What Are The Health Risks of Obesity?

What are the health risks of being overweight?Obesity is an excess accumulation of body fat. Although the underlying mechanisms that regulate body fat metabolism are still being sorted out, obesity is clearly the result of an imbalance between energy intake and expenditure.

Obesity has long been considered to be a behavioral disease explained by inappropriate eating and activity habits. Recent scientific studies have indicated, however, that obesity is the result of many complex interactions between behavioral, cultural, psychological and biological factors. It is important to keep in mind that obesity has multiple causes.

Although there is still debate on many aspects of the causes of obesity, it is clear that the balance of energy expenditure, through exercise, and energy intake, through diet, are central to the development or prevention of obesity. The precise determination of the amount of body fat in a person requires technically sophisticated methods that are not generally available to the public. Rough estimates of the amount of body fat, or adipose tissue, can be easily obtained through the use of various anthropometric methods. One of the simplest and most common methods is the calculation of body mass index (BMI). BMI has been shown to correlate well with sophisticated measurements of body fatness and with the risk for adverse health effects.

Increased body weight represents a significant risk for development of non-insulin dependent diabetes mellitus (NIDDM), hypertension (high blood pressure), hypercholesterolemia (high blood cholesterol), coronary artery disease (CAD) and several forms of cancer. For individuals 20 percent above their desirable body weight, the prevalence of hypertension (blood pressure greater than 160/95) is nearly 3 times higher than among non-overweight individuals. Being overweight more than doubles the incidence of hypercholesterolemia (blood cholesterol above 200 mg/dl) compared to normal weight individuals. The incidence of diabetes is almost tripled in overweight men and women compared to their non-overweight counterparts. Obesity is also associated with a higher mortality from many forms of cancer in both men and women. In men, risk of cancer of the colon, rectum and prostate is increased by obesity, while in women, elevated body fatness increases the risk of cancer of the breast, gallbladder and bile ducts, uterus and ovaries.

Data from a number of large insurance studies have indicated that the higher the degree of obesity, the higher the rate of premature death. Even moderate degrees of overweight substantially increase the risk for chronic disease. Because of the substantial difficulties encountered in trying to lose large amounts of weight, it may be more realistic for many people to focus their efforts not so much on weight loss, but on increasing physical activity. With regular physical activity, modest reductions in body weight and body fat (10% or less) are easy to achieve and maintain, yet they can result in dramatic improvements in health.

Of the diseases listed above NIDDM, hypertension, hypercholesterolemia, CAD and cancer all respond well to modest weight reductions. The insulin insensitivity, hyperinsulinemia and impaired glucose tolerance of NIDDM are improved by weight loss. A weight reduction of as little as 5% of initial body weight has been shown to improve glycemic control and substantially prolong survival time of patients diagnosed with NIDDM. Hypertension responds remarkably well to modest weight loss, primarily due to reductions in cardiac output, blood volume, intracellular sodium and insulin resistance that are characteristic of obesity.

Although CAD has many causes, weight loss improves several important CAD risk factors. Blood levels of triglycerides, total cholesterol, low density lipoproteins (LDL) and insulin are reduced by weight loss, while high density lipoprotein (HDL) levels are increased-especially when weight loss is achieved through a combination of diet and exercise. The methods used to bring about a loss of body weight, the rate of weight loss and the length of time that weight loss is maintained will influence the degree to which weight loss provides beneficial health effects.

It is clear that the more overweight a person is the more likely they are to benefit from weight loss. Because of the difficulties encountered with achieving and maintaining large body weight losses, it may be more desirable to encourage a modest degree of weight loss that is more easily maintained over a longer period of time.

by Shawn Talbott, Ph.D.