Overweight women who exercise mitigate their heart risk

Summarized by Susan Aldridge, PhD, medical journalist
May 9, 2008

Summary

A new report from the Women's Health Study dissects out the different impacts of weight and level of physical activity upon heart disease risk. The combination of healthy weight and regular exercise scored best. However, women who were overweight or even obese had a reduced heart disease risk if they were physically active.

Introduction

Both physical inactivity and obesity are modifiable risk factors that influence the risk of heart disease. Some studies have suggested that your level of physical activity is the most important factor. Others say that body mass index (BMI) is more significant. Researchers at Brigham and Women's Hospital, and elsewhere, used data from the long-running Women's Health Study to try to assess how exercise and BMI affect heart disease risk.

What was done

The Women's Health Study was set up to find out whether low-dose aspirin and vitamin E can prevent heart disease and cancer. It involves a group of nearly 40,000 female health professionals aged 45 or more who were healthy at the start of the study in 1992. They are a rich source of data for researchers studying risk factors and heart disease. Their BMI was recorded and they were also asked about the time they spent each week in physical exercise of various kinds. The researchers then followed them up each year, for around 11 years, and recorded any incidences of heart disease, such as occurrence of heart attack or needing a procedure like cardiac bypass.

What was found

There were 948 cases of heart disease occurring during the follow up period. At the start, 34 percent of the participants were classed as being physically active, expending 578 kcal per week. When it came to BMI, 51 percent were normal weight, 31 percent overweight and 18 percent obese. Elevated BMI was linked to high blood pressure, diabetes, and high cholesterol and these women were less likely to be physically active.

The risk of heart disease went up with BMI with obese women being more at risk than overweight women. Physical activity was also a factor with the most active women being less likely to develop heart disease. This means that overweight or obese women who were physically active were less likely to have heart problems than those who were inactive. Two different things are happening, the researchers explain. Fat cells may release substances that harden the arteries and cause inflammation, both setting the scene for heart disease. Exercise improves blood vessel functioning and decreases the risk of blood clotting, which will improve heart health. The study therefore shows that exercise can lower, but not eliminate, the risks of being overweight or obese.

What this study means

This new research shows, as in previous studies, the importance of both exercise and weight in the risk of heart disease. It sheds new light on the interrelationship between the two. For physical activity can reduce the risk posed by excess weight. The researchers say their work backs current advice to take 30 minutes of moderate exercise per day. This is a minimum to aim for, because they learned that more exercise reduced the risk of heart disease further. But keeping to a healthy weight seems to be even more important because no amount of exercise can eliminate the risk of being overweight or obese. Therefore, women of all weights can benefit from exercise. But they can gain even more if they shed any excess pounds.

Source

• The Joint Effects of Physical Activity and Body Mass Index on Coronary Heart Disease Risk in Women AR. Weinstein, HD. Sesso,  et al., , April 28, 2008, vol. 168, pp. 884--890

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