Relationship between body mass index and percentage of body fat, estimated by bio-electrical impedance among adult females in a rural community of North India: A cross-sectional study.

Introduction: Body adiposity measured by percentage of body fat (BF%) is found to be better predictor of cardiovascular morbidity and mortality than body mass index (BMI). Limited information exists showing relationship between BMI and BF% in North Indian population.

Objectives: To study the relationship between BMI and BF% among North Indian adult females across various age strata and level of BMI.

Materials and Methods: This was a cross-sectional study conducted at Ballabgarh Health and Demographic Surveillance Site (HDSS) among randomly selected females. BMI using standard techniques and BF% using bioelectrical impedance analysis was estimated. Linear regression was performed using general linear model with BF% as dependent variable and BMI as main independent variable.

Results: Mean (±2 SD) age of participants was 41.3 ± 15.7 years. Mean BMI (±SD) was 23.3 (±4.6) kg/m2, whereas mean fat mass (±2 SD) and BF% (±95% CI) was 19.2 (±7.9) kg and 33.6 (±6.9) %. BMI and BF% were highly correlated among obese (r = 0.77), whereas least correlated (r = 0.32) in underweight females. Across age strata, correlation between BMI and BF% was maximum in 18-35 years age group (r = 0.95), whereas least in females ≥56 years (r = 0.67). Age and BMI together predicted 73% of variability in BF% in hierarchical linear regression model.

Conclusions: In this population, we have found strong correlation between BMI and BF% particularly at higher level of BMI and in younger females. There is need to conduct more robust prospective longitudinal studies to assess BF%, which is a better predictor of cardiovascular morbidity and mortality.