Physical activity cut-offs and risk factors for preventing child obesity in Japan.

BACKGROUND: There is no official recommendations for physical activity level or steps for preventing and improving child obesity in Japan. METHODS: Three hundred and two Japanese children aged 9-12 years were recruited wore 3-D speed sensors. Subjects were divided into two groups using the criteria for child obesity in Japan. Body composition was measured on bioelectrical impedance analysis. Physical fitness test was done to evaluate physical strength. Twenty-four hour total steps, energy expenditure, and metabolic equivalents (MET) from Monday to Sunday were consecutively measured. The cut-offs for steps and physical activity level for preventing child obesity were evaluated on receiver operating characteristic curves. Daily life-related risk factors for child obesity were assessed on logistic regression analysis. RESULTS: In both sexes, body volume; bodyweight, body mass index, fat mass, and percentage body fat in the obese group was significantly higher than in the normal group, but age and height were not different (P < 0.001). Aerobic power, running speed, and explosive strength in the obese group were inferior to those in the normal group (P < 0.001). More than 40 min of 4 MET exercise, defined as moderate-vigorous exercise, and 11,000 steps per day are essential to prevent child obesity. Additionally, >2 h TV viewing per day is a significant risk factor for child obesity (OR, 3.43; 95%CI: 1.27-9.31). CONCLUSION: Cut-offs for physical activity and potential risk factors for child obesity have been identified. Recommendations for changes to daily lifestyle for school-aged Japanese children are given.

Effect of exercise on bone status and body composition in Japanese students.

PURPOSE: We evaluated the effect of exercise on stiffness and fat-free mass (FFM), which consists of bone and muscle, in Japanese students. It is uncertain whether exercise or sports activities will help to accumulate overall peak bone mass in Japanese adolescents. METHODS: A total of 710 Japanese students (age = 15-20 yr) were enrolled. Students who regularly engage in physical exercise were assigned to an exercise group; other students were assigned to a nonexercise group. Body composition, including height, weight, waist circumference, hip circumference, body mass index, and waist-to-hip ratio, were measured and calculated. Lung volume, body volume, and body fat percentage were evaluated by air displacement plethysmography. Fat mass and FFM were derived from body fat percentage and body weight. Bone status, such as speed of sounds, broadband ultrasound attenuation, and stiffness, which is defined as bone density, was assessed by quantitative ultrasound. RESULTS: In both sexes, height, weight, body mass index, circumferences, waist-to-hip ratio, lung volume, and body volume between the exercise and nonexercise groups did not show any significant differences. FFM, speed of sounds, broadband ultrasound attenuation, and stiffness in the exercise group were statistically higher than those in the nonexercise group (P < 0.05). Although stiffness positively correlated with age with the exception of the nonexercise group in females (P < 0.01), stiffness correlated with FFM in the exercise and nonexercise groups in both sexes (P < 0.01). CONCLUSIONS: Ours is the first analysis of a trend in peak bone mass, including the effect of exercise in Japanese students. For Japanese pubertal females who did not have a history of regular exercise, stiffness slowly decreased with age. Exercise habits in early childhood are important in the relationship between stiffness and FFM.

A proposed method for the evaluation of body fat in Japanese adults that predicts obesity.

The present study was designed to develop a simple predictive equation for the percent body fat (%BF) in Japanese adults based on variables collected during health examinations. We hypothesized that a benchmark for defining metabolic syndrome and obesity could be based on %BF, which was measured by underwater weighing (UW) as a gold standard for body composition assessment. Thus, we developed a predictive equation for %BF derived from UW that may contribute to the assessment of obesity status, characterized by an excess accumulation of visceral or subcutaneous fat. The subjects were 810 Japanese participants (283 men, 527 women, ages 18-59 years). Anthropometric variables, including height, weight, 7 circumferences, and 8 skinfold thicknesses, were measured. The developed predictive equation was as follows: %BF = 10.558 × sex (1 for men; 2 for women) + 0.069 × age + 0.667 × body mass index + 0.314 × abdominal circumference - 35.881.The coefficient of determination (r(2)) was 0.69. The predicted %BF derived from this equation was highly correlated with UW-measured values and did not show underestimation or overestimation in either sex. These data suggested that this predictive equation for %BF can be used for all Japanese adults and does not require the use of medical equipment and special measurement techniques. By combining the equation for %BF developed in this study with a %BF cutoff value of metabolic syndrome and obesity (>25.0% in men and >30.0% in women), all Japanese adults can easily and conveniently assess obesity status.

An association analysis between mitochondrial DNA A10398G polymorphism and temperament in Japanese young adults.

The mitochondrial (mt) DNA C5178A and A10398G polymorphisms have been reported to be associated with mental disorders such as bipolar disorder. However, the effects of these polymorphisms on temperament in healthy people are poorly understood. Evaluating healthy subjects can have the advantage of providing new strategies for maintaining psychological health and preventing mental illness. We examined the association between mtDNA polymorphisms and temperament in Japanese students. There was no significant difference in examined temperament when analysed by genotypes, 5178-10398 haplotypes, or sex. The subgroup analysis based on sex indicated that there was an interactive effect of the mtDNA A10398G polymorphism and sex on anxiety and obsession. This finding is preliminary and cannot exclude the possibility of false-positive due to small sample size (144 subjects) and multiple statistical testing. Further studies involving a larger sample size or other ethnic groups are necessary to confirm that mtDNA A10398G polymorphism can be a genetic factor for temperament.

Fat-free mass and excess post-exercise oxygen consumption in the 40 minutes after short-duration exhaustive exercise in young male Japanese athletes.

The relationship between fat-free mass (FFM) and excess post-exercise oxygen consumption (EPOC) has not been well researched because of the relatively small number of subjects studied. This study investigated the effects of FFM on EPOC and EPOC/maximum oxygen consumption. 250 Japanese male athletes between 16 and 21 years old from Nagasaki prefecture had their EPOC measured up to 40 minutes after short-duration exhaustive exercise. The value was named as EPOC40 min. The proportions of EPOC up to 1, 3, 6, 10, and 25 minutes to EPOC40 min were calculated and named as P1, P3, P6, P10, and P25, respectively. Body size and composition, VO2max and resting metabolic rate (RMR) were also measured. Mean EPOC40 min was 9.04 L or 158 ml/kg FFM. EPOC40 min was related to FFM (r=0.55, p<0.001) and VO2max (r=0.37, p<0.001). The ratio of EPOC40 min to VO2max was related to FFM (r=0.28, p<0.001). P1, P3, P6, P10, and P25 were negatively related to EPOC40 min/FFM, EPOC40 min/VO2max, and FFM. Athletes who had larger FFM had larger EPOC40 40 min and EPOC40 40 min/VO2max, and smaller P1, P3, P10, and P25.

Are Japanese criteria for obesity useful for screening at risk Japanese? Consideration from anthropometric indices-percentage body fat relationships.

Both childhood and adult obesity are of serious public health concern in Japan. While Japan has diagnostic criteria for both childhood and adult obesity and metabolic syndrome, the appropriateness of the proposed criteria has been questioned. The present study aimed to determine screening ability of anthropometric indices relative to estimated percentage body fat (% BF) and to propose gender- and maturation-specific cut-off points using 1,393 Japanese (552 males and 841 females; 7.6-66.3 years old). Between 20%-50% of individuals with high fat deposits were misclassified using body mass index (BMI), abdominal circumference (AC), abdominal to height ratio (AHtR), and sum of two skinfolds (Sigma2SF). Using the WHO public action point of 23 kg/m2, AC of 80 cm, AHtR of 0.5 for all groups and Sigma2SF of 25 mm for males and 40 mm for females were estimated to be potentially useful cut-off points. The results may indicate a need for further research for appropriate screening cut-off points for Japanese.

Physique, body composition and maximum oxygen consumption of selected soccer players of Kunimi High School, Nagasaki, Japan.

This study evaluates the physical and physiological ability of selected soccer players of Kunimi High School in Nagasaki Prefecture, Japan. The Kunimi team is famous for its intensive training, and had won the championship of the All Japan High School Soccer Tournament six times by 2003. We measured physique, body composition, and maximal oxygen uptake of 72 members aged between 16 and 18 years old between 1986 and 1994. They consisted of 66 outfield players (12 forward players, 23 midfielders, 31 defenders) and 6 goalkeepers. Body density was measured by the under-water weighing method, and Brozek's equation was applied to calculate percentage body fat (%Fat, %), fat-free mass (FFM, kg), FFM/height (FFM/Ht, kg.m(-1)), and FFM index (FFM/Ht(3), kg.m(-3)). The following results were obtained: 1. The average of 66 outfield players was 172.7 cm of height, 64.6 kg of weight, 54.0 cm of girth of thigh, and 90.0 cm of girth of hip, 9.3% of %Fat, 58.6 kg of FFM, 33.9 kg.m(-1) of FFM/Ht and 113.8 kg.m(-3) of FFM index. The mean vital capacity was 4.25 L and total lung capacity was 5.58 L. The mean maximal ventilation was 138.7 L.min(-1), VO(2)max was 3.95 L.min(-1), and VO(2)max/Wt was 61.4 ml.kg(-1).min(-1). 2. Goalkeepers were taller and heavier than outfielders, and had a smaller mean value of VO(2)max/Wt than outfielders (p<0.01). 3. For 23 out of the 72 players measured twice with an interval of about one year, FFM increased and %Fat reduced significantly, while V(E)max, VO(2)max and VO(2)max/Wt did not change. Kunimi players of the present study had as large a VO(2)max/Wt as local players, and a similar or slightly smaller VO(2)max/Wt than national-level players. They had similar %Fat and a similar VO(2)max/Wt with professional soccer players in England (Davis et al., 1992) while they had much smaller physiques.

Limitation of muscle deoxygenation in the triceps during incremental arm cranking in women.

The present study investigated the difference in oxygen kinetics in the exercising muscle between arm cranking and leg cycling in women. Twenty-seven females completed incremental arm cranking and leg cycling tests on separate days. During each exercise, spatially resolved near-infrared spectroscopy was used to measure changes in the tissue oxygen saturation ( SO(2)), oxygenated (oxy-) hemoglobin and/or myoglobin (Hb/Mb), deoxygenated (deoxy-) Hb/Mb, and total Hb/Mb in the triceps during arm cranking and in the vastus lateralis during leg cycling. During arm cranking, there was a rapid increase in the respiratory exchange ratio and a lower ventilatory threshold compared to leg cycling, which confirmed accelerated anaerobic glycolysis in this mode of exercise. During leg cycling, SO(2) remained decreased near to or until approaching peak oxygen uptake (VO(2peak)). During arm cranking, however, the decrease in oxy-Hb/Mb and increase in deoxy-Hb/Mb stopped at the middle of VO(2peak) (mean 51.4%), consequently resulting in a leveling off in the SO(2 )decrease, although total Hb/Mb continued to increase. These results might suggest that the oxygen demand in the triceps attained the maximum at that intensity, despite an adequate oxygen supply during arm cranking.

Body composition and physical fitness of female volleyball and basketball players of the Japan inter-high school championship teams.

This study evaluated the body composition (underwater weighing) and cardiorespiratory function (VO(2)max and O(2)debt max measured by the treadmill exercise test) in 12 members of the women's volleyball team (mean age 17.4 years) and 11 members of the women's basketball team (mean age 17.6 years) that won the championship in the Japan Inter-high School Meeting. We also examined differences in the physical abilities between the members of the top teams of different events. The following results were obtained. (1) The mean values of the height and body weight were 168.7+/-5.89 cm and 59.7+/-5.73 kg in the volleyball players and 166.5+/-7.87 cm and 58.8+/-6.85 kg in the basketball players. (2) The mean %Fat was 18.4+/-3.29% in the volleyball players and 15.7+/-5.05% in the basketball players, and was similar to the reported values in elite adult players. (3) The mean VO(2)max was 2.78+/-0.32 L x min(-1) (46.5+/-2.90 ml x kg(-1) x min(-1)) in the volleyball players and 3.32+/-0.31 L x min(-1) (56.7+/-4.17 ml x kg(-1) x min(-1)) in the basketball players, and was similar to the reported values in elite adult players. (4) The mean O(2)debt max was 6.18+/-1.15 L (103.2+/-12.40 ml x kg(-1)) in the volleyball players and 7.92+/-1.80 L (134.3+/-23.24 ml x kg(-1)) in the basketball players. These values were 2.6 times and 3.3 times as high as the average values in high school students in general. (5) No significant difference was observed in any measured item of the physique, skinfold thickness, or body composition between the volleyball players and basketball players. (6) The VO(2)max and O(2)debt max were 22% and 28% higher in the basketball players than in the volleyball players. From these results, the female volleyball players and basketball players evaluated in this study had the physical abilities needed to win the championship in the Japan Inter-high School Meets, i.e. a large FFM and excellent aerobic and anaerobic work capacities. Also, basketball appears to require higher aerobic and anaerobic work capacities than volleyball.

Phenotypic linkage between single-nucleotide polymorphisms of beta3-adrenergic receptor gene and NADH dehydrogenase subunit-2 gene, with special reference to eating behavior.

The beta(3)-adrenergic receptor gene (BAR-3) allelic variant (Trp64Arg and Arg64Arg) is correlated with obesity or non-insulin-dependent diabetes mellitus. The mitochondrial NADH dehydrogenase subunit-2 gene (ND2) variant (Mt5178A) is associated with longevity or less susceptibility to adult-onset diseases. The frequencies of both the variants are high among the Japanese population. Cross-sectional analysis of these variants was conducted to determine if they correlated well with life-style-related phenotypes and nutrient intake. The body fat rate in the BAR-3 variant+ND2 variant group was higher than those rates in the BAR-3 normal+ND2 variant, BAR-3 normal+ND2 normal. The BAR-3 normal+ND2 variant group preferred much carbohydrate and less animal protein compared with other three groups. A combination of SNPs of the nuclear BAR-3 and the mitochondrial ND2 genes may affect eating behavior besides the biochemical and metabolic process of signal transduction and electron transfer system.