Low cardiorespiratory fitness (CRF) is associated with an increased risk of developing abdominal obesity (AO), but it is not known if and/or how changes in CRF affect AO. We examined the relationship between changes in CRF and the risk of developing AO. This is a retrospective observational study of a cohort of 1883 sedentary patients, who had participated in a clinical trial of physical activity promotion carried out in Spain (2003-2007). These data were not used in the clinical trial. At baseline, they were free of cardiovascular disease, hypertension, diabetes, dyslipidemia, and/or AO; with an indirect VO2max measurement; 19-80 years old; and 62% were women. All the measures were repeated at 6, 12, and 24 months. The exposure factor was the change in CRF at 6 or 12 months, categorized in these groups: unfit-unfit, unfit-fit, fit-unfit, and fit-fit. We considered fit and unfit participants as those with VO2max values in the high tertile, and in the moderate or low tertiles, respectively. The main outcome measure was the risk of developing AO at one and two years, as defined by waist circumference >102 (men) and >88 (women) cm. At two years, 10.5% of the participants had developed AO: 13.5% in the unfit-unfit group of change at 6 months; 10.3% in the unfit-fit group (adjusted odds ratio (AOR) 0.86; 95% confidence interval (CI) 0.49-1.52); 2.6% in the fit-unfit group (AOR 0.13; 95%CI 0.03-0.61); and 6.0% in the fit-fit group (AOR 0.47; 95%CI 0.26-0.84). Those who stayed fit at 6 months decreased the probability of developing abdominal obesity at two years.
Keywords: cardiorespiratory fitness; cumulative incidence; health correlates; obesity; primary health care; waist circumference.