| Chapter 2: | Background |
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Furthermore, epidemiological studies and clinical trials have shown that physical activity could lower blood pressure in overweight as well as in lean subjects (73). As for lipid profile, the influence of physical activity is still unclear (74). A study done in adults free of cardiovascular diseases showed that moderate to high physical activity lowered the risk of low HDL-cholesterol levels but did not have beneficial effect on triglyceride, LDL-cholesterol, and total cholesterol (75).
Alcohol Drinking, Smoking, and Psychosocial Stress. Some cross-sectional and prospective studies have reported that no alcohol consumption increased the risk for the metabolic syndrome relative to moderate drinking (76, 77). This protective effect of light to moderate alcohol drinking might act through its beneficial alterations in HDL cholesterol and insulin sensitivity (78, 79). As for blood pressure, it has been estimated that excess alcohol consumption is responsible for up to 10% of hypertension. The hypertensive effects of even small doses of alcohol have been documented (80, 81). Analysis of National Health and Nutrition Examination Survey III (NHANES III) data showed that current smoking was associated with higher risk of metabolic syndrome, independent of other risk factors (76). Previous studies have shown that smoking impairs insulin action and peripheral glucose uptake, alters the blood lipid profile, and raises blood pressure (82). As for the effect of stress on the metabolic syndrome, animal experiments have shown that stress was involvedin the pathophysiology of cardiovascular disease (83). Epidemiological studies also indicated that neuroendocrine stress axes were activated in the metabolic syndrome (84).
2.1.2.3 Diagnosis of the Metabolic Syndrome
Establishing diagnosis criteria for the syndrome is necessary to estimate and compare its prevalence among different populations.