Obesity could lead to cancer, study finds

Obesity could lead to cancer, study finds

Ailments like Type 2 diabetes, heart ailment and stroke weigh on an obese person's mind. Now a new study adds cancer to the list of big concerns.

The study, published in Lancet Oncology on November 25, finds that globally 3.6% of all cancer cases — or five lakh — each year are linked to high BMI (25 kg/m2 or higher).

Researchers led by Dr Melina Arnold from the International Agency for Research on Cancer (IARC) used data from a number of sources including the GLOBOCAN database of cancer incidence and mortality for 184 countries. Dr Arnold and colleagues created a model to estimate the fraction of cancers associated with excess bodyweight in countries and regions worldwide in 2012, and the proportion that could be attributed to increasing BMI since 1982.

In India, the study found that up to 1.6% of all new cancer cases in women in 2012 were attributed to high BMI. In men, the figure was lower at less than 1%. Compared to Europe and North America, the figures for India are low but with surging cases of both obesity and cancer in India the study findings are relevant. (Annually, five lakh Indians die of cancer, according to WHO; the Obesity Foundation of India estimates three crore Indians are fighting obesity.)

Oncologists were always aware of obesity as a risk factor for cancer, but the study by Lancet made it official. Dr Siddharth Sahni says his own clinical practice records from 2006 to 2014 show a similar trend. "Of the 792 breast cancer patients I operated upon, 61% were obese," says Sahni, senior consultant breast surgeon, Indraprastha Apollo hospital, Delhi. While he believes a high BMI ups the risk of cancer by 30-40%, he is also quick to point out that a healthy BMI is not a guarantee of cancer-free life as there are so many other risk factors associated with the disease.

Experts say there's a strong link between breast, uterus, colon, kidney and lower end of food pipe cancers and obesity.

BMI or basal metabolic index is a simple tool that helps determine the amount of excess body fat and its associated risks. It is calculated by dividing a person's weight in kilograms by the square of height in metres. A BMI from 18.5 to 25 is healthy, 25-30 indicates an overweight individual, 30-35 is obese and above 35 severely obese.

Sahni explains obese individuals are at higher risk of cancer as fat deposited inside the body actively produces harmful substances. Dr Meenu Walia adds that fat tissue produces excess estrogen which has been associated with risk of breast and endometrial cancers.

"Obese people also have higher levels of insulin-like growth factors in their blood which may promote growth of certain tumours. Fat cells produce a hormone called adipokines which can stimulate cell growth," says Walia, director medical oncology at Max hospital, Delhi.

The findings, both globally and in India, of the study by Lancet reveal that obesity-related cancer is a greater problem for women than men, largely due to endometrial (womb/uterus) and post-menopausal breast cancers. Globally, in men, excess weight was responsible for 1.9% or 1.36 lakh new cancers in 2012; in women it was 5.4% or 3.45 lakh new cases.

"There's a strong link between breast, uterus, colon, kidney and lower end of food pipe cancers and obesity," says Dr Rajendra Badwe, head of surgical oncology at Tata Memorial hospital. But, Badwe believes that if an obese person manages to lose weight and bring his/her BMI within the healthy range, they bring down risk of this disease.

"In fact, one analysis found that if every adult reduced his or her weight by roughly 1 kg, about 1 lakh new cases of cancer could be avoided every year," Walia says.