cardiorespiratory fitness and mortality

Doug Skrecky (oberon@vcn.bc.ca)
Wed, 4 Aug 1999 03:45:39 -0700 (PDT)

Authors
Lee CD. Blair SN. Jackson AS.
Institution
Division of Epidemiology & Clinical Applications, Cooper Institute for Aerobics Research, Dallas, TX, USA.
Title
Cardiorespiratory fitness, body
composition, and all-cause and cardiovascular disease mortality in men. Source
American Journal of Clinical Nutrition. 69(3):373-80, 1999 Mar. Abstract
BACKGROUND: Cardiorespiratory fitness and body fatness are both related to health, but their interrelation to all-cause and cardiovascular disease (CVD) mortality is unknown. OBJECTIVE: We examined the health benefits of leanness and the hazards of obesity while simultaneously considering cardiorespiratory fitness. DESIGN: This was an observational cohort study. We followed 21925 men, aged 30-83 y, who had a body-composition assessment and a maximal treadmill exercise test. There were 428 deaths (144 from CVD, 143 from cancer, and 141 from other causes) in an average of 8 y of follow-up (176742 man-years). RESULTS: After adjustment for age, examination year, cigarette smoking, alcohol intake, and parental history of ischemic heart disease, unfit (low cardiorespiratory
fitness as determined by maximal exercise testing), lean men had double the risk of all-cause mortality of fit, lean men (relative risk: 2.07; 95% CI: 1.16, 3.69; P = 0.01). Unfit, lean men also had a higher risk of all-cause and CVD mortality than did men who were fit and obese. We observed similar results for fat and fat-free mass in relation to mortality. Unfit men had a higher risk of all-cause and CVD mortality than did fit men in all fat and fat-free mass categories. Similarly, unfit men with low waist girths (<87 cm) had greater risk of all-cause mortality than did fit men with high waist girths (> or =99 cm). CONCLUSIONS: The health benefits of leanness are limited to fit men, and being fit may reduce the hazards of obesity.

Additional quotes from the above research paper:

"The all-cause mortality rate of fit, obese men was not significantly
different from that of fit, lean men."

Table 3 

 Waist circumference category                Multivariate RR
 and cardiorespiratory fitness level           of death

 Low waist circumference (<87 cm)
  Fit                                              1.0
  Unfit                                            4.88
 Moderate waist circumference (87 to <99 cm)
  Fit                                              1.05
  Unfit                                            2.05
 High waist circumference (>99 cm)
  Fit                                              0.95
  Unfit                                            2.40

"In summary, we found that obesity did not appear to increase mortality
risk in fit men. For long-term health benefits we should focus on improving fitness by increasing physical activity rather than relying only on diet for weight control. Aerobic exercise improves IHD risk factors, and increases in physical activity or fitness extend longevity. Although some studies show that there is no difference between diet and aerobic exercise in reducing IHD risk factors, or even report that diet is better than aerobic exercise for improving IHD risk factors in overweight men, our data show that fit men had greater longevity than unfit men regardless of their body composition or risk factor status. Obese men should be encouraged to increase their cardiorespiratory fitness by engaging in regular, moderate intensity physical activity; this should benefit them even if they remain overweight."

Additional note by poster:

Although weight loss through dieting is associated with improvements in some IHD risk factors, what is not widely recognized is that other IHD risk factors are worsened. These include increased homocysteine, lower HDL, and reductions in intake of heart protective omega-3 fatty acids, and possibly reduced dietary arginine (nut) intake. These are some of the factors that may explain why most studies have found that dieting does not lower mortality rates.
Although this is not a popular idea, body fatness in and of itself appears to be neutral with respect to mortality. Other variables are the key determining factors of human life expectancy, and cardiorespiratory fitness as measured by a treadmill is one.