title: Determining the amount of physical activity needed for long-term weight control.
abstract: OBJECTIVE
  To evaluate prospectively the influence of habitual physical activity on body weight of men and women and to develop a model that defines the role of physical activity on longitudinal weight change.
  
  
  METHODS
  Occupational cohort study conducted for a mean of 5.5 y.
  
  
  METHODS
  A total of 496 (341 male and 155 female) NASA/Johnson Space Center employees who completed the 3 month education component of the employee health-related fitness program and remained involved for a minimum of 2 y.
  
  
  METHODS
  Body weights were measured at baseline (T1) and follow-up (T2), and habitual physical activity was obtained from the mean of multiple ratings of the 11-point (0-10) NASA Activity Scale (NAS) recorded quarterly between T1 and T2. Other measures included age, gender, VO(2 max) obtained from maximal treadmill testing, body mass index (BMI), and body fat percentage.
  
  
  RESULTS
  Multiple regression demonstrated that mean NAS, T1 weight, aging and gender all influence long-term T2 weight. T1 age was significant for the men only. Independently, each increase in mean NAS significantly (P<0.01) reduced T2 weight in men (b=-0.91 kg; 95% CI:-1.4 to-0.42 kg) and women (b=-2.14 kg; 95% CI:-2.93 to-1.35 kg). Mean NAS had a greater effect on T2 weight as T1 weight increased, and the relationship was dose-dependent.
  
  
  CONCLUSIONS
  Habitual physical activity is a significant source of long-term weight change. The use of self-reported activity level is helpful in predicting long-term weight changes and may be used by health care professionals when counseling patients about the value of physical activity for weight control.
authors.affiliation: Health-Related Fitness, NASA/Johnson Space Center, Houston, Texas 77058, USA. larry.t.wier1@jsc.nasa.gov
authors.forename: L T
authors.initials: LT
authors.lastname: Wier
authors.forename: G W
authors.initials: GW
authors.lastname: Ayers
authors.forename: A S
authors.initials: AS
authors.lastname: Jackson
authors.forename: A C
authors.initials: AC
authors.lastname: Rossum
authors.forename: W S
authors.initials: WS
authors.lastname: Poston
authors.forename: J P
authors.initials: JP
authors.lastname: Foreyt
mesh_terms: D000328:Adult; D000375:Aging; D015992:Body Mass Index; D001835:Body Weight; D015331:Cohort Studies; D015444:Exercise; D005260:Female; D006184:Habits; D006801:Humans; D007899:Leisure Activities; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011446:Prospective Studies