Background Conventional anthropometric indices (body mass index (BMI) and waist circumference (WC)) have limitations, in part, due to ethnic differences in fat distribution. Assessment of abdominal body composition using magnetic resonance imaging (MRI) is increasingly used to gain deeper insights into the pathophysiology of diabetes mellitus, cardiovascular diseases and metabolic syndrome, but the knowledge of abdominal volumes in indigenous populations is scarce. This study aimed to assess abdominal fat distribution and total abdominal volume using MRI in a multi-ethnic cohort that includes Maori (the indigenous people of New Zealand) and Pacific Islanders (PI). Methods MRI was used to quantify subcutaneous adipose tissue (SAT) volume, visceral adipose tissue (VAT) volume and total abdominal (TAb) volume by two independent raters in a blinded fashion. WC and BMI were also measured. Multinomial regression was used to compare the volumes between ethnic groups. Linear regression was used to investigate the ethnicity-specific associations between anthropometric indices and abdominal volumes. Three statistical models were built to adjust for age, sex, prediabetes/diabetes status and other covariates. Results A total of 87 individuals (37 Caucasians, 24 Maori/PI and 26 others) were studied. Maori/PI had a significantly higher VAT volume compared with Caucasians across all statistical models, with the highest odds ratio of 2.1 (95% confidence interval: 1.1 - 4.2; P = 0.026). SAT and TAb volumes did not differ significantly between the groups. WC explained up to 72.9% of variance in VAT volume among Maori/PI and up to 50.7% among Caucasians. BMI explained up to 67.6% of variance in VAT volume among Maori/PI and up to 52.1% among Caucasians. Conclusions Greater visceral fat deposition among Maori/PI might go some way towards explaining the increased rates of metabolic disorders observed in this ethnic group. Conventional anthropometric indices do not correspond to the same abdominal volumes across different ethnic groups.

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