title: Fitness change effects on midlife metabolic outcomes.
abstract: OBJECTIVE
  Fitness decline, high body mass index (BMI), and insulin resistance (IR) are associated with worsening cardiometabolic risk factors prospectively; modification of the fitness change effect by BMI and IR remains unknown.
  
  
  METHODS
  Participants from the Coronary Artery Risk Development in Young Adults study without diabetes at year 0 (Y0) (n = 2048, 43.4% men; mean age, 25 yr) had fitness quantified by treadmill at Y0 and Y20. Y0 BMI was normal (nBMI <25 kg·m) or high (hBMI ≥25 kg·m). Y0 IR status was insulin sensitive (IS) (homeostatic model assessment IR <1.84 (75th percentile)) or insulin resistant (IR) (homeostatic model assessment IR ≥1.84). Four groups were established: nBMI/IS, hBMI/IS, nBMI/IR, and hBMI/IR. Y0 fitness was low (<33rd percentile for sex) or average high (≥33rd percentile for sex). Fitness change (treadmill time: Y20-Y0) was maintained (increase or decline ≤20th percentile for sex) or decreased (decline >20th percentile for sex). The outcomes were incident diabetes and percentage change over 25 yr in weight, waist girth, blood pressure, and lipid profile. Analysis was by multiple linear regression and proportional hazards regression with adjustment for individual characteristics.
  
  
  RESULTS
  Maintained fitness after 20 yr was associated with greater increase in HDL cholesterol and less increase in weight, waist girth, blood pressure, and triglycerides than decreased fitness, similarly for the groups defined by BMI and IR. Maintained fitness reduced the rate of incident diabetes in IS but not IR participants.
  
  
  CONCLUSIONS
  Maintained fitness after 20 yr was associated with more favorable middle-age cardiometabolic risk factors than decreased fitness; this benefit might be blunted by baseline IR.
authors.affiliation: 1University of Minnesota, Minneapolis, MN; 2Northwestern University, Evanston, IL; 3Pennington Biomedical Research Center, Baton Rouge, LA; and 4Kaiser Permanente Division of Research, Oakland, CA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Chow
authors.forename: Lynn E
authors.initials: LE
authors.lastname: Eberly
authors.forename: Erin
authors.initials: E
authors.lastname: Austin
authors.forename: Mercedes
authors.initials: M
authors.lastname: Carnethon
authors.forename: Claude
authors.initials: C
authors.lastname: Bouchard
authors.forename: Barbara
authors.initials: B
authors.lastname: Sternfeld
authors.forename: N A
authors.initials: NA
authors.lastname: Zhu
authors.forename: Steve
authors.initials: S
authors.lastname: Sidney
authors.forename: Pamela
authors.initials: P
authors.lastname: Schreiner
mesh_terms: D000293:Adolescent; D000328:Adult; D001794:Blood Pressure; D015992:Body Mass Index; D008076:Cholesterol, HDL / Q000097:blood; D003327:Coronary Disease / Q000453:epidemiology; D003920:Diabetes Mellitus / Q000453:epidemiology; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008137:Longitudinal Studies; D008297:Male; D010809:Physical Fitness; D011446:Prospective Studies; D012307:Risk Factors; D014280:Triglycerides / Q000097:blood; D055105:Waist Circumference; D015430:Weight Gain; D055815:Young Adult
chemical_list: D008076:Cholesterol, HDL; D014280:Triglycerides