Breast cancer and Obesity

While there are various parameters to define overweight such as abdominal obesity, BMI and body weight, an increase in body fat is related to a greater risk of postmenopausal breast cancer.

Breast cancer and Obesity
PINK stands for HOPE and STRENGTH. Breast Cancer Awareness Month.

We are in an era where as a society we are keen to embrace everyone from every walk of life. As a society, we are relegating race/gender/ ethnicities/body types to the confines of history. An individual’s right to choose for him/herself is respected by one and all. In this prevailing socio-cultural environment, how do I speak about weight without being labelled as someone who is body shaming? But it needs to be told! The scientific and anecdotal evidence are overwhelmingly pointing in a single direction - obesity harms.

And when it comes to a serious, debilitating illness such as cancer, it has to be told.

What does medical science tell us about overweight and obesity?

The standard definitions of overweight and obesity is based on BMI (Body Mass Index) calculated from weight and height.

As per information published by WHO in June 2021

  • Worldwide obesity has nearly tripled since 1975.
  • In 2016, more than 1.9 billion adults, 18 years and older, were overweight. Of these over 650 million were obese.

WHO further elaborates thus -

https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
https://www.cancer.gov/about-cancer/causes-prevention/risk/obesity/obesity-fact-sheet

The data and statistics are alarming! It's equally distressing to note that obesity, which is one of the easily manageable causative factors in cancers, is not sufficiently addressed.

Out of the list above, one that stares back at us is Breast Cancer.

WHO does not mince any words while elaborating the problem statement on breast cancer :

https://www.who.int/news-room/fact-sheets/detail/breast-cancer

The following are the most common risk factors of breast cancer:

  • Female gender (the greatest risk for breast cancer)
  • Increasing age
  • Obesity
  • Excessive consumption of alcohol
  • Family history of breast cancer
  • History of radiation exposure
  • Reproductive history (such as age that menstrual periods began and age at first pregnancy)
  • postmenopausal hormone therapy
  • Certain inherited “high penetrance” gene mutations greatly increase breast cancer risk, the most dominant being mutations in the genes BRCA1, BRCA2 and PALB-2.
https://www.nhp.gov.in/breast-cancer-awareness-month_pg

Weight control and managing obesity remains one of the foremost modifiable risk factors in prevention of breast cancer, especially post menopausal breast cancers. Obesity also alters the health and treatment outcomes in breast cancers, having a negative impact on prognosis of both Pre & Post menopausal women.

https://news.cancerresearchuk.org/2015/11/25/how-exactly-does-obesity-cause-cancer/

The possible mechanisms that have been suggested to explain the relationship between obesity and cancer are:

Inflammation

Obesity leads to chronic low level inflammation at cellular level. This micro inflammation increases the survival and growth of cancer cells.

Sex hormone imbalance, the estrogen factor.

Fat tissue (adipose tissue) becomes the main organ producing estrogen in the post menopausal women.This is carried out by the enzyme called aromatase in the fat tissue.This is significant in hormone dependent tumours of the breast, commonly reported as ER + tumours.Thus obesity is directly linked to the increased levels of estrogen.

Insulin

Insulin stimulates aromatase activity in fat tissue increasing esotrogen production. Obesity also causes insulin resistance (hyperinsulinemia). Hence obese people have increased levels of blood insulin and IGF-1 (Insulin like growth factor-1). Hyperinsulinemia and high IGF-1 levels stimulate breast tumours. Similarly high blood glucose levels seem to increase the risk of breast cancer.

Adipokines

Fat cells produce certain hormones, called adipokines, that may stimulate or prevent cell growth. A type of adipokine called leptin promotes cell growth and may be a causative factor in tumour growth. Leptin levels increase in blood with increasing body fats. Likewise adiponectin, an adipokine,inhibits breast tumour formation. Levels of adiponectin are reduced in obese individuals. To summarise, obesity increases breast tumour activity.

Other factors:

  • Obesity also increases the oxidative stress on our body, thus contributing to the ongoing process of micro inflammation.
  • Immune responses are altered in obesity.

The paradox of the benefits of Obesity in Cancer

The old and new data have shown that moderately increased BMI improves the survival and response to therapy. However, this effect is lost when BMI increases to morbid obesity levels, leading to the concept of “obesity paradox”

While we own our bodies and are confident about being “us”, we owe it to ourselves to own our health too. And maintaining a healthy weight and reducing body fat is a responsible action which will ensure longevity and improved quality of our lives.

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