The relationship between serum leptin concentration and the percentage of body fat in Japanese high school students.

Leptin is a hormone that is synthesized and secreted by adipocytes. Leptin has been found to participate in a number of regulatory physiological functions. It suppresses food intake and increases energy consumption, increases blood pressure, and improves carbohydrate metabolism. The relationship between serum leptin concentration and percentage of body fat (% BF) in Japanese students in the 1st year of high school (1stHS, n = 889) and the 3rd year of high school (3rdHS, n = 948) was examined in a cross-sectional study. The mean of serum leptin concentrations showed no significant difference between the 1stHS and 3rdHS; it was significantly higher in girls than in boys in both grades. Significant gender differences were observed in both the slope and intercept of the regression lines. These results suggest that the serum leptin concentrations in Japanese high-school students do not differ significantly in the 1stHS and 3rdHS, but change with % BF, regardless of school year and the presence or absence of obesity.

[Relationship between the number of steps taken and body mass index for male workers in the metropolitan area].

The present study examined the relationship between number of steps and body mass index (BMI) among male workers in the metropolitan area. The number of subjects were 310 (aged 30-59) and they were studied for seven consecutive days. The number of steps was measured by a pedometer. Energy expenditure was assessed by the activity record method. Energy intake was assessed by a food frequency questionnaire. Height and body weight were examined by a self-administered questionnaire. BMI of 81 subjects (26.1%) was greater than 25 kg/m2. The number of steps was 10,682 +/- 4,365 on working days, and 7,135 +/- 4,536 on holidays. Average energy expenditure in seven days was 2,259 +/- 378 kcal/d. The physical activity level (PAL) was 1.5 +/- 0.1. There was a significant correlation between BMI and the number of steps in a working day (r=-0.188, p<0.01). In addition, there were significant correlations between PAL and daily steps on working days (r=0.301, p<0.001), and on holidays (r=0.296, p<0.001). Subjects were divided into four groups according to the median number of steps on working days and energy intake (I; > or =9,894 steps, <1,901 kcal, II; > or =9,894 steps, > or =1,901 kcal, III; <9,894 steps, <1,901 kcal, IV; <9,894 steps, > or =1,901 kcal). BMI of Group IV (24.7 kg/m2) was significantly higher than that of the other Groups. Group III had the highest proportion of subjects (15.7%) with lifestyle related diseases.