What is BMI?
By Jessica Bosari
BMI is a formula used to determine a person’s Body Mass Index. The BMI number is seen by the medical establishment as a reliable indicator to estimate a person’s body-fat percentage and risk of obesity-related health problems. The formula is calculated by diving weight by height squared, and then multiplying by 703. Weight calculation is in pounds and height in inches.
How to Calculate Your Body Mass Index
For instance, if you weigh 150 pounds, and you are 5’8” tall, you would work out your BMI by first squaring your height. 5’8” is the same as 68 inches. 68 inches squared is 4,624. Divide 150 pounds by 4,624 inches and you get .0324. Multiply this number by 703 and your BMI calculation is 22.8. If you prefer, you can multiply your weight by 703, then divide by height and then divide by height again. The result is the same.
What Your BMI Means
BMI calculations will fit into one of four categories. Those who are underweight have a BMI of less than 18.5. A BMI between 18.5 and 24.9 is normal. If your BMI is between 25.0 and 29.9, you are considered overweight. Finally, a BMI over 3.0 indicates obesity.
Doctor’s will also consider waist size when evaluating BMI. This is because someone with high muscle mass may have the same BMI as someone less healthy, but the person with greater muscle mass will have a smaller waist size. Men with a waist size of over 40 inches and women over 35 inches tend to suffer from obesity-related illness.
Usefulness of BMI
BMI is an important tool for helping assess the health risks of patients because it is easy to calculate in an office setting. Obesity can lead to many problems, most of which can be fatal. By assessing a patient’s BMI, the doctor has a basic tool that helps determine if further testing is needed.
Obesity Health Risks
Heart disease is the most commonly obesity-related disease. The excess body fat raises blood cholesterol and blood pressure, both common risk factors for heart disease. Those who were obese as children are much more likely to die from heart disease as adults.
Type 2 diabetes is another strong risk factor. The foods that cause people to become obese are often high in fat. Such a diet triggers the liver to produce abnormal levels of glucose. High levels of blood glucose lead to insulin resistance. When this happens, body tissues cannot accept glucose as easily as a healthy person can. In order to deliver glucose to body tissues, more insulin is needed so the glucose does not remain in the bloodstream, creating health problems.
Obesity can also create degenerative problems with joints like knees and hips. It is not just the extra weight putting pressure on these joints. Researchers believe that metabolic and mechanical factors associated with obesity may also increase the risk of osteoarthritis in joints like the thumb.
Gallstones are also more common in the obese. The liver in an obese person produces too much cholesterol, which then supersaturates bile in the gallbladder.
Respiratory ailments are also a problem for obese individuals. The excess weight of the chest wall becomes exacerbated by a decrease in lung size. Obese people face the challenge of needing more oxygen to carry around the excess weight, yet they have a decreased ability to get that vital oxygen to their tissues.
Obesity and Cancer
The obese also suffer an increased risk of contracting 20 types of cancer. Among the most common are colon, breast, endometrial, kidney, and esophagus cancers. It is believed that the foods that make a person obese are the culprits in cancer as well, since those who eat a well-balanced diet are usually slimmer and show a decreased risk of cancer.
Sleep apnea is a problem for the obese as well. Apnea is a condition where the individual episodically stops breathing for ten seconds or so while asleep. The drop in oxygen can be fatal. The excessive amounts of fat in an obese person’s neck actually restrict the airway, cutting off the supply of oxygen.
All these problems would be costly and difficult to screen using blood and urine tests or CT scans. By utilizing the BMI, doctors are able to assess a patient’s level of risk for these conditions before ordering expensive testing.