Gaining weight can change the structure of the heart and its ability to pump blood. But losing weight can reverse that process, which is potentially lethal.

Overweight is defined as a body mass index (BMI) of 25 or more and obesity as a BMI of 30 or more.

“People who gain weight, even just 5 percent, are more likely to have thickening on the left side of the heart, which is a well-established indicator of heart failure,” said researcher Dr. Ian Neeland, Professor of Internal Medicine at the Southwestern Medical Center of the University of Texas, in Dallas.

Weight gain also puts an effort on the heart, causing it to pump harder, which makes the heart muscle thicker. “Thick hearts can’t counteract change, and they can eventually fail,” he said.

Preventing weight gain is an important way to protect heart health. “The heart is very dynamic, very plastic. Small changes over time make big differences,” Neeland said.

At the start of the study, more than 1,200 men and women with an average age of 44 years who had no heart disease or any other condition that put them at risk of heart disease underwent magnetic resonance imaging of the heart, and various measures of body fat. These tests were carried out again seven years later.

The researchers found that people who increased their weight even by just 5 percent were more likely to have thickening and enlargement in the left ventricle, which is the lower chamber of the heart, and that is an indicator of future heart failure.

In addition, study participants were more likely to have small reductions in the pumping capacity of the heart, Neeland said.

These changes in the structure and function of the heart persisted even after the researchers took into account other factors that can affect the heart, such as hypertension, diabetes, smoking and alcohol consumption.

But people who lost weight were more likely to have a reduction in heart muscle thickness, Neeland said.

Effects of metabolic syndrome on the heart

Metabolic syndrome is a group of disorders that occur at the same time and increase the risk of heart disease, stroke and type 2 diabetes. These disorders include weight gain, increased blood pressure, high blood sugar levels, excess of body fat around the waist and abnormal cholesterol or triglyceride levels.

 Metabolic syndrome is increasingly common, and up to a third of American adults have it. If you have metabolic syndrome or any of its components, radical changes in lifestyle can delay or even prevent the appearance of serious health problems.

 High cholesterol and high blood pressure can contribute to the accumulation of platelets in the arteries. These platelets narrow and harden the arteries, which can lead to a heart attack or stroke.

 Research has shown that as weight increases to overweight levels, the risks of the following conditions also increase: