Both Improving Fitness and Preventing Fat Gain Important in Reducing Risk of Cardiovascular Disease

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Both Improving Fitness and Preventing Fat Gain Important in Reducing Risk of Cardiovascular Disease
Study finds that a positive change in fitness and fatness leads to less hypertension, metabolic syndrome and hypercholesterolemia
Maintaining or improving fitness, as well as preventing fat gain, are associated with a lower probability of developing risk factors for cardiovascular disease (CVD) in healthy adults, according to a study published in the February 14, 2012, issue of the Journal of the American College of Cardiology (JACC).  The study is one of the first to examine how a change in fitness or fatness (or both) affects subsequent development of CVD risk factors.
Seeking to provide a more targeted look at how changes in fitness and fatness affect heart health, a U.S. research team examined these two variables in 3,148 healthy adults across three medical examinations.  The Aerobics Center Longitudinal Study (ACLS) enrolled healthy men and women between 1979 and 2006, analyzing how their fitness and fatness levels changed over time and how that related to the subsequent development of hypertension, metabolic syndrome and hypercholesterolemia—all risk factors for cardiovascular disease. The first exam was used for baseline data, while the second was used to determine a change in fitness or fatness over a mean period of 2.1 years. The third exam analyzed the incidence of the CVD risk factors over an average 6-year follow-up from the second examination.  
Cardiorespiratory fitness was determined through a maximal treadmill test, while body fatness was calculated using a seven-site skinfold test and body mass index. Both a single and a combined analysis of how changes in fitness and fatness affect CVD risk factors were conducted; each variable was first analyzed independently (adjusting for the other variable) and then along with its counterpart to provide a more complete understanding.
At the end of the study, 752, 426 and 597 participants developed hypertension, metabolic syndrome and hypercholesterolemia, respectively. In the individual analysis, the researchers found that study subjects who maintained or improved their fitness level had a significantly lower risk of developing any of the three CVD risk factors compared to those whose fitness level decreased (with a 24% and 23% lower risk of hypertension, a 38% and 41% lower risk of metabolic syndrome, and a 25% and 26% lower risk of hypercholesterolemia, respectively). Conversely, the researchers found that those who gained body fat had a significantly higher risk of developing any of the CVD risk factors than those who lost fat, at 24%, 52% and 41%, respectively. The associations were found after accounting for possible confounders, lifestyle changes, and fitness and fatness for each other.
In the combined analysis, the researchers found that maintaining or improving fitness attenuated—although not completely eliminated—the increased risk caused by gaining fat. Similarly, reducing body fat appeared to counteract part of the increased risk associated with losing fitness. In addition, those who maintained their fitness and fatness did not have higher risks of developing CVD risk factors compared to those who gained fitness and lost fatness.
While previous studies have shown that low fitness and high body fatness are associated with CVD, several methodological differences distinguish the current study from the existing literature. Specifically, the ACLS’s independent analysis allowed fitness and fatness to be adjusted for each other, a factor that isn’t taken into account in many fitness/fatness studies. In addition, the ACLS measured fitness and fatness at more than one examination, allowing the research team to determine how changes in these variables across time affect CVD risk factors (many fitness/fatness studies use only one assessment at a single time point). The multiple measurements also allowed the ACLS to establish a possible causal relationship between changes in fitness/fatness and CVD risk factors. Since all participants were free of hypertension, metabolic syndrome and hypercholesterolemia at both the baseline and second examinations, these risk factors themselves could not have contributed to the change in fitness or fatness between the two examinations. Finally, the ACLS used objective measurements for fitness and fatness, whereas many studies used self-reported physical activity or body mass index.
Noting that the study “expands knowledge about the effects of fitness and fatness on CVD” by examining these factors both independently and in combination, the researchers added that the study findings have both clinical and public health significance. Specifically, the finding that improved fitness can reduce part of the CVD risk associated with increased fatness may help the two-thirds of the U.S. adult population who are overweight or obese.  
“These days, extensive attention has been given to obesity and weight loss. However, maintaining or improving fitness, primarily by engaging in regular physical activity, is also at least as important as weight loss for reducing cardiovascular disease in healthy adults,” said lead study author Duck-chul Lee, PhD, of the University of South Carolina’s Arnold School of Public Health.  “Although improving fitness and losing fatness is ideally the best combination, our study also shows that as long as individuals maintain their fitness and fatness levels, which is less challenging, they are not likely to be at high risk of developing CVD risk factors.”
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