Fat versus Fit


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Fat versus Fit

  1. 1. Cardiorespiratory Fitness and Adiposity as Mortality Predictors in Older Adults JAMA December 5, 2007
  2. 2. Background <ul><li>32% of Americans are obese </li></ul><ul><li>Obesity is associated with a number of health problems </li></ul><ul><li>Vast majority of people do not exercise </li></ul><ul><li>These trends worsen with aging </li></ul><ul><li>There is little data regarding associations among obesity, physical activity and mortality </li></ul><ul><li>What is more important, fat or fitness? </li></ul>
  3. 3. Methods <ul><li>Objective: determine the association among cardiorespiratory fitness, adiposity and mortality on older adults </li></ul><ul><li>Cohort Study: prospective study of 2,603 adults > 60 yrs </li></ul><ul><ul><li>Had to achieve 85% HR on treadmill test to be included </li></ul></ul><ul><ul><li>Patients grouped into quintiles based on duration of test </li></ul></ul><ul><ul><li>Also grouped by BMI, waist circumference, body fat % and fat free mass </li></ul></ul><ul><li>Patients completed a comprehensive health evaluation, physical exam, blood lipids and glucose and EKG </li></ul>
  4. 4. Methods Cont. <ul><li>Used METS (metabolic equivalent tasks) based on treadmill speed and grade to standardize interpretation </li></ul><ul><li>Outcome was all-cause mortality </li></ul><ul><li>Multivariate analysis performed using age, sex, exam year, smoking, abnormal exercise EKG and chronic medical conditions </li></ul>
  5. 5. Results
  6. 6. <ul><li>Table I - Highlights </li></ul><ul><li>20% women </li></ul><ul><li>BMI and waist circumference was the same for both groups </li></ul><ul><li>Treadmill time was 2 minutes less in decedents </li></ul><ul><li>HDL was 4 pts higher in survivors, as was incidence of hypercholesterolemia </li></ul><ul><li>Smoking was 5% more prevalent in decedents </li></ul>
  7. 7. <ul><li>Table II - Highlights </li></ul><ul><li>Opposing trend in fitness quintile for lowest and highest BMI groups </li></ul><ul><li>HDL directly correlated w/ fitness quintile </li></ul><ul><li>Except in lowest quintile, smoking inversely correlated w/ fitness </li></ul><ul><li>Except in highest quintile, hypertension and cholesterol directly correlated w/ fitness </li></ul><ul><li>One BMI > 35 actually made it 18 minutes </li></ul>
  8. 8. <ul><li>Table IV - Highlights </li></ul><ul><li>J-shaped relationship between BMI and mortality </li></ul><ul><li>EKG changes, chronic medical conditions and waist circumference correlate w/ mortality </li></ul><ul><li>Percent body fat and fat free mass did not </li></ul>
  9. 9. Table V <ul><li>Hazard ratios for fitness and adiposity -> results show better fitness = better mortality </li></ul><ul><li>Initially adjusted for 1) age, sex, EKG changes, smoking, exam year and medical conditions </li></ul><ul><li>Additional adjustments for 2) BMI, 3) waist circumference, 4) percent body fat and 5) fat-free mass did not change the results </li></ul>
  10. 10. Study Limitations <ul><li>Cohort -> possibility of confounders </li></ul><ul><li>Homogeneous study group (white, educated, middle and upper class) </li></ul><ul><li>No info about diet or medication use </li></ul><ul><li>Fitness tested only once at outset of study </li></ul><ul><li>Does not really address association between a spot fitness check and daily cardiovascular exercise </li></ul><ul><li>Small number of women and few deaths within this group </li></ul>
  11. 11. Conclusions <ul><li>Fitness is a strong predictor of overall mortality independent of body composition </li></ul><ul><li>Assuming an otherwise healthy individual, there is no association betw abdominal obesity and mortality when adjusted for fitness </li></ul><ul><li>Fit individuals who are obese had lower mortality than unfit normal-weight or lean individuals </li></ul><ul><li>Fat distribution and frame size may be more important than adiposity </li></ul><ul><li>There is a J-shaped relationship betw BMI and mortality, both before and after adjusting for fitness </li></ul>
  12. 12. FIN