Most people’s primary motivation for weight management is to improve their appearance. Equally important, however, are the many other benefits of proper nutrition and regular exercise.

Weight management through reduction of excess body fat plays a vital role in maintaining good health and fighting disease. In fact, medical evidence shows that obesity poses a major threat to health and longevity. (The most common definition of obesity is more than 25 percent body fat for men and more than 32 percent for women.) An estimated one in three Americans has some excess body fat; an estimated 20 percent are obese.

Excess body fat is linked to major physical threats like heart disease, cancer, and diabetes. (Three out of four Americans die of either heart disease or cancer each year; according to the National Health and Nutrition Examination survey, approximately 80 percent of those deaths are associated with life-style factors, including inactivity.)

For example, if you’re obese, it takes more energy for you to breathe because your heart has to work harder to pump blood to the lungs and to the excess fat throughout the body. This increased work load can cause your heart to become enlarged and can result in high blood pressure and life-threatening erratic heartbeats.

Obese people also tend to have high cholesterol levels, making them more prone to arteriosclerosis, a narrowing of the arteries by deposits of plaque. This becomes life-threatening when blood vessels become so narrow or blocked that vital organs like the brain, heart or kidneys are deprived of blood. Additionally, the narrowing of the blood vessels forces the heart to pump harder, and blood pressure rises. High blood pressure itself poses several health risks, including heart attack, kidney failure, and stroke. About 25 percent of all heart and blood vessel problems are associated with obesity.

Clinical studies have found a relationship between excess body fat and the incidence of cancer. By itself, body fat is thought to be a storage place for carcinogens (cancer-causing chemicals) in both men and women. In women, excess body fat has been linked to a higher rate of breast and uterine cancer; in men, the threat comes from colon and prostate cancer.

There is also a delicate balance between blood sugar, body fat, and the hormone insulin. Excess blood sugar is stored in the liver and other vital organs; when the organs are “full,” the excess blood sugar is converted to fat. As fat cells themselves become full, they tend to take in less blood sugar. In some obese people, the pancreas produces more and more insulin, which the body can’t use, to regulate blood sugar levels, and the whole system becomes overwhelmed. This poor regulation of blood sugar and insulin results in diabetes, a disease with long-term consequences, including heart disease, kidney failure, blindness, amputation, and death. Excess body fat is also linked to gall bladder disease, gastro-intestinal disease, sexual dysfunction, osteoarthritiis, and stroke.