title: Assessment of physical activity level in relation to obesity: current evidence and research issues.
abstract: OBJECTIVE
  Validations of methods for the assessment of physical activity and studies on the relation between energy expenditure of activity and obesity were reviewed, with suggestions for further research.
  
  
  METHODS
  Validation studies of field methods for the assessment of physical activity against doubly labeled water were evaluated, studies on the relation between doubly labeled water assessed energy expenditure of activity and obesity are discussed.
  
  
  METHODS
  Three field methods for the assessment of physical activity, validated with doubly labeled water as a criterion method, were included: activity questionnaires, heart rate monitoring, and motion sensors.
  
  
  RESULTS
  The triaxial accelerometer came out as the best field method for the assessment of physical activity, followed by the Baecke activity questionnaire. The majority of obese subjects are moderately active, and an increase in the activity level of obese subjects is limited by the ability to perform exercise of higher intensity.
  
  
  CONCLUSIONS
  Accelerometers are an objective tool for the assessment of physical activity in large populations over periods long enough to be representative for normal daily life and with minimal discomfort to the subjects. The accelerometer can be used to distinguish differences in activity levels between individuals and to assess the effect of interventions on physical activity within individuals.
authors.affiliation: Department of Human Biology, Maastricht University, The Netherlands. K.Westerterp@HB.Unimaas.NL
authors.forename: K R
authors.initials: KR
authors.lastname: Westerterp
mesh_terms: D003903:Deuterium; D004734:Energy Metabolism; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D009765:Obesity / Q000503:physiopathology*; D005082:Physical Exertion / Q000502:physiology*; D015203:Reproducibility of Results; D012621:Seasons; D011795:Surveys and Questionnaires
chemical_list: D003903:Deuterium