65 second the employees mean rating was used as a

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> 6.5. Second, the employee’s mean rating was used as a continuous variable for data analysis. While the rating was self-report, previous research has established the scale’s validity. 22,23 Statistical analysis Analysis of variance (ANOVA) was used to evaluate gender differences on all variables studied. Multivariate analysis of variance (MANOVA) was used to study changes in body weight for gender and level of physical activity that occurred between T1 and T2. Wilks’ lambda was the MANOVA test for significance. The Wilks’ lambda procedure, which examines the multivariate dispersion among all of the groups of vari- ables, is favored by statisticians because it is derived by the maximum likelihood technique. 26 Multiple regression was used as a post hoc analysis to: (1) define the independent Amount of activity for weight control LT Wier et al 614 International Journal of Obesity
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influence of physical activity on longitudinal weight change; and (2) provide an empirical model to define the level of physical activity needed for weight control. The dependent variable was T2 weight. The independent variables were T1 weight, T1 age, time differences between T1 and T2 tests (ie aging), and mean NAS. Results Table 1 gives the subject baseline characteristics contrasted by gender. The males were significantly older than the females, the difference being 6 y. The men and women differed significantly on height, weight, BMI, percentage body fat and VO 2max . These are well-documented gender differences. When broken into age groups the weight and BMI of the men and women in this sample were very similar to large national samples, such as the third National Health and Nutrition Examination Survey (NHANES III). 5 Using the American College of Sports Medicine standards, 27 the men were in the average aerobic fitness and body fat categories for their age group; the women were average in aerobic fitness, but slightly poorer than average in body composition. The NAS at T1 was slightly, but significantly greater for the men. The mean NAS shows both the men and women increased their level of physical activity once they entered the fitness program and the significant gender difference in physical activity remained. Table 1 Baseline (T1) characteristics of the NASA occupational cohort by gender Variable Men ( n 341) Women ( n 155) F Age (y) 42.1 ± 10.1 36.1 ± 10.6 36.39* Height (cm) 177.8 ± 6.6 165.1 ± 6.3 409.34* Weight (kg) 82.2 ± 12.2 67.0 ± 13.5 154.77* BMI (kg = m 2 ) 25.9 ± 3.5 24.4 ± 4.4 16.15* Percentage body fat (%) 21.9 ± 5.8 29.3 ± 6.1 168.35* VO 2max (ml = kg = min) 38.6 ± 8.1 32.5 ± 7.5 63.22* Baseline (T1) NAS (0 – 10) 3.8 ± 2.1 3.3 ± 1.9 6.55* Mean NAS 5.6 ± 1.2 5.0 ± 1.2 28.76* Note: NAS self-reported physical activity. * P < 0.01. Table 2 Male and female body weights (kg) at T1 and T2 contrasted by level of physical activity Men ( n 341) Women ( n 155) Variable n T1 T2 n T1 T2 Total sample 341 82.2 ± 12.2 82.6 ± 12.2 155 67.0 ± 13.5 68.4 ± 12.2 Inactive 13 88.5 ± 15.0 90.2 ± 17.1 15 68.8 ± 15.9 77.6 ± 21.0 Moderately active 79 85.2 ± 13.0 86.5 ± 12.6 51 68.8 ± 15.0 69.9 ± 15.4 Active 186 81.6 ± 11.7 82.1 ± 11.6 78 65.9 ± 11.9 66.6 ± 10.3 Very active 63 79.1 ± 10.8 77.8 ± 10.5 11 64.5 ± 14.9 61.4 ± 9.8 Figure 1 Mean changes ( ± 95% CI) in body weight ( D T2 7 T1) contrasted by activity group.
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  • Spring '12
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