The 20-40 RULE in Fitness and Disease

July 13, 2009

My 20-40 rule:

A low fitness level in your teens translate to a high level of risk for developing diabetes by age 40! 

That’s the message I got from this study published in Diabetes Care called the CARDIA Fitness Study.

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Objective: Test the association of fitness changes over 7- and 20-years on the development of diabetes in middle-age.

Research Design and Methods: Fitness was determined based on the duration of a maximal graded exercise treadmill test (Balke protocol) at up to three examinations over 20-years from 3989 black and white men and women from the Coronary Artery Risk Development in Young Adults study. Relative fitness change (%) was calculated as the difference between baseline and follow-up treadmill duration/baseline treadmill duration. Diabetes was identified as fasting glucose ≥126 mg/dL, post-load glucose ≥200 mg/dL, or use of diabetes medications.

Results:

  • Diabetes developed at a rate of 4 per 1000 person-years in women (n=149) and men (n=122) and lower baseline fitness was associated with a higher incidence of diabetes in all race-sex groups (hazard ratios from 1.8 to 2.3).
  •  On average, fitness declined 7.6% in women and 9.2% in men over 7 years.
  • The likelihood of developing diabetes increased per standard deviation decrease (19%) from the 7-year population mean change (−8.3%) was in women (hazard ratio [HR]=1.22, 95% CI: 1.09, 1.39) and men (HR=1.45, 95% CI: 1.20, 1.75) following adjustment for age, race, smoking, family history of diabetes, baseline fitness, body mass index (BMI), and fasting glucose.
  • Participants who developed diabetes over 20 years experienced significantly larger declines in relative fitness over 20 years vs those who did not..

Conclusions: Low fitness is significantly associated with diabetes incidence and explained in large part by the relationship between fitness and BMI.

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This study shows that inidviduals risk to develop lifestyle related diseases especially diabetes are at increasing overtime depending on the level of fitness:

  • Women were at 22% increased risk of developing diabetes
  • men were at a 45% increased risk…

 for every standard deviation decrease from the mean fitness change.  This relationship continued to exists even after adjusting for age, smoking, family history of diabetes, and baseline fasting glucose.  In fact the researchers noted that the baseline BMI was a better predictor for developing diabetes than the baseline fasting glucose as well as baseline fitness.

What Do These Data MEAN?

  • If two individuals have similar fitness level; the bigger person with a higher BMI is more likely to develop diabetes than the smaller frame guy overtime in the next 10-20 years.
  •  The possible mechanism by which fitness decreases risk for diabetes is most likely related to the regulation of body mass.  A lower BMI means better insulin sensitivity and less production of toxic substances by increased adiposity that can lead to further cardiovascular complications associated with obesity and diabetes. 

The authors conlcuded:

That regular physical activity to “improve and maintain cardiorespiratory fitness is an important component of a healthy lifestyle.” 

 AMEN!

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4 Responses to “The 20-40 RULE in Fitness and Disease”

  1. Treadmill Says:

    Interesting thoughts. I’ve never heard this before.


  2. […] Doc Gerry wrote an interesting post today onThe 20-40 RULE in <b>Fitness</b> and Disease « That Health RulesHere’s a quick excerpt […]

  3. Devon Says:

    I really like your blog and i respect your work. I’ll be a frequent visitor.

  4. Treadmill Says:

    Here’s some more science on the relationship between fitness and diabetes — http://www.treadmill-world.com/benefit-cardiovascular-exercise.html


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