Does meeting physical activity guidelines in normal weight females influence body fatness? : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand

Abstract

Purpose: To investigate the associations among objectively measured physical activity and markers of body composition in normal weight, New Zealand European women.

Methods: Anthropometric measures were performed in 107 women aged 16-45 years with a BMI between 18.5 to 25 kg/m2. Accelerometers were worn over 7 days to assess sedentary time (<100 counts per minute), light (100 - 2019), moderate (2200 - 5998) and vigorous (>5999) physical activity. Independent t-tests were used to compare associations between participants with normal (<30%) and high (=30%) body fat. Partial correlations examined the independent associations of physical activity behaviours on body fat.

Results: Participants with normal body fat completed significantly more moderate to vigorous physical activity (MVPA) minutes per week (P = .002) and MVPA% (P =.021). Achieving current physical activity recommendations of = 150 mins/week of MVPA, resulted in lower body fat (P =.038). Achieving =300 mins/week of moderate physical activity showed a trend towards significance for lower body fat (P = .076), while achieving =150 mins/week of vigorous activity showed significantly lower body fat% (P = .022). Partial correlations determined the significance of MVPA on body fat% independent of sedentary (r [104] = -.258 P = 0.008) and light activity (r [104] = -.273 P = 0.005).

Conclusion: Achieving current exercise recommendations was associated with lower body fat % in normal weight women. Our data suggest this association is stronger for vigorous activity, and is independent of the amount of sedentary activity achieved. Increasing vigorous physical activity may be important for improving body composition in this group.