Obesity and Sedentary Lifestyles

It is well known that obesity and sedentary behavior coexist and that both are associated with cardiovascular disease (CVD) in women. Data from the Centers for Disease Control (CDC) show that in areas of the United States where rates of obesity are higher than 30% (Fig. 1), the prevalence of adults who report no leisure-time physical activity is also higher than 30% (Fig. 2). Likewise, the prevalence of obesity and physical inactivity predicts the presence of CVD death (Fig. 3). To highlight the association between the 3 conditions, one can nearly superimpose these 3 maps from the CDC.

Fig. 1 Obesity trends* among U.S. adults. Behavioral Risk Factor Surveillance System, 2010.

*Body mass index ≥30 or ∼30 lbs. overweight for 5′4″ person

Available from: http://www.cdc.gov/obesity/data

Fig. 2 County-level estimates of leisure-time physical inactivity among adults aged ≥20 years: United States, 2008. Available from: http://www.cdc.gov/obesity/data

Fig. 3 United States: heart disease death rates. Women, aged 35+, 2000–2006. Available from: http://www.cdc.gov/dhdsp/maps/national_maps/hd_women.htm

More recently, however, questions have been raised about whether obesity and physical activity are independently associated with CVD risk or if they simply are associated with risk through known risk factors: diabetes mellitus, hypertension, and hypercholesterolemia. If the latter is true, risk reduction with pharmaceutical interventions—in spite of cost, side effects, and incomplete efficacy—might spare providers the difficult task of encouraging weight loss and promoting increases in physical activity. If the former is true, however, weight loss and physical activity are crucial therapies for the prevention of CVD in women.

Obesity and Cardiovascular Disease Risk

There is abundant evidence that obesity increases the risk of elevated blood sugar, hypertension, and hypercholesterolemia. Similarly, there is ample evidence that weight loss mitigates those risk factors. Several recent studies, however, have explored the question of whether obesity increases the risk of CVD in the absence of other comorbid conditions. Most of the evidence supports obesity as an independent risk factor for CVD in men and women (Table I).^1–4 Even in the absence of metabolic abnormalities or comorbid conditions, individuals who are obese have higher rates of cardiovascular events over their lifetimes. One study suggests that the mechanism for this increased risk may be related to the presence, in obese individuals, of elevated inflammatory markers that are associated with CVD.³

TABLE I. Summary of Studies Included in Review

Data that did not fully support obesity as an independent CVD risk factor came from a large study of men and women for whom obesity's effect on CVD seemed to be associated solely with its effect on other metabolic abnormalities.⁵ Although this well-done analysis might call into question obesity's role in CVD, its follow-up duration (8–10 yr) was shorter than the follow-up of similar studies. Consequently, the results might simply indicate that the cardiovascular effects of obesity are incurred not in the short run, but over decades.

Physical Activity and Cardiovascular Disease Risk

Like the question of obesity, it is important to understand whether physical activity directly reduces CVD risk or if it does so only by lessening other risk factors. Four studies published in 2011 provide evidence that physical activity not only reduces long-known CVD risk factors but reduces CVD risk on its own (Table I).^6–9 One study even suggests that the risk reducing benefits of exercise might be more pronounced in women than in men.⁷ It is of interest that as little as 75 minutes a week of light physical activity could reduce cardiovascular risk by as much as 14%.

Evidence-Based Interventions and Clinical Implications

The evidence described here supports the importance of weight reduction and physical activity in the prevention of CVD in women and men alike. Physicians can and should assist patients in this effort by using evidence-based programs. Two large randomized-control trials provide guidance on strategies and programs that work. The first study is the Diabetes Prevention Program (DPP). Individuals who were determined by laboratory testing to be at risk for diabetes were randomized to receive metformin or an intensive lifestyle intervention that promoted calorie control and 150 min/wk of physical activity. Fifty percent of the intensive lifestyle-intervention group lost 7% of their body weight and reduced their risk of developing diabetes over 3 years by nearly 60%, which surpassed the findings in the metformin group.¹⁰ The 2nd study compared the effects on CVD risk factors of an intensive lifestyle-intervention program (similar to that of DPP) in diabetic patients to the effects of routine diabetes support and education in a control group. The lifestyle-intervention group, in comparison with the control group, had greater weight loss and significantly greater improvement in blood sugar, blood pressure, and lipids.¹¹ Evidently, these programs accomplished CVD risk reduction not only by preventing or reducing known risk factors, but by reducing weight and increasing activity levels.

Use of these evidence-based programs has become easier for practitioners in two ways: 1) DPP educational materials are free and easy to obtain online, and 2) there are newly implemented community-based DPP programs for at-risk individuals. The DPP program materials can be downloaded at http://www.bsc.gwu.edu/dpp/lifestyle/dpp_part.html and are available in English and Spanish. Moreover, YMCA centers around the country are offering the DPP in the community. Participating centers can be found at http://www.ymca.net/diabetes-prevention.

Conclusions

Weight loss and physical activity independently reduce CVD risk in women and are important tools for prevention and risk reduction for CVD in women. Clinicians can assist patients with lifestyle changes by using the tenets and materials of the Diabetes Prevention Program in their offices or by referring patients to community-based programs at area YMCAs.