Low body mass index but high percent body fat in Taiwanese subjects: Implications of obesity cutoffs

OBJECTIVES: To compare the different correlations of body mass index (BMI) and percent body fat (BF%) with other ethnic groups and to evaluate the appropriateness of Asia-Pacific redefining obesity criteria in the Taiwanese population. The corresponding BF% to BMI cutoffs of overweight and obesity will also be studied. DESIGN: A cross-sectional epidemiological survey. SUBJECTS: A total of 509 male and 570 female Taiwanese subjects aged ≥20y sampled by the systematic stratified clustering sampling method were analyzed. MEASUREMENTS: BMI was obtained by body weight (kg) divided by squared body height (m²). The estimated BMI (BMIe) was deduced from the Caucasian-based four-compartment equation (4C). BF% measured by the methods of dual-energy X-ray absorptiometry (DXA) or Caucasian-based 4C were used and abbreviated as DXA-BF and 4C-BF, respectively. RESULTS: The curvilinear relationship between age and BMI or DXA-BF was established. When compared by age-stratified groups, Taiwanese subjects had a higher BF% (4C-BF) in any given BMI than Caucasians. That is, the level of 4C-BF for BMI≥25 kg/m² in Taiwanese subjects was similar to BMI≥30 kg/m² in Caucasians. The BMIe values of 25 and 30 kg/m² were nearly equal to the BMIs of 23.6 and 25.3 kg/m² in males, and 22.7 and 24.8 kg/m² in females, respectively. The 4C-BF of 25% was nearly equal to a BMI of 26.2 kg/m² in males, and 35% was equal to a BMI of 24.4 kg/m² in females. Consequently, the DXA-BF cutoffs for BMIs of 23 and 25 kg/m² were compatible to 23 and 25% in males, and 35 and 38% in females, respectively. CONCLUSION: It was demonstrated that Taiwanese subjects had a relatively lower BMI but a higher BF% than Caucasians. In general, the newly proposed Asia-Pacific BMI cutoffs for overweight (≥23 kg/m²) and obesity (≥25 kg/m²) may be acceptable to both male and female Taiwanese subjects. The corresponding BF% (DXA-BF) cutoffs for obesity would be 25% in male and 38% in female Taiwanese subjects, respectively.