BMI or Body Composition Score. What do they mean?
When it comes to a recommended weight and your overall health, clinicians talk about BMI and body composition. Let’s break it down.
Body Mass Index (BMI)
The Body Mass Index score is a single number that represents a measure of your body fat based on your height and weight. You find your BMI score by following the formula (divide weight in pounds by height in inches squared, then multiply by conversion factor of 703) or by using one of many online BMI calculators available online. The CDC provides the following guidelines for BMI for adults:
- Underweight – less than 18.5
- Healthy weight – 18.6 – 24.9
- Overweight – 25 – 29.9
- Obese – 30 – 39.9
- Morbidly Obese – 40 or greater
For children, BMI guidelines need to take into account the child’s age and sex, and are interpreted in terms of percentiles. See the CDC growth charts here.
In general, as your BMI increases, so does your risk for weight-related diseases, such as diabetes and cardiovascular disease. However, studies in recent years point to body fat percentage as a better indicator of health/disease risk. BMI, while useful, does not account for muscle mass versus body fat in the calculation.
Body Composition Score
Your body composition score can be found by using a number of different devices, including calipers or a body composition scale. Your body composition is the proportion of body fat to non-fat mass (or lean tissue). Our office uses a Body Composition Scale that sends a small electric current when you step on the scale’s sensors. The current measures the level of ‘resistance’ providing you with your weight and an estimated percentage of your overall body fat. Two people might have the same BMI score, but one might be overweight, while the other is fit. By using a Body Composition Score, you and your doctor have a better idea of your total percentage of body fat, and we know that higher percentages of body fat increase your risk for certain diseases.
While both of these scores are valuable, your doctor considers these scores in context with other factors, including sex, waist measurement, etc. For example, women tend to have higher body fat percentages than men, and older adults and people of Asian descent tend to have higher scores. Your doctor also will discuss WHERE your body is storing fat—studies show us that fat in the abdominal area is more dangerous than fat in other areas of the body.
Tracking your body composition is a good way to see your progress if you are on an exercise and/or weight loss program. Often times, the (body weight) scale doesn’t move, but a person can still be shedding fat while gaining muscle mass. Knowing your body composition is just one more factor for you and your doctor to consider when creating your personalized wellness plan.