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Body size and composition in Polynesians
B A Swinburn1, S J Ley, H E Carmichael
1Department of Community Health, University of Auckland, Auckland, New Zealand. b.swinburn@auckland.ac.nz
Objectives:
To compare the relationship between body size and body composition in New Zealanders of Polynesian and European descent and to develop specific regression equations for fat mass for Polynesians.
Subjects:
189 Maori (93 males, 96 females), 185 Samoans (88 males, 97 females) and 241 Europeans (89 males, 152 females) aged 20-70 y.
Measurements:
Height, weight, four skinfold thicknesses, bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DXA).
Results:
At higher body mass index levels, Polynesians (Maori and Samoans combined) had a significantly higher ratio of lean mass:fat mass compared with Europeans. Four multiple regression equations incorporating resistance and reactance, height and weight, sum of four skinfolds or sum of two skinfolds were developed in two-thirds of the Polynesian participants using DXA fat mass as the dependent variable. In the remaining one-third of participants, the mean difference between fat mass predicted by these equations (r2 range 0.89-0.93) and DXA fat mass ranged from -0. 06 to +0.25 kg (s.d. -3.67 to +3.71 kg).
Conclusion:
At higher BMI levels, Polynesians were significantly leaner than Europeans, implying the need for separate BMI definitions of overweight and obesity for Polynesians. The regression equations using BIA, height and weight or skinfold thicknesses were good predictors of body composition in Polynesians.