title: Body composition is associated with physical activity in daily life as measured using a triaxial accelerometer in both men and women.
abstract: BACKGROUND
  Activity-related energy expenditure is the most variable component of total energy expenditure and thus an important determinant of energy balance.
  
  
  OBJECTIVE
  To determine whether body composition is related to physical activity in both men and women.
  
  
  METHODS
  A total of 134 healthy participants were recruited (80 women, 54 men; aged 21+/-2 years; body mass index, 22.0+/-2.4). Physical activity was measured for a period of 2 weeks using a triaxial accelerometer for movement registration (Tracmor). Percentage body fat (%BF) was determined by underwater weighing and deuterium dilution according to Siri's three-compartment model.
  
  
  RESULTS
  The participant characteristics-body mass, height and gender together explained a substantial part of the variation in %BF (R(2)=0.75, SEE=4.0%). Adding physical activity to the model increased the explained variation in %BF with 4% (R(2)=0.79, SEE=3.7%, P<0.001). Taking seasonality into account by adding the number of daylight hours as an independent variable further increased the explained variation with 1% (R(2)=0.80, SEE=3.7%, P<0.05). In analogy, the association was evaluated for both genders separately. In women, %BF and physical activity were significantly associated (P<0.001). In men, %BF was only associated with physical activity when seasonality was taken into account as well (P<0.05). This probably resulted from men participating more in season bound sports, because an association was found without adjusting for seasonality when only men with a consistent year-round participation in sports were considered.
  
  
  CONCLUSIONS
  Evidence was found for an association between body composition and physical activity in both genders. A consistent year-round degree of physical activity appears to be a prerequisite to reveal the association. Moreover, Tracmor-assessed physical activity improves the estimate of %BF when a participant's characteristics are taken into account.
authors.affiliation: Department of Human Biology, Maastricht University, Maastricht, The Netherlands. m.denhoed@hb.unimaas.nl
authors.forename: M
authors.initials: M
authors.lastname: den Hoed
authors.forename: K R
authors.initials: KR
authors.lastname: Westerterp
mesh_terms: D000054:Acceleration; D000273:Adipose Tissue / Q000033:anatomy & histology; D001823:Body Composition / Q000502:physiology*; D001827:Body Height / Q000502:physiology; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D012621:Seasons; D012737:Sex Factors; D055815:Young Adult