Cardiorespiratory fitness as a Determinant Factor for the 30% of Obese Individuals That are Metabolically Healthy

Previous studies have shown that individuals can be obese and metabolically healthy, or of normal weight with an unhealthy metabolic profile. The metabolically healthy obese (MHO) phenotype currently represents 30% of obese individuals. However, major studies have so far failed to consider the possible impact of cardiorespiratory fitness on metabolic health.

MHO individuals are characterised by having low abdominal adiposity, low inflammation level and low risk of developing metabolic comorbidity. This study hypothesised that cardiorespiratory fitness, is a determinant factor for the MHO phenotype. It aimed to investigate the associations between fitness, abdominal adiposity and low-grade inflammation within different BMI categories. Data from 10,976 individuals on waist circumference (a surrogate measurement for abdominal adiposity), cardiorespiratory fitness and C-reactive protein levels (a measure of low-grade inflammation) were analysed.

In both men and women, this study found a strong inverse association between fitness and waist circumference adjusted for age, education, smoking, alcohol and BMI. It also found that fitness reduced levels of inflammation regardless of BMI. Furthermore, a positive association between waist circumference and C-reactive protein, in both men and women in all BMI categories. This study demonstrates that there is a considerable difference in the values for abdominal adiposity, fitness and low-grade inflammation in people with the same BMI. Therefore, in order for clinicians to obtain a more accurate identification of individuals who are healthy despite obesity and individuals who are at metabolic risk despite the normal weight, additional measurements of waist circumference, CRP and fitness should be taken in to account.