Body mass index, or BMI, has become the standard initial indicator of body fatness.Health practitioners use it as a screening tool for obesity. Frame size refers to the size and breadth of your bones and other supportive tissues. It's not as widely used as BMI, but the two tell healthcare providers about your risk for certain diseases. Neither are perfect tools, but they are more convenient and simpler to use in a typical doctor's office setting.
Body Mass Index
The body mass index is a formula designed to give your healthcare provider a proxy for your level of body fatness. It measures your weight in relation to your height. The formula is your weight in kilograms divided by the square of your height in meters or your weight in pounds divided by your height in inches squared and multiplied by 703. If the resulting two-digit number is 25 or greater, you are considered overweight. If it's higher than 30, you are considered obese. The BMI formula was developed in 1832 by a Belgian astronomer and it wasn't initially meant to determine obesity risk; it was a formula Adolphe Quetelet designed as part of his overall quest to find the average dimensions of men.
BMI Not a Perfect Tool
Public health authorities acknowledge that the BMI isn't a perfect tool and it doesn't directly measure body fat. Critics say the adult calculation doesn't distinguish between a muscle-bound male Olympian and a 75-year-old grandmother, for example. However, BMI is widely accepted as a convenient screening tool for obesity, heat diseases and other health problems. The BMI tells your healthcare provider whether additional examinations are needed.
Frame Size
For several decades, the nebulous "frame size" was used in determining ideal weight. Frame size describes your skeletal size along with your body's support structure. Colloquially, you might hear someone's frame size in terms like "big boned." The idea was that your bone and internal support structure doesn't fluctuate like body fat, so frame size was once considered a good metric for figuring out what you should weigh. Frame size has had a number of measurements. It's commonly estimated by measuring the width of bones, such as the shoulders, hips, wrists, elbows, knees and ankles and comparing them to national reference data. However, MedlinePlus describes frame size as being determined by the circumference of your width in relation to your height. The service gives the example of a man who is 5-ft, 5-in with a wrist measuring 6 in is considered "small boned."
Frame Size Relationship with BMI
Although frame size isn't used as ubiquitously as BMI, they are related. A group of medical researchers from Wright State University School of Medicine studied frame size in more than 500 men and women and reported their findings in the June 2002 "American Journal of Clinical Nutrition." They reported that frame size was significantly and positively correlated with levels of body fatness along with fat-free mass. Like MedlinePlus, they found that wrist measurements were the best indicator of the association between frame size and the amounts of fat and muscle. In addition, they said accounting for frame size in relation to body composition, like the BMI, has been to help identify people with a health risk.
References
- CDC; Body Mass Index; February 2011
- HealthStatus: Frame Size
- "American Journal of Clinical Nutrition"; Relations between Frame Size and Body Composition and Bone Mineral Status; William Cameron Chumlea et al.; June 2002
- Slate; Beyond BMI: Why Doctors Won't Stop Using an Outdated Measure for Obesity; Jeremy Singer-Vine; July 20, 2009
Member Comments