This cross-sectional study aimed to determine ethnic and environmental influences on the relationship between BMI and percentage body fat, using a sample of 144 Japanese and 140 Australian-Caucasian men living in Australia, and eighty-eight Japanese men living in Japan. Body composition was assessed by anthropometry using standard international methods (International Society for the Advancement of Kinanthropometry protocol). Body density was predicted using Durnin and Womersley's (1974) equation, and percentage body fat was calculated from Siri's (1961) equation. Significant (P,0·05) ethnic differences in stature, body mass and BMI were observed between Japanese and Australian men, but no ethnic differences were observed in their percentage body fat and height-corrected sum of skinfold thicknesses. No differences were found in the BMI -percentage body fat relationship between the Japanese subjects living in Australia and in Japan. Significant (P,0·05) ethnic differences in the BMI-percentage body fat relationship observed from a comparison between pooled Japanese men (aged 18-40 years, BMI range 16·6 -32·8 kg/m 2 ) and Australians (aged 18 -39 years, BMI range 16·1 -31·4 kg/m 2 ) suggest that Japanese men are likely to have a greater percentage body fat than Australian men at any given BMI value. From the analyses, the Japanese men were estimated to have an equivalent amount of body fat to the Australian men at BMI values that were about 1·5 units lower than those of the Australians (23·5 kg/m 2 and 28·2 kg/m 2 , respectively). It was concluded that Japanese men have greater body fat deposition than Australian-Caucasians at the same BMI value. Japanese men may therefore require lower BMI cut-off points to identify obese individuals compared with Australian-Caucasian men.

The purpose of this study was to investigate if obese children have reduced knee extensor (KE) strength and to explore the relationship between adiposity and KE strength. An observational case-control study was conducted in three Australian states, recruiting obese [N = 107 (51 female, 56 male)] and healthy-weight [N = 132 (56 female, 76 male)] 10- to 13-year-old children. Body mass index, body composition (dual energy X-ray absorptiometry), isokinetic/isometric peak KE torques (dynamometry) and physical activity (accelerometry) were assessed. Results revealed that compared with their healthy-weight peers, obese children had higher absolute KE torques (P ≤ 0.005), equivocal KE torques when allometrically normalized for fat-free mass (FFM) (P ≥ 0.448) but lower relative KE torques when allometrically normalized for body mass (P ≤ 0.008). Adjustments for maternal education, income and accelerometry had little impact on group differences, except for isometric KE torques relative to body mass which were no longer significantly lower in obese children (P ≥ 0.013, not significant after controlling for multiple comparisons). Percent body fat was inversely related to KE torques relative to body mass (r = -0.22 to -0.35, P ≤ 0.002), irrespective of maternal education, income or accelerometry. In conclusion, while obese children have higher absolute KE strength and FFM, they have less functional KE strength (relative to mass) available for weight-bearing activities than healthy-weight children. The finding that FFM-normalized KE torques did not differ suggests that the intrinsic contractile properties of the KE muscles are unaffected by obesity. Future research is needed to see if deficits in KE strength relative to mass translate into functional limitations in weight-bearing activities.

Rowers competing at the 2000 Olympic Games were measured for 38 anthropometric dimensions. The aim was to identify common physical characteristics that could provide a competitive advantage. The participants included 140 male open-class rowers, 69 female open-class rowers, 50 male lightweight rowers, and 14 female lightweight rowers. Body mass, stature, and sitting height were different (P < 0.01) between the open-class and lightweight rowers, as well as a comparison group of healthy young adults ("non-rowers", 42 males, 71 females), for both sexes. After scaling for stature, the open-class rowers remained proportionally heavier than the non-rowers, with greater proportional chest, waist, and thigh dimensions (P < 0.01). Rowers across all categories possessed a proportionally smaller hip girth than the non-rowers (P < 0.01), which suggested the equipment places some constraints on this dimension. Top-ranked male open-class rowers were significantly taller and heavier and had a greater sitting height (P < 0.01) than their lower-ranked counterparts. They were also more muscular in the upper body, as indicated by a larger relaxed arm girth and forearm girth (P < 0.01). For the male lightweight rowers, only proportional thigh length was greater in the best competitors (P < 0.01). In the female open-class rowers, skinfold thicknesses were lower in the more highly placed competitors (P < 0.01). In conclusion, the rowers in this sample demonstrated distinctive physical characteristics that distinguish them from non-rowers and other sports performers.

Overweight and obesity in Asian children are increasing at an alarming rate; therefore a better understanding of the relationship between BMI and percentage body fat (%BF) in this population is important. A total of 1039 children aged 8 -10 years, encompassing a wide BMI range, were recruited from China, Lebanon, Malaysia, The Philippines and Thailand. Body composition was determined using the 2 H dilution technique to quantify total body water and subsequently fat mass, fat-free mass and %BF. Ethnic differences in the BMI -%BF relationship were found; for example, %BF in Filipino boys was approximately 2 % lower than in their Thai and Malay counterparts. In contrast, Thai girls had approximately 2·0 % higher %BF values than in their Chinese, Lebanese, Filipino and Malay counterparts at a given BMI. However, the ethnic difference in the BMI-%BF relationship varied by BMI. Compared with Caucasian children of the same age, Asian children had 3 -6 units lower BMI at a given %BF. Approximately one-third of the obese Asian children (%BF above 25 % for boys and above 30 % for girls) in the study were not identified using the WHO classification and more than half using the International Obesity Task Force classification. Use of the Chinese classification increased the sensitivity. Results confirmed the necessity to consider ethnic differences in body composition when developing BMI cut-points and other obesity criteria in Asian children.

As anticipated, obesity appears to undermine physical functioning in children, including the capacity to perform basic locomotor skills yet, unexpectedly, participation in key life areas related to physical functioning appeared largely unaffected.

The objective of the present study was to determine differences in predicting total and regional adiposity using the waist:height ratio (WHtR) calculated using different 'waist' measurements. Body composition of ninety-five males and 121 female Australian adults (aged 20 years and above) was measured using dual-energy X-ray absorptiometry. The WHtR was calculated using: (1) the narrowest point between the lower costal border and the top of the iliac crest (WHtR-W), and (2) at the level of the umbilicus (WHtR-A). Relationships between calculated WHtR and measured body composition, such as percentage body fat (%BF) and percentage trunk fat (%TF) were determined. Values obtained from WHtR-A were significantly greater than WHtR-W in both groups (P, 0·05). While no correlation differences between WHtR-W and WHtR-A in relation to body composition variables were observed, females showed significantly lower correlation with lean mass compared with BMI. Regression analyses showed that neither WHtR had an age influence on %TF estimation. Estimated %BF and %TF were comparable for both WHtR and also with estimated values using a BMI of 25 kg/m 2

Body composition is commonly predicted from bioelectrical impedance spectroscopy using mixture theory algorithms. Mixture theory algorithms require the input of values for the resistivities of intra-and extracellular water of body tissues. Various derivations of these algorithms have been published, individually requiring resistivity values specific for each algorithm. This study determined apparent resistivity values in 85 healthy males and 66 healthy females for each of the four published mixture theory algorithms. The resistivity coefficients determined here are compared to published values and the inter-individual (biological) variation discussed with particular reference to consequential error in prediction of body fluid volumes. In addition, the relationships between the four algorithmic approaches are derived and methods for the inter-conversion of coefficients between algorithms presented.

The body composition of 139 Japanese females and 84 Japanese males (aged 18-30 years) was measured using anthropometry to assess gender differences in body perceptions in relation to their measured values. Participants were asked to rate perceptions of their own "heaviness" and "fatness" and these were compared to their BMI and percent body fat (%BF). Japanese females showed a significantly greater desire to lose body weight (-4.20+/-0.6 kg) compared to males (0.27+/-1.4 kg). Females also showed poor understanding of their "heaviness" and "fatness" in relation to actual body composition compared to males. The results confirmed distinct gender differences in body perception in relation to actual body composition and attitudes to weight management. Further promotion of "healthy" body image is recommended for the Japanese population.