US Chronic Disease
CONCLUSION AND FUTURE DIRECTIONS
Given that >55% of US adults do not engage in regular physical activity and >75% do not consume at least five fruits and vegetables a day (261), it is no surprise that chronic diseases are the most common cause of preventable death in the United States. The evidence is overwhelming that physical activity and diet can reduce the risk of developing numerous chronic diseases, including CAD, hypertension, diabetes, metabolic syndrome, and several forms of cancer, and in many cases in fact reverse existing disease. Furthermore, risk of several other chronic diseases may be ameliorated by physical activity and diet, including musculoskeletal diseases such as sarcopenia (352), osteoporosis (398), and arthritis (253), as well as stroke and congestive heart failure (238), chronic renal failure (66), Alzheimer’s disease (182), and erectile dysfunction (97). For instance, it has been reported that only 16% of American women aged 45–64 and <10% of women >65 yr of age report ever engaging in strengthening activities (345). As discussed, especially in the case of hypertension and metabolic syndrome, several studies have shown that physical activity favorably affects chronic disease, but relatively few trials have simultaneously examined both dietary modification and physical activity. Consequently, further studies using combined interventions that attempt to maximize benefits are warranted, as recommended by the ATP III guidelines (98). Additionally, the molecular mechanisms by which physical activity and diet protect against chronic disease are not completely understood, and future studies using translational paradigms should be utilized.Figure 5 summarizes various potential mechanisms by which physical activity and diet may ameliorate cardiovascular-associated chronic disease risk.
Fig. 5.
Hypothesized mechanisms by which physical activity and diet reduce the risk of coronary artery disease (CAD), hypertension, and diabetes.
Many of the studies discussed applied a whole-diet approach, and it cannot be determined whether the benefits noted are due to a higher intake of antioxidants, phytochemicals, minerals, and/or fiber, a lower intake of fat, and/or changes in the dietary fatty acid composition, in carbohydrate type, and/or protein source; however, most likely all of these factors contribute. For example, when one macronutrient is removed, another is added, and whether the benefit is due to the added nutrient, the removed nutrient, or a combination of both is unknown. However, the evidence suggests that numerous dietary changes contribute to the reduction in chronic disease risk, including elimination of refined carbohydrates and fatty foods, such as fast food and sugar-containing beverages, and substitution with a diet based largely on whole foods high in fiber and nutrient density. For example, processing whole grains increases caloric density by ∼10% and decreases fiber and protein by ∼80 and 30%, respectively (86).
A concerted effort to increase primary prevention of chronic disease through the translation of research data on the value of exercise and diet to the general public and legislation to urge implementation of primary prevention strategies as opposed to opportunistic care are essential (99). It is commonly argued that it is difficult to change the lifestyle of obese and sedentary people, but such pessimism may not be justified. For a successful public health approach to chronic disease prevention, we cannot rely on pharmaceuticals but must implement long-term, sustainable behaviors that encourage healthy lifestyles. It is possible to achieve primary prevention of chronic disease by means of a nonpharmacological intervention that can be implemented in a primary health care setting. Chronic disease not only impacts life expectancy but also may significantly blunt quality of life years (268). Additionally, recommendations have been questioned on the basis of their practicality. For example, the Institutes of Medicine recommendation for physical activity of 60 min/day has been questioned on the basis of its feasibility. It is known that 30 min provides important benefits; however, this may be inadequate for maximal health benefits. Similarly, diets recommending higher fruit and vegetable intakes (≥7) (13, 21,269) and lower fat consumption have been criticized as a result of the perceived inability of patients to adhere to more intensive guidelines. We feel it is essential to make recommendations that are effective and to strive to achieve them, knowing that even some modification, i.e., performing 30 min of activity per day and consuming five fruits and vegetables, will possess important health benefits. In addition, weight loss is a beneficial side effect of diet and exercise, and focus should be shifted to chronic disease reduction because many patients will experience modest weight loss (2–5%) and in the majority of cases still be classified as overweight or obese, yet will significantly reduce their chronic disease risk profile independent of significant weight loss.
Finally, as we look to the role of diet and physical activity in preventing chronic disease in the future, modifying the lifestyle of children is paramount to reducing chronic disease risk. Most children consume diets high in fat, especially saturated fat (189), refined sugar (194), including fast food (55, 111), soft drinks, and high-calorie fruit juices, and there are known interactions between diet and activity patterns (244) and between in utero and postnatal lifestyle influences and risk of future metabolic disease (397). Furthermore, children are performing less activity as computers, televisions, and video games become more commonplace, combined with elimination of school physical education programs (101, 197). Encouraging healthy diets and activity in our nation’s children is critical to winning the war against chronic disease.
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