What Is Obesity?
Chapter 1
What Is Obesity?
Many people view obesity as a weakness of character or lack of willpower that allows individuals to eat so much they gain tremendous amounts of weight. Recently, however, an increasing number of experts are viewing obesity as a disease that affects millions of people, including children and teens.
According to the American Obesity Association, "When there is too much body fat, the result is obesity. Obesity is not a sign of a person being out of control. It is a serious medical disease that affects over a quarter of adults in the United States, and about 14% of children and adolescents. It is the second leading cause of preventable death after smoking."2
The association points out that obesity fits all the medical definitions of a disease, those definitions being "an interruption, cessation, or disorder of a bodily function, organ, or system."3 The disorder that characterizes obesity is an accumulation of excess fat and weight that occurs over time when a person takes in more calories than they expend. A calorie is a measure of heat. It is usually expressed as a kilocalorie, which is the amount of heat needed to raise the temperature of one kilogram of water one degree Celsius. In reference to food, a calorie measures the amount of energy the food gives the consumer as it passes through the body. The body uses calories to stay alive as well as for physical activity.
Overweight and Obese
The terms obese and overweight are often used interchangeably, but health experts point out that technically there is a difference. The term overweight refers to increased body weight relative to height based on some standard, such as the height-weight tables found in doctors' offices. People who are overweight may or may not have excess fat. Obesity is strictly defined as an excessive amount of body fat in relation to lean body mass. This category of disease is generally further broken down into subdivisions of mild, moderate, and morbid (or severe) obesity. The classifications are not strictly defined among medical experts, but usually morbid obesity means that an individual is at least one hundred pounds over their ideal weight and is likely to develop major medical or physical problems related to the condition. The other categories may vary on the basis of body-fat distribution, age, number of pounds overweight, degree of medical risk, and degree of control an individual has over eating. Different doctors tend to focus on different aspects of these values in defining individual cases. For example, since researchers have determined that excess fat in the abdomen is medically more risky than excess fat in the hips or legs, a doctor is more likely to classify someone with a lot of excess abdominal fat as moderately or severely obese because of the risk factor.
The measurement most commonly used to differentiate between being obese and being overweight is the body mass index (BMI) This is a number that indicates body weight relative to height. The formula for BMI is the weight in pounds divided by the height in inches squared, times 703. For example, someone who is six foot three inches tall and weighs 220 pounds has a BMI of 27.5. BMI can also be calculated using kilograms and meters. This formula is the weight in kilograms divided by the height in meters squared, times ten thousand. BMI below 18.5 is considered underweight, between 18.5 and 24.9 is considered normal, between 25 and 29.9 is overweight, over 30 is obese, and over 40 is morbidly obese.
Other Measurements
Although BMI is most commonly employed to determine whether someone is overweight or obese, there are other indices used to calculate these conditions. Doctors often use insurance-company-generated height-weight tables to make this assessment. These tables list a range of acceptable weights for people of a particular height, body frame, and gender. This ends up allowing a fairly wide range of weights for people of the same height, depending on whether their body frame is large, medium, or small. For example, according to the tables published by one insurance company, a man six feet tall with a small frame ideally weighs between 149 and 160 pounds. A man of this height with a medium frame should weigh between 157 and 170 pounds and one with a large frame between 164 and 188 pounds. Someone who weighs more than these specified ranges is considered to be overweight or obese, depending on how much over they are.
Another measurement sometimes used to gauge obesity and its related health risks is the waist circumference measurement. This value is taken to determine whether the amount of abdominal fat is sufficient to put someone at risk of developing type 2 diabetes, high blood pressure, or cardiovascular disease. If a man has a waist circumference of forty inches or more and a woman has one that is thirty-five inches or more, and their BMI is higher than twenty-five, they are considered at increased risk.
The waist-to-hip ratio is another measurement sometimes used to gauge obesity. This is the ratio of a person's waist circumference to hip circumference. A waist-to-hip ratio of one or higher is considered risky for the development of heart disease. A waist-to-hip ratio of .90 or less is considered safe for men and .80 or less is considered safe for women.
Many physicians believe that simply measuring inches, weight, and height and plugging these values into a formula does not give a true assessment of whether someone is overweight, obese, or at risk for various medical problems, so they employ techniques that directly measure fat content of the body. These methods are known as anthropometry. Some anthropometry techniques use instruments called calipers to measure the thickness of skin folds in various places on the body. These methods operate under the assumption that the thickness of the skin folds represents the fatness of the entire body.
Other ways of measuring body-fat content include underwater weighing and bioelectric impedance analysis (BIA). Underwater weighing weighs the person in water to calculate body density. It yields a measurement of the percent of body fat relative to weight. With BIA, a small electrical current is run throughout the body and its resistance is measured at various points to assess fat content. Lean body tissue conducts electricity to a greater degree than fat does. Therefore, by measuring how much electrical current a particular body conducts, doctors can tell how much fat the person has.
There are also several new, high-tech ways of measuring body fat. These include dual-energy X-ray absorptiometry (DXA), total body electrical conductivity (TOBEC), and near-infrared interactance (NIR). DXA instruments use two intensities of X-rays to differentiate between lean soft tissue, fat soft tissue, and bone. TOBEC measures body composition through the use of an electromagnetic field. Measurements in TOBEC are done by inserting the person into a tubular device containing coiled wire. When electricity passes through the wire, it sends a mild current through the individual. The device measures how much electricity the body conducts. NIR uses an infrared light wand to determine fat content and is based on the principles of light absorption and reflection. The light wand sends a low-energy beam of near-infrared light through the biceps muscle in the upper arm. Depending on how much fat and muscle are present in the biceps, the light is reflected or absorbed in differing amounts. A detector in the wand measures how much light is emitted after it passes through the biceps. This value is then plugged into a formula to calculate the percentage of body fat. All of these methods are considered reliable indications of body-fat content.
The Bottom Line
Whichever measurements are used to calculate being overweight and obese, experts say that as of 2003 in the United States there are about 127 million overweight adults, about 60 million obese adults, and about 9 million morbidly obese adults. These numbers have never been higher, and they continue to grow each year. In general, women are more likely to be obese than men, and people in lower socioeconomic groups are seven times more likely to be obese than those in higher socioeconomic groups. Education level also appears to play a role, as those with less education are more likely to be obese or overweight.
Race and ethnicity also play a role in obesity. African Americans, American Indians, and Hispanic Americans have a higher rate of obesity than do Caucasian Americans, and Asian Americans have a lower prevalence of obesity. African American and Hispanic American women with low incomes seem to be at highest risk for obesity. Americans of English, Scottish, and Irish descent tend to have a lower risk of obesity than do those descended from eastern and southern European countries. Experts believe this is probably due to genetic as well as lifestyle factors.
In other places in the world, the incidence of being over-weight and obese varies among particular groups. However, it is also at an all-time high, though the definition of these terms may vary among different cultures. While being overweight or obese in the United States is generally viewed as undesirable because of perceived standards of beauty that equate thinness with attractiveness, and because of concerns about the effects of obesity on health, in other cultures, this may not be the case. Medical experts in certain cultures may not perceive obesity to be a condition that warrants concern. In the Efik tribe of Nigeria, for instance, fatness is seen as beautiful. Young girls in this society are housed in fattening huts for up to two years before they marry to make them as beautiful as possible. The future husband provides the best foods available for his future bride. In New Guinea, men who are leaders are admired for their large body size. In the Bemba tribe in South Africa, obese men are seen as being economically successful and possessing the spiritual powers to withstand sorcerers' attacks, so obesity is considered positive there too.
Health Problems and Obesity
Even among cultures where obesity is seen as desirable, there is increasing evidence linking it to a variety of serious health problems. In the United States, such medical problems have been well documented, and experts know that obesity causes over three hundred thousand preventable deaths each year and accounts for over $100 billion in annual medical costs. According to the Centers for Disease Control and Prevention, "Although our society has made great strides in reducing other threats to health such as smoking, we have been unable to stem the rising tide of obesity in the population. This trend is particularly disturbing because obesity is central to the development of many chronic diseases such as type 2 diabetes, heart disease, hypertension, and cancer."4
Type 2 Diabetes
Type 2 diabetes mellitus, a disease in which the body is not able to properly metabolize sugar, is one of the most common ailments to affect overweight and obese people. It was once considered strictly an adult disease, but now many obese children and adolescents are affected too. Health experts are especially concerned about this trend because diabetes can lead to many serious complications, such as blindness, limb amputation, and kidney disease, and the longer someone has the disease, the higher the risk of these complications.
Type 2 diabetes is three to five times more prevalent among obese persons than in those of normal weight. The tendency to develop it increases the heavier the individual gets. Unlike in type 1 diabetes where the pancreas does not produce insulin, in type 2 diabetes, the pancreas does manufacture insulin. However, the body becomes resistant to the insulin, so the person must either inject additional synthetic insulin or take oral medication to allow the body to use whatever insulin is being produced.
Insulin is a hormone that is essential for allowing cells to take up glucose, the form of sugar that nourishes cells, from the bloodstream. Without insulin, these cells starve and glucose builds up in the blood, eventually leading to a diabetic coma and death unless treated.
Even when someone with diabetes takes medicine, fluctuations in blood-sugar levels often damage blood vessels and nerves and lead to eye, kidney, blood vessel, and nerve complications. Experts say that many obese people with type 2 diabetes would improve or even be cured of the condition if they would simply lose weight.
High Blood Pressure and Heart Disease
Being overweight or obese also commonly causes high blood pressure and heart disease. Blood pressure results from the heart pumping blood to the arteries. The pressure is the force of the blood pushing against the walls of these arteries. It is highest each time the heart beats and pumps blood and lowest when the heart is at rest between beats. Measuring this pressure is done with an instrument called a sphygmomanometer. A nurse or doctor wraps a blood-pressure cuff around the patient's upper arm and inflates the cuff with air to stop the blood flow for a few seconds. Then they open a valve on the sphygmomanometer to release air from the cuff and listen through a stethoscope to the sounds of the blood rushing through the artery.
The first sound heard and registered on the mercury column gauge of the instrument is the systolic pressure. This is the highest pressure and occurs as the blood begins to flow when the heart pumps. The second sound is the diastolic pressure, the lowest pressure, which occurs when the heart rests between beats. Blood-pressure readings are expressed as two numbers—the systolic over the diastolic pressure—and is measured in millimeters of mercury. A reading of 120/80 or less is considered good. Any reading above 140/90 is classified as high.
When blood pressure is high, the heart must work harder than normal, which makes it weaken and enlarge. This can lead to congestive heart failure, a condition where the heart can no longer pump the way it is supposed to. Uncontrolled high blood pressure can also cause the arteries to age faster than usual and to become hardened and scarred. Damaged arteries are not able to supply enough blood to organs throughout the body, and these organs may stop working properly. The kidneys, heart, and brain are especially vulnerable to damage from high blood pressure. Strokes resulting from impaired blood flow to the brain, heart attacks from blocked flow to the heart, and kidney failure from kidney artery damage are common complications. High blood pressure can be controlled with medication, but sometimes all that is necessary to lower it is for the individual to lose weight.
Besides the risk of heart disease from high blood pressure, obese people also run a much increased risk of heart disease due to high blood-fat levels. These blood fats consist of triglycerides and cholesterol. Both are produced by the liver and circulated in the blood. Triglycerides are fats that are normally elevated in the blood after digestion of fats in the intestine. But when the level of triglycerides stays elevated, this can contribute to heart disease. Cholesterol is a fat that is essential as a building material for cells in the body. But too much of it can clog the arteries, resulting in impaired circulation, chest pain, heart attack, stroke, and even sudden death. Experts point out that many of the effects of obesity and high blood-fat levels on cardiovascular health begin in childhood and progress to severe disease in adulthood. But even when someone becomes obese as an adult, heart disease is a major threat that is responsible for death in many such individuals.
Obesity and Cancer
In the late 1900s, medical science determined that obesity contributes to many forms of cancer. Cancer refers to a variety of conditions where unregulated cancer-cell growth kills the host organism unless successfully treated. A study published in 2003 by the New England Journal of Medicine in which scientists spent fifteen years evaluating nearly 1 million people concluded that excess weight contributes to more than ninety thousand cancer deaths in the United States each year. Earlier studies showed that being overweight or obese contributed to breast, uterus, colon, rectum, kidney, esophagus, and gall bladder cancers. The new study also linked being overweight or obese to cancers of the cervix, ovaries, pancreas, liver, stomach, and prostate, as well as multiple myeloma and non-Hodgkin's lymphoma.
The researchers say that having too much fat can contribute to cancer in several ways. Since excess fat increases the amount of the female hormone estrogen in the blood, it puts women at increased risk for cancers in the female reproductive system, including the breasts, ovaries, and uterus.
Excess fat also increases the risk of acid reflux, a condition in which stomach acid spews up into the esophagus thereby increasing the risk of cancer of the esophagus. Excess fat also raises levels of insulin in the body, since more insulin is produced to process excessive amounts of food, and this in turn stimulates cell growth. This can contribute to the out-of-control growth that characterizes cancer cells. Insulin can also contribute to cancer in another way; the insulin resistance that afflicts many obese people has been linked to cancers of the colon, rectum, breast, and pancreas. Another way that obesity can trigger cancer is by impairing the immune system. This makes the person less able to defend against cancer and other invading organisms.
Doctors point out that obesity makes cancers harder to diagnose, since many forms of cancer present themselves as lumps or bumps that cannot be seen in obese people. Diagnostic tests like MRIs (magnetic resonance imaging) are difficult to perform on obese people. This is because an MRI requires placement in a narrow, cylindrical, imaging device, and many obese people simply will not fit.
Obesity makes cancers more difficult to treat, since it is harder to operate on an obese person or to fit them into radiation-therapy machines. It also makes it harder for a physician to gauge chemotherapy dosages, since fat can absorb these medications. So not only does obesity contribute to a greater risk of many types of cancer, obese people who actually get cancer have less chance of being treated successfully.
Other Health Problems
Obesity is associated with many other health problems that can be life threatening, painful, or otherwise impair normal functioning. All kinds of pain, particularly that associated with the joints, bones, muscles, and feet, are much more common among obese people. Arthritis, a variety of conditions where the body attacks its own tissue resulting in pain and disability, is very common because the entire body is under extra strain due to the excessive weight. The hips, back, knees, and feet are most often affected by this process. The wrists and hands can also be impacted; experts report that carpal tunnel syndrome, a condition where the carpal tunnel in the wrist becomes inflamed, has a higher prevalence among obese people.
Other conditions that are more common in obese people include leg ulcers, blood clots, hernias, inflammation of the pancreas, infertility, menstrual disorders, increased infections due to poor circulation and a less efficient immune system, complications from pregnancy, increased birth defects in offspring, certain psychiatric disorders such as depression, daytime sleepiness and fatigue, gout (a painful condition that results from the deposit of uric acid crystals in joints), gallstones (that result from chunks of cholesterol building up in the gallbladder), and respiratory (or breathing) problems. Respiratory problems can consist simply of shortness of breath or may progress to the point that the person needs an oxygen tank to breathe at all. This is because the lungs of obese people do not work properly due to the strain placed on them. Under the burden of having so much fat in the chest muscles, the lungs cannot expand and take in oxygen in a normal manner, and this results in an abnormally low amount of oxygen in the blood. Other respiratory conditions commonly associated with obesity are asthma, where the airways constrict so as not to allow normal breathing, and Pickwickian syndrome, also known as obesity hyperventilation syndrome or obesity sleep apnea. With Pickwickian syndrome, so named for a character called Joe the Fat Boy in the Charles Dickens novel Pickwick Papers, the person may fall asleep at inappropriate times, retain high levels of carbon dioxide in the lungs since the lungs do not expel this substance properly, appear bluish in color, develop heart failure due to enlargement of the heart, and experience sleep apnea, where they stop breathing hundreds of times during sleep. This condition may be life threatening in many cases.
With all of these health problems known to be associated with obesity, experts have made it a priority to educate the public about the risks. Still, the incidence of obesity continues to rise, resulting in more medical problems and expenses each year despite warnings about the consequences of being obese.