation, and higher than normal levels of certain clotting chemicals in the blood. 

  • Psychosocial effects. People who are overweight or obese can have problems socially or psychologically. This is because the culture in the U.S. often values a body image that's overly thin. Overweight and obese people are often blamed for their condition. Other people may think of them as lazy or weak-willed. It is not uncommon for people who are overweight or obese to earn less than other people or to have fewer or no romantic relationships. Some people's disapproval of those who are overweight may progress to bias, discrimination, and even torment.