A study published in the International Journal of Epidemiology has challenged the current concept that by being physically fit, individuals who are obese can fully compensate mortality risk. The study suggests that physically fit obese men are at higher risk for death than men who are of normal weight but are physically unfit. And it also found a graded association between aerobic fitness at the age of 18 years and the risk of early death.

The study by Gabriel Högström, PhD, a postgraduate student in the Dept. of Community Medicine and Rehabilitation at Umeå University, Sweden, and colleagues, drew data from the Swedish Military Conscription Registry and included 1,317,713 Swedish men (mean age, 18 years) conscripted into the Swedish military between 1969 and 1996. At the time of conscription, the men underwent baseline assessments that included aerobic fitness testing, in which they cycled until fatigue caused them to stop. The researchers looked at all-cause and cause-specific deaths, using national registers. Mortality information came from the National Cause of Death Registry.

During a mean follow-up of 28.8 years, 44,301 of the men died. After adjusting for age and conscription year, men with the highest aerobic fitness levels had 51% lower risk for all-cause death (hazard ratio [HR], 0.49; 95% confidence interval [CI], 0.47 - 0.51vs those with the lowest fitness levels. Similar findings resulted from analyses of weight-adjusted fitness (HR, 0.52; 95% CI, 0.50 - 0.54).

Alcohol and narcotic abuse had the strongest associations with death (HR, 0.20; 95% CI, 0.15 - 0.26).

Obese men benefited less than normal-weight men from being physically fit (P < .001). Normal-weight men in all levels of aerobic fitness had lower risk for all-cause mortality (30% - 48%; P < .05 for all) compared with obese men with the highest levels of aerobic fitness.

The benefits of aerobic fitness decreased as weight increased. After adjusting for age and year, normal-weight men in the upper half of aerobic fitness had 34% lower risk for death than those in the lower half (HR, 0.66; 95% CI, 0.64 - 0.68). This benefit decreased to 28% in overweight men, and disappeared entirely in men with the highest levels of obesity… (Medscape)