Exercise and Nutrition Still Impacts the Metabolic Syndrome: A Clinical Perspective

August 2, 2016
Kenneth Johnson, MD, MBA, FACC

When examining the components that contribute to the metabolic syndrome, lifestyle modification involving disciplined dietary control and increased physical activity can become more critical than medical therapy.

What is the metabolic syndrome?

The metabolic syndrome describes a well-defined aggregation of factors that together increase an individual’s risk for the development or propagation of atherosclerotic cardiovascular disease and type 2 diabetes mellitus. The components of the syndrome have been well described in the literature for years.

The constellation of factors has been previously identified by many names including syndrome x, the insulin resistance syndrome, the dysmetabolic syndrome, and the obesity syndrome. The American Heart Association and National Heart, Lung, and Blood Institute have both defined the metabolic syndrome as the presence of 3 of 5 of the following characteristics: increased waist circumference, elevated triglycerides, reduced high density lipoprotein (HDL-C), elevated blood pressure, and elevated blood glucose (see table 1). Individuals meeting criteria for the metabolic syndrome represent a high risk population for future cardiovascular events and require aggressive treatment to reduce this risk.

Table 1: AHA/NHLBI diagnostic criteria for metabolic syndrome

Risk Modification

Although this syndrome is marked by the aggregation of these risk factors, it has no uniform pathogenesis. However, it is well established that the metabolic syndrome is most likely to occur in individuals who have two predominant underlying risk factors: insulin resistance and abdominal obesity. Given this, it should not be surprising to realize that other conditions that increase risk for the syndrome include physical inactivity, advancing age, and a high carbohydrate diet. Moreover, a diet high in saturated fat and cholesterol worsens insulin resistance and increases the atherosclerotic risk in those with the metabolic syndrome.

The cornerstones of managing cardiovascular risk in individuals with or without the metabolic syndrome hinges on aggressive risk factor modification. Primary prevention strategies for individuals who are diagnosed with the metabolic syndrome include lowering LDL cholesterol, controlling hypertension and intensely managing diabetes. In addition to drug therapy, individuals with these risks most often require a foundation of lifestyle changes.

Confronting the Western Diet

It is undeniable that high carbohydrate diets and increased saturated fat intake are associated with the metabolic syndrome.  Commonly, diets with these two features are considered “Westernized,” as they are more pervasive in countries such as the United States.  Studies that examine similar ethnic populations with different dietary patterns show that a Western diet is linked more prominently to the risk of developing the metabolic syndrome.

On the contrary, diets that incorporate fish, dairy, cereal grains, plant-based foods and healthy oils (such as olive oil) decrease the risk of developing the syndrome, and have been shown to correct the metabolic abnormalities in individuals who previously have met the diagnostic criteria for the disease. Dietary modifications noted above seem to not only combat the insulin resistance component of the metabolic syndrome, but address the abdominal obesity aspect as well.

Studies have identified that insulin sensitivity can be affected by dietary composition, and specifically, diets high in saturated fat have been found to increase insulin resistance.  Similarly, Western diets contribute to the characteristic “central” or abdominal obesity that is the most common trait of this syndrome.  Studies conclude that both reduced carbohydrate and low-fat diets can improve insulin resistance as well as abdominal fat distribution.

Given these compelling data, the American Heart Association recommends that in patients with the metabolic syndrome, an atherogenic diet consisting of increased saturated fat, trans fat, and cholesterol should be modified to reduce saturated fat to < 7% of total calories; reduce trans fat; decrease dietary cholesterol to < 200 mg/dL; maintain total fat to 25% to 35% of total calories; assure most dietary fat is unsaturated; and limit intake of simple sugars.

Cardiorespiratory Exercise

Although poor nutrition can place individuals at jeopardy for developing the metabolic syndrome, lack of physical activity is equally as dangerous a culprit in the process. Research suggests low energy expenditure in conjunction with sedentary activities can promote maladaptive physiological responses that ultimate contribute to developing the metabolic syndrome.

Furthermore, low levels of cardiorespiratory fitness measured by respiratory gas exchange analysis have been shown to increase risk of developing the metabolic syndrome. Increased exercise, on the other hand, has been shown in one pivotal epidemiological study to be associated with a reduced prevalence of the metabolic syndrome.

Additionally, in the same series, those who adopted a Mediterranean diet in conjunction with light to moderate physical activity were less likely to have the metabolic syndrome compared to those who were conforming to exercise or diet alone.

Patients with the constellation of risks that define the metabolic syndrome remain a clinical challenge, particularly in countries such as the United States where a Western diet predominates and obesity has reached epidemic levels. Globally, risk factor modification for cardiovascular disease requires a solid foundation of lifestyle modification that largely relies on a “non-Western” diet and exercise.

In the case of the metabolic syndrome, compelling data further supports the utility of diet and physical activity, but, even more, these simple lifestyle changes can produce a dramatic impact on and even abolish the syndrome completely.

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