Cardio-respiratory fitness and metabolic syndrome

April 03' 2020

Moderate physical activity has enormous public health implications on metabolic syndrome, CVD and type 2 diabetes.

Metabolic syndrome is defined as a conglomeration of risk factors known to be associated with increased risk of both atherosclerosis, cardiovascular disease and type 2 diabetes.

Risk factors

Excessive weight (obesity) and lack of physical activity are two of the major factors associated with increasing metabolic syndrome risks. These two factors are increasing in both U.S. adults and children. Understanding how weight gain and lack of physical activity are associated with increased metabolic syndrome and CVD mobility and mortality are major public problems. Most studies have shown that increases iin physical activity are associated with lower rates of metabolic syndrome and other CVD comorbid conditions.

Most importantly, there is an inverse relationship between metabolic syndrome and sedentary lifestyle. In fact, Ford et al studied the association between self-reported physical activity and prevalence of metabolic syndrome in the NHANES data. They demonstrated that adults who engaged in > 4 hours of sedentary behavior had higher prevalence of metabolic syndrome, whereas those who engaged in more self-reported activity had less metabolic syndrome. These studies, clearly demonstrated enormous CVD benefits of increased physical activity in lowering incidence of metabolic syndrome.

The relationships between physical activity and metabolic syndrome incidence and prevalence have been inconsistent in the literature. This may be due to the self-report nature of physical activity, especially in women in most previous studies. This issue is particularly important in black women who report less leisure time physical activity compared to white women. Cardio-respiratory fitness is best measured by maximal exercise stress test or VO2max test. This form of testing is a more reliable measure of physical activity and is less prone to underreporting than self-report.

Low levels of cardio-respiratory fitness were a strong and independent risk factor for metabolic syndrome. They compared subjects in the lowest third for cardiorespiratory fitness and found that the risk of developing metabolic syndrome was 20% to 26% lower among participants in the middle third and 53% to 63% lower among those in the highest third. Their study clearly demonstrated the protective effects of cardio-respiratory fitness on development of metabolic syndrome. In another study, low levels of cardio-respiratory fitness to be associated with higher all-cause mortality in men and women.

Finally, the interaction between VO2max and metabolic risk factors for CVD in women has been less studied, especially in black women. Black women at every age strata reported less leisure time physical activity when compared to white women and Hispanic women. Ironically, despite the lower level of reported physical activity and greater insulin resistance, black women have lower incidence of metabolic syndrome when compared to white women. This has been partly attributed to the higher serum HDL and lower triglycerides in black women than white women. Therefore, there is a disconnect in the relationship between metabolic syndrome and self-report leisure time physical activity in black women and other high risk ethnic populations.

In summary, higher levels of cardio-respiratory fitness and physical activity are associated with lower rates of metabolic syndrome as well as decreases in CVD and coronary heart disease. Therefore, there is a need for health care professionals to encourage moderate physical activity to all person regardless of obesity. We conclude, thus physical activity (albeit modest) has enormous public health implications on metabolic syndrome, CVD and type 2 diabetes in the general population.