Do You Know Your BMI?

Obesity is a national epidemic. According to the 1999-2000 National Health and Nutrition Survey, almost two-thirds of American adults are overweight and 30.5% are obese. Obesity differs from being overweight. Overweight usually refers to excess body weight compared to a set standard. Obesity refers to excess body weight from a high proportion of body fat.

The most widely accepted method to determine if an individual is overweight or obese is called the Body Mass Index (BMI). To calculate your BMI, multiply your weight in pounds by 704.5, then divide the result by your height in inches, and divide that result by your height in inches a second time. If you have access to the Internet, you can use the BMI calculator at http://www.nhlbi.nih.gov/guidelines/obesity/BMI/bmicalc.htm.

A widely accepted definition of overweight is a BMI between 25 and 29, and obese as a BMI of 30 or more. As with any generalized measurement, there are certain drawbacks to the BMI model. It isn’t gender or age specific. Also, certain very muscular individuals may be categorized as overweight when they actually have extra muscle mass, not fat. Most research on nutrition, however, does use the BMI.

According to government studies, obesity and overweight are risk factors for diabetes, heart disease, stroke, high blood pressure, gallbladder disease, osteoarthritis (wear and tear arthritis), sleep apnea and some forms of cancer. Obesity is also associated with high blood cholesterol, complications of pregnancy, menstrual irregularities, stress incontinence, depression, and increased surgical risk.

From a biomechanical perspective, obesity changes your posture so that your body can more easily carry the excess weight. As your weight increases, you naturally widen your base support by standing with your feet farther apart. Since joints such as the hips, knees and feet aren’t designed to bear weight in this position, changes start to occur.

In many cases, the angle between the thighbone (femur) and the shin bone (tibia) begins to change. In some cases, a person becomes “knocked kneed,” also called genu valgus. This usually accompanies pronated (flat) feet as the angle at the ankle changes. In other cases, the knees become bowed, causing more pressure on the outside of the feet. All of these biomechanical changes to the weight bearing joints increase the wear on the joints and contribute to arthritis.

In addition to changes in the hips and legs, the low back undergoes tremendous stress. Often, muscles start to spasm just to hold a person upright. As head, neck and shoulders drift forward, additional strain is put on the neck and the spine compresses.

A scenario heard often by physical therapists involves weight gain after an injury. Common are comments like “I’ve gained 30 pounds since I hurt my back” or “I need to exercise to keep my weight down, and I can’t exercise because of pain.” This Catch-22 situation often requires a multi-faceted approach.

Find a therapist who evaluates the cause of the orthopedic problem in a holistic biomechanical approach. Once both the cause and symptoms are addressed, a safe and successful exercise program can be followed. Aquatic or pool exercise is often ideal because there is much less stress placed on weight-bearing joints. Nutritional counseling should also be sought to develop appropriate eating habits. Last but not least –always check with a physician to initiate any exercise program.

Awareness is the key. Recognize that there is a problem and take steps to improve your physical fitness level.