Skip to main content
ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #61973
Title: PREDICTING BODY FATNESS: THE BODY MASS INDEX VS ESTIMATION BY BIOELECTRIC IMPEDANCE

Author
item ROUBENOFF, RONENN - TUFTS-HNRCA
item DALLAL, GERARD - TUFTS-HNRCA
item WILSON, PETER - FRAMINGHAM HEART STUDY

Submitted to: American Journal of Public Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/1994
Publication Date: N/A
Citation: N/A

Interpretive Summary: Researchers and health professionals often use body mass index (weight in kilograms/height in square meters) to determine the percentage of fatness in an individual. With the advent of bioelectrical impedance analysis (BIA), more precise measurement of fatness in populations is now possible. BIA is a process that measures the length of time it takes for a an electric shock to pass from one point of the body to another. The speed of the shock is determined by the amount of fat mass in the body. Since fat is a poor conductor, the electric shock moves slower through individuals with greater fat mass. We measured height, weight, and then percentage of fat by BIA in 2032 adults, ages 31 to 92, participating in the Framingham studies. Our results indicate the body mass index was a poor predictor of fatness in both women and men, and was imprecise (standard error of estimate = 5 percentage points). Age in women and, to a lesser extent, in men had a significant effect on accuracy as well. These data suggest that body mass index is an imprecise measurement of fatness compared with bioelectrical impedance.

Technical Abstract: The body mass index (weight in kilograms/height in square meters) is a common surrogate for fatness. With the advent of bioelectrical impedance analysis, more precise measurement of fatness in populations is now possible. We measured height, weight, and percentage of fat by bioelectrical impedance analysis in 2032 adults, ages 31 to 92, who were participating in the Framingham studies. Body mass index was a poor predictor of fatness in both women (R2=0.55) and men (R2=0.38), and was imprecise (standard error of estimate = 5 percentage points). The relationship between percentage fat and body mass index was quadratic in both sexes, and was altered by age in women (P< .0001) and, to a lesser extent, in men (P<.027). These data suggest that body mass index is an imprecise measurement of fatness compared with bioelectrical impedance.