Obese people have twice the chance of developing coronary heart disease than those who have a lower body mass index. According to James R. Sowers, writing in “Clinical Chemistry,” obesity affects the heart through its influence on risk factors such as insulin resistance, hypertension, atherogenic dyslipidemia, a prothrombotic state of the blood, and systemic inflammation. This cluster of health problems is known as the metabolic syndrome, of which abdominal obesity is the most prevalent manifestation.
Insulin Resistance
A direct relationship exists between excess abdominal fat and the development of insulin resistance, the inability of the body to respond to normal insulin levels. Type 2 diabetes develops when either the body does not produce enough insulin in the blood or cells fail to recognize the insulin produced. According to the American Heart Association, insulin resistance is a strong indicator of metabolic disorders and is associated with the development of atherosclerosis and plaque buildup in coronary artery walls.
Hypertension
Being obese increases the risk of developing high blood pressure, or hypertension, and hypertension greatly increases the risk of coronary artery disease. The American Heart Association reports that risk estimates from population studies suggest that more than 75 percent of hypertension can be directly attributed to obesity. When blood pressure is too high, coronary artery walls become weakened and more susceptible to the plaque buildup of atherosclerosis. It is then more difficult for the heart to pump blood through the clogged arteries, increasing the risk of a heart attack.
Dyslipidemia
Obesity has a negative effect on lipid--fat--levels in the blood, which often leads to the development of a condition known as dyslipidemia, a blood fat disorder characterized by high triglycerides, low HDL, or "good" cholesterol, and high LDL, or "bad" cholesterol. This combination of factors produces ideal conditions for developing coronary artery disease as the result of plaque buildup in artery walls. This abnormal shift in lipid levels in the blood is directly linked to weight gain.
The Prothrombotic State
Thrombosis is the formation of a blood clot, or thrombus, inside a blood vessel which obstructs blood flow through the vessel. One of the components of the metabolic syndrome is a prothrombotic state in which there are high levels of fibrinogen or plasminogen activator inhibitor-1 in the blood. Scott M. Grundy, writing in “Circulation,” explains that fibrinogen is a protein that promotes clot formation; thus elevated levels increase the risk of a heart attack. Plasminogen activator inhibitor-1 inhibits fibrinolysis, the process that dissolves blood clots; therefore high levels increase the risk of clot formation.
The Proinflammatory State
Adipose tissue is an active endocrine organ that secretes certain cell-too-cell signaling proteins. Studies by Satoshi Nishimura, reported in “Discovery Medicine,” show that when in obesity adipose tissue shifts to producing inflammatory immune system signaling proteins, this change fosters the low-level systemic inflammation characteristic of chronic diseases such as atherosclerosis that are associated with the metabolic syndrome. Elevated C-reactive protein in the blood, a marker for inflammation and a risk factor for atherosclerosis, is also seen in the inflammatory state of the metabolic syndrome.
References
- “Clinical Chemistry”; Obesity and Cardiovascular Disease; James R. Sowers; 1998
- “Circulation”; Diagnosis and Management of the Metabolic Syndrome; Scott M. Grundy; 2005
- “American Heart Association”; Obesity: Impact on Cardiovascular Disease; Ronald M. Krauss; 1998
- “Discovery Medicine”; Adipose Tissue Inflammation in Obesity; Satoshi Nishimura; 2009
