title: Energy cost of physical activities in 12-y-old girls: MET values and the influence of body weight.
abstract: BACKGROUND
  Few data exist on the energy cost of specific activities in children. The influence of body weight on the energy cost of activity when expressed as metabolic equivalents (METs) has not been vigorously explored.
  
  
  OBJECTIVE
  To provide MET data on five specific activities in 12-y-old girls and to test the hypothesis that measured MET values are independent of body weight.
  
  
  METHODS
  In 17 12-y-old girls, resting metabolic rate (RMR) and the energy expended while sitting, standing, walking on a flat treadmill at 3.2 and at 4.8 km/h, and walking on a treadmill at a 10% incline at 4.8 km/h were measured using indirect calorimetry. MET values were calculated by dividing the energy expenditure of an activity by the subject's RMR. The influence of body weight was assessed using simple linear regression.
  
  
  RESULTS
  The observed METs were more consistent with published values for similar activities in adults than those offered for children. Body weight was a statistically significant predictor of the MET of all three walking activities, but not the MET of sitting or standing. Body weight explained 25% of the variance in the MET value for walking at 3.2 km/h, 39% for walking at 4.8 km/h, and 63% for walking at a 10% incline at 4.8 km/h.
  
  
  CONCLUSIONS
  METs for the three walking activities were not independent of body weight. The use of average MET values to estimate the energy cost of these three activities would result in an underestimation of their energy cost in heavier girls and an overestimation in lighter girls. These results suggest that the estimation of total energy expenditure from activity diary, recall, and direct observation data using average MET values may be biased by body weight.
authors.affiliation: General Clinical Research Center, Massachusetts Institute of Technology, Cambridge, MA, USA. jennifer.spadano@tufts.edu
authors.forename: J L
authors.initials: JL
authors.lastname: Spadano
authors.forename: A
authors.initials: A
authors.lastname: Must
authors.forename: L G
authors.initials: LG
authors.lastname: Bandini
authors.forename: G E
authors.initials: GE
authors.lastname: Dallal
authors.forename: W H
authors.initials: WH
authors.lastname: Dietz
mesh_terms: D001481:Basal Metabolism / Q000502:physiology; D001835:Body Weight / Q000502:physiology*; D002648:Child; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D009043:Motor Activity / Q000502:physiology*; D011446:Prospective Studies