Keep an eye on your BMI

Dr Shabber Zaveri

Obesity has become one of the most pressing health challenges of modern times, and its connection with breast cancer, especially in postmenopausal women, is both significant and alarming. While several factors contribute to breast cancer, excess body weight has emerged as one of the most preventable risk factors.

Understanding the risk

Multiple studies have shown that postmenopausal women who are obese face a 26 per cent higher risk of developing breast cancer compared to those with a healthy body weight. The relative risk ratio, according to pooled analyses, ranges from 1.08 to 1.41, and the longer a person remains obese, the higher their chances of developing breast cancer.

In contrast, premenopausal women may have a neutral or slightly lower risk associated with obesity, though the evidence is still evolving. The negative impact of obesity becomes more evident after menopause, particularly in women whose breast cancers are hormone receptor-positive (ER/PR-positive), meaning the tumour grows in response to estrogen and progesterone.

Obesity doesn’t just raise the risk of developing breast cancer; it also worsens survival outcomes. Research shows that obesity can increase the likelihood of recurrence and mortality by 35–40 per cent, especially in hormone receptor-positive cases.

Why does obesity raise the risk?

The connection between obesity and breast cancer is mediated by several biological pathways:

Chronic inflammation

In obesity, adipose tissue becomes hypertrophied and dysfunctional, which can lead to chronic, low-grade inflammation. This initiates the release of inflammatory mediators known as cytokines that can damage DNA, stimulate the development of new blood vessels for tumors, and enable cancer cells to evade the immune system.

Hormonal changes

With menopause, the ovaries stop producing estrogen, and body fat becomes the primary source of estrogen. Thus, greater body fat means higher circulating levels of estrogen, which is the fuel for hormone receptor-positive breast cancer.

Insulin and metabolic issues

Obesity is often associated with insulin resistance and hyperinsulinemia, which drives elevated levels of insulin-like growth factors (IGF). These factors stimulate cell proliferation and have the potential to promote breast cancer development.

Difficulties in early detection 

In the context of obesity, it can be very difficult to diagnose breast cancer early. In obese women, the breast lump can be hidden in the breast fatty tissue resulting in a delay in diagnosis, meaning that many obese postmenopausal women will be diagnosed at stage 3 or 4 when the breast cancer has metastasized to the bones, lungs, or brain.

Importance of screening 

Early detection is critical for survival. Unfortunately, India’s screening rates remain low, and the majority of women, even in urban settings, delay screening due to fear and misconceptions about breast cancer, such as the belief that “breast cancer always hurts.” In fact, 99 out of 100 breast cancers do not hurt early on.

According to current guidelines, all women over the age of 40 should have yearly breast screening which consists of a mammogram and a breast ultrasound. Women who cannot lose weight because of other medical conditions such as arthritis or heart disease should still have yearly breast imaging to detect cancer early.

Steps for prevention 

While not every risk factor is something we can change—whether it is age, heredity, or another health issue—obesity is modifiable. Here are some practical steps to lower risk: 

•Maintain a healthy weight: Keep your Body Mass Index (BMI) under 25.
•Get regular exercise: Aim to add at least 180 minutes of exercise per week with activities such as brisk walking, cycling, or swimming. This activity burns calories and improves hormone regulation.
•Eat wisely: Concentrate on a balanced diet which consists of fruits, vegetables, whole grains, and lean proteins. Refrain from sugar, processed foods, and saturated fats.
•Limit alcohol and stop smoking: Both are carcinogens and increase risk.
•Consider bariatric surgery: If you are severely obese and unable to lose weight using traditional means, weight loss surgery can significantly lower your long-term risk.

(The author is chairman, HOD and consultant - surgical oncology & robotic surgery at a Bengaluru hospital.)