A National Cancer Institute study showed that exercise cuts a woman’s risk of breast cancer. However, it must be vigorous exercise. Also, this only showed results in women who were not overweight. A possible explanation for the weight problem is that overweight and obese women found moderate exercises more taxing than non-overweight women and misreported it as vigorous exercise.
The study analyzed data collected from over 32,000 postmenopausal women over 11 years as part of the Breast Cancer Detection Demonstration Project
Participants were asked about their exercise habits and their activities were subsequently rated as either moderate or vigorous.
Moderate, or “non-vigorous” activities include:
- Light housework such as vacuuming of washing clothes
- Home repairs such as painting
- Mowing the lawn
- Light sports of exercise
- Walking, hiking, or light jogging
No association was found between non-vigorous activity and breast cancer.
Activities rated as "vigorous" include:
- Heavier housework such as scrubbing floors or washing windows
- Digging in the garden or chopping wood
- Strenuous sports or exercise
- Running, fast jogging, or aerobics
The decrease in breast cancer seen in women with a lot of vigorous exercise was small, but had a more pronounced effect in women who were not obese or overweight. The risk of breast cancer decreased by about 30% when women of normal weight who exercised vigorously were compared to women who did no vigorous activity at all.
