Ethnic differences in the association between body mass index and impedance index (Ht<sup>2</sup>/Z) in adult women and men using a leg-to-leg bioimpedance method
Siervo M., Davies AA., Jebb SA., Jalil F., Moore SE., Prentice AM.
Background: Ethnic differences in the association between body mass index (BMI) and body fat suggest that body composition varies across ethnic groups. Objective: To investigate the association between impedance index - a measure of tissue resistivity - and BMI in adults of different ethnic groups (Asian Indians, West Africans and White Caucasians) living in their native countries. Methods: Male (n = 329) and female (n = 277) adult subjects (18-50 years) living in urban areas in the UK, The Gambia and Pakistan were studied. Body weight and height were measured and BMI calculated. The same leg-to-leg bioimpedance instrument was used in each study and impedance index (height2(cm)/impedance (ω)) used as measure of tissue resistivity. Results: In women, Asian Indians and West Africans had a significantly greater increase in impedance index per unit increase in BMI compared with white Caucasians (P < 0.001). In men, Asian Indians had a significantly lower impedance index compared with West Africans and white Caucasians (P < 0.001). Conclusion: Different ethnic groups may have different tissue resistivity for the same BMI indicative of systematic differences in body composition.