A series of studies have shown that being obese or even overweight may boost a person’s risk of developing up to a dozen different types of cancers. It is already known that obesity is a major issue worldwide and raises the risk of diseases such as type 2 diabetes and heart disease. According to the World Health Organization, there are 400 million people classified as obese and 7.6 million people died last year, worldwide, because of cancer.

Now, researchers at the Women Veterans' Comprehensive Health Center at the San Francisco Veterans Affairs Medical Center led by Dr. Karla Kerlikowske associate obesity in women with an increased risk of breast cancer. Such an assumption is not new, especially in postmenopausal women who follow hormone replacement therapy, known to increase breast cancer risk.

However, this time, the researchers identified an increased breast cancer risk in women who did not follow such therapy. The study is to appear in the Dec. 3 issue of the Journal of the National Cancer Institute.

The researchers collected ongoing data from mammograms performed on more than 287,000 women past menopause. The study found that “the risk of an advanced stage cancer for an obese woman is 56 percent to 82 percent higher than for a normal-weight woman,” Dr. Kerlikowske said. In fact, the more obese a woman was, the higher her risk for breast cancer.

Previously, the researchers blamed the increased breast cancer risk in obese women on the fact that these women do not have regular mammograms or cancer in their case might be easily missed because of fat. But this study does not make such an analogy. In fact, the researchers said that heavy women have an increased level of estrogen, which appears to fuel tumors leading to “estrogen receptor-positive” cancers.

The study is a wake-up call for heavy women who are often encouraged to lose weight in order to avoid deadly diseases. In fact, this is the only factor a woman can change to decrease her risk of breast cancer, scientists say. Other factors such as family history of breast cancer or genetic mutations cannot be changed.