Clearly, each individual can weigh too much or too little to be healthy. The underweight person has minimal body fat stores and is at a disadvantage in situations where energy reserves are needed, such as a prolonged period of physiological stress or injury. Other problems for the underweight person may include menstrual irregularity, infertility, and osteoporosis.
The physical risks of overweight and obesity are greater for some people than for others, depending on inherited susceptibilities to conditions such as high blood pressure, high blood cholesterol, and diabetes. High blood pressure is made worse by weight gain and can often be normalized merely by weight loss. Diabetes can be precipitated, in genetically susceptible people, by becoming overweight.
Obesity also increases the risk of heart disease, partly because excess fat pads crowd the heart muscle and the lungs within the body cavity. These fat pads encumber the heart as it beats, requiring it to work harder to deliver oxygen and nutrients to the rest of the body. Also, the lungs cannot expand fully, thus limiting the oxygen intake of each breath and causing the heart to work even harder. Furthermore, because each extra pound of fat tissue demands to be fed by way of miles of capillaries, the heart must work extra hard in obese people to pump blood through a network of blood vessels that is vastly larger than that of a thin person. Even a healthy heart is strained by excess fat. When a diseased heart finds itself in this bind, a sudden increase in workload may be more than it can handle.
Gallbladder disease, too, can be brought on in susceptible people merely by excess weight.7 Similarly, obesity increases a woman’s risk of developing breast cancer.8 Table 9-1 shows additional conditions that can be caused, or made worse, by obesity.
In addition to being at risk for these health hazards, millions of obese people incur risks from ill-advised, misguided diet programs. Some fad diets are actually more hazardous to health than obesity! Many claims, treatments, devices, and gadgets for losing weight are, at best, simply ineffective, whereas others are truly dangerous. Over the centuries, “magic” weight-loss plans have been offered time and again, and their success lies in their popularity, not in their results.
Although some obese people suffer none of these physical health hazards, no one in our society quite escapes one disadvantage of obesity. In many parts of North America, obesity is a social and economic handicap.9 Obese individuals suffer from discrimination in many areas, including social relationships and the job market. Psychologically, a body size that embarrasses or shames a person can be a private anguish. For people who perceive themselves as fat in a society that prizes thinness, real or imagined obesity can thrust them into withdrawal, shame, humiliation, and isolation.