BMI — Not the Final Word on Healthy Weight

May 23, 2017

BMI has its limitations because it calculates body mass index based merely on height and weight. It does not take into consideration age, gender, frame size, or muscle mass.

For instance, adult BMI calculators should not be used for children under 19 years of age because the percentage of body fat changes throughout childhood and adolescence. Men often have larger body frames than women, so their BMI might skew higher. An athlete’s BMI could be misleadingly high due to increased muscle mass, and an infirm or elderly person’s BMI could be deceptively low due to muscle atrophy.

BMI is a starting point, but it really doesn’t tell you the ratio of muscle mass versus fat. And body fat is what puts you at a greater risk for disease, especially when your waist circumference is high. The National Heart, Lung, and Blood Institute (NHLBI) states, “If most of your fat is around your waist rather than at your hips, you’re at a higher risk for heart disease and type 2 diabetes.”

Regardless of BMI or a seemingly normal weight, a waist circumference of greater than 40 inches for men and 35 inches for women is considered a risk factor that requires taking a closer look at your entire health and wellness picture.

• What is your daily activity level and diet?
• What are your blood pressure, cholesterol, and blood glucose levels?
• What is your family history of cardiovascular disease, diabetes, and hypertension?

View the NHLBI’s BMI/waist circumference/risk chart. If you find you are bordering on a higher risk for weight-related disease, even a five to 10 percent weight loss can reduce that risk substantially.

BMI is a valuable tool for risk assessment, but your physician is the best resource to interpret BMI within the context of your physical makeup, waist circumference, and overall health. Please call on him or her if you have any concerns.

Author of this article

Holly Smith, MD, specializes in family medicine. She is a guest columnist and located at IU Health Physicians Primary Care – Anson, 6866 W. Stonegate Drive, Suite 100, in Zionsville. She can be reached by calling the office at 317.768.6000.

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