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Mar 15, 2011

The Effect of Obesity on Heart Function

Extra weight increases risk for abnormal heart function and other cardiovascular risk factors.

When it comes to the relationship between obesity and heart failure—it’s complicated. Obesity is intimately intertwined with multiple health conditions that underlie cardiovascular disease including high blood pressure, diabetes, and abnormal blood cholesterol. In addition, weight gain is a frequent consequence of heart-damaging lifestyle choices such as lack of exercise and a fat-laden diet.

For some time, scientists have suspected that excess fat tissue, especially around the waist, has a direct effect on heart structure and function, even in the absence of other heart disease risks. To pursue this theory, researchers evaluated 950 older individuals of varying weights for signs of left ventricular (LV) diastolic dysfunction. This condition is characterized by changes to the structure of the heart’s main pumping chamber (left ventricle), which prevent it from filling sufficiently between beats. Although LV diastolic dysfunction can often be symptomless, it reliably predicts future heart failure. (Heart failure occurs when the heart muscle weakens and/or stiffens to the extent that it can no longer meet the body’s needs for blood and oxygen.)

The study subjects were divided into three weight groups—normal, overweight, and obese—based on their body mass index (BMI), a mathematical formula that calculates body fat based on height and weight. In accordance with standard definitions, a BMI below 25 was considered normal weight; BMI of 25 to 29.9, overweight; and BMI 30 or above, obese.

Each subject underwent a noninvasive echocardiogram exam to measure the dimensions of the heart, muscle thickness, and filling capacity of the left ventricle. Upon analyzing the results, the researchers found that the overweight and obese participants were more prone to abnormal diastolic function than the normal weight individuals. Unsurprisingly, these individuals were also more likely to have other cardiovascular risks such as high blood pressure, diabetes, and a larger heart mass. However, when the researchers controlled for the effects of the other risks, the overweight and obese subject still had up to a 60% higher chance of having LV diastolic dysfunction. It also made a difference how much extra body fat the person carried. The risk of abnormal heart function went up 4% for each point increase in BMI measurement.

With this study, researchers are to add one more dot to the line between surplus poundage and cardiovascular disease. The understanding that excess fat tissue can directly damage the heart muscle even before symptoms are evident reinforces the case for weight control as a key step in preserving heart health. 

Questions for You to Consider

  • Can weight loss improve my health?

  • Even a relatively modest weight loss of 5 to 10% of your body weight can produce health benefits such as lower blood pressure, lower blood sugar, and improved cholesterol levels. In addition, weight loss has been shown to help people with asthma have fewer attacks and use less medicine, and improve the quality of sleep in people with obstructive sleep apnea.
  • What is the best way to lose weight?

  • Weight loss boils down to a simple formula: burn more energy each day than you take in from food. A deficit of 3500 calories will net one pound of fat loss. Therefore, if you cut down your food intake by just 100 calories a day, you can expect to lose 10 pounds by the end of the year.

  • What are my risks for heart failure?

  • Heart failure is a serious but all too common condition. It affects about 5.7 million people in the United States and causes 300,000 deaths each year. Heart failure is more prevalent in young men, African Americans, and people over age 65, particularly women. Hereditary factors and congenital heart defects can also raise your risk.

    Heart failure develops when the heart muscle is damaged or overworked. Some of the primary contributors to heart failure include:
    • Obesity
    • Coronary artery disease
    • Heart attack
    • High blood pressure
    • Diabetes
    • Alcohol


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