First of all we should clarify who can be considered overweight and who is obese. The main tool to check it is Body Mass Index (BMI) – see in following page. Generally speaking, the BMI over 25 should be considered as overweight and/or obesity.
Several studies mentioned correlation between obesity and increased risks for breast cancer (especially for postmenopausal women). Researchers mentioned that increased risks for postmenopausal women were noted in women with BMI equal to 35 and/or higher.
Obesity during postmenopausal period increases the breast cancer risks up to 30-60% (comparing with thin postmenopausal women). Scientists highlight that it is more important for women with hormone-sensitive types of breast cancer (for tumors that express both estrogen and progesterone receptors). At the same time, overweight and obesity cannot be risk factors for other types of breast cancer (tumors with negative hormone receptors).
Strange news is that few studies demonstrated reduced risks for breast cancer in obese premenopausal women – being overweight before menopause modestly decreases breast cancer risks (by 20-40%). Does it mean that women for breast cancer prevention should be fat before menopause and thin after menopause?
Some epidemiological studies show that step by step weight gain during women life from 20 to 50-60 can be considered as an increased risk for postmenopausal breast cancer. Why? Because before menopause women ovaries are producing most estrogens of the body; after menopause, the “old, retired” ovaries no longer produce much estrogen and estrogens mainly come from fat tissue. Fat tissue contains an enzyme called aromatase that converts hormones called androgens (made mostly in the adrenal glands) to estrogens. There is a correlation between BMI and levels of estrogens – higher BMI trigger increased levels of hormones.
Point is that after menopause, when the ovaries stop producing sex hormones, fat tissue becomes the most important source of estrogens. Increased levels of estrogen in obese postmenopausal women can trigger hormone-sensitive breast cancer. Losing weight after menopause could help decrease risks of breast cancer development.
Obesity and Breast cancer
Link between obesity and breast cancer is still not clear and can be affected by several factors such as used hormonal medications, genetic factors, age, location of fat tissue, etc.
“We can’t change our genes or family history, but we can change our lifestyle habits and aim to maintain a healthy weight to lower breast cancer risk,” said lead researcher Marian Neuhouser, a professor of epidemiology at the Fred Hutchinson Cancer Research Center in Seattle.
Being overweight also can increase the risk of the breast cancer recurrence in women who have had the disease. Maintaining a healthy weight is important for breast cancer survivors.
For breast cancer survivors, being overweight increases the risk for cancer recurrence and mortality (death from breast cancer). According to medical experts, women who lost weight during the study reduced their risk for breast cancer.
