First the good news: improvements in diet and lifestyle may be responsible for a decrease in heart disease in American women. The bad news is that increasing rates of obesity are having a negative impact on health and may minimize the benefits of any healthful changes. A recent study published in the New England Journal of Medicine reported that diet and lifestyle are influencing heart disease trends in women.

This latest report from the ongoing Nurses' Health Study involved over 85,000 women, ages 34 to 59 who were free of heart disease and cancer at the study's start in 1980. Over the next 14 years, they routinely submitted information regarding their lifestyle, diet, and any development of heart disease to investigators several times. During the course of the study, the women made some improvements in lifestyle behaviors - smoking decreased by 41% and diets became more heart healthy. At the same time heart disease rates decreased. Researchers concluded that smoking cessation and better eating habits were largely responsible. An increased use of postmenopausal hormone therapy may have contributed to the declining rates as well.

What dietary changes caused this positive effect? The participants reported eating less red meat and full-fat dairy products and more poultry, fish and low-fat dairy, resulting in lower saturated fat intake and increased omega-3 fatty acids, found in fish. Other dietary changes included consumption of more fiber and folate, found in whole grains, fruits and vegetables - all believed to provide protection against heart disease.

Making these healthful changes may benefit the heart, but they do not necessarily guard against weight gain. Over the course of the study, the percentage of women who reported being overweight rose from 37% to 51%. Average body mass index (BMI) went up as well, indicating an increase in body fat as compared to lean tissue. The study volunteers are not unique. Studies in the US consistently find that the number of Americans classified as overweight has been steadily on the rise. Currently, more than half of all American adults are overweight and therefore at greater risk for heart disease, diabetes, stroke, and certain cancers.

As a woman ages she loses muscle mass. This, combined with a slowing of metabolism, means her body requires fewer calories to fuel her through the day. If adjustments aren't made in diet or activity level, she will gain weight and increase her risk for heart disease. This process is not inevitable, though. Muscle mass can be maintained or even increased by physical activity. Adding small amounts of exercise throughout the day - taking the stairs, walking around the block - will make a difference. Physical activity, in combination with healthful eating, can keep body weight under control.

Over the past 30 years there has been a decline in deaths from heart disease. It is not known for certain whether it is because fewer people have heart disease or if better treatment options mean that people are more likely to recover from a heart attack or stroke. This study further supports the view that the decrease is at least partly due to lifestyle changes. It is also becoming clear that maintaining a healthy weight is a key component which many have yet to achieve.