A new Lancet study has found that diabetes and high BMI (above 25 kg/m2) were the cause of 5.6 per cent of the new cancer cases in 2012. The study analysed 7,92,600 cases reported from 175 countries around the world. Published in The Lancet Diabetes and Endocrinology, the study found that of the new cases in 18 kinds of cancer, 5,44,300 were attributable to high BMI, equivalent to 3.9 per cent of all cancers — nearly double that of the 2,80,100 cases attributable to diabetes (2 per cent).
Calculated on the basis of an individual’s height and weight, BMI or body mass index (a person’s weight in kg divided by the square of height in metres) is recognised the world over as a measure of obesity.
The study estimated that nearly a quarter (24.5%) of the 7.66 lakh new cases of liver cancer, and 38.4% per cent of the 3.17 lakh new cases of endometrial cancer were attributable to high BMI and diabetes. 26.1 per cent of the new diabetes-related cancers (7.7 lakh cases) and 31.9 per cent of the new BMI-related cancers (1.74 lakh cases) were attributable to increase in the prevalence of these risk factors from 1980 to 2002, added the study.
The findings are important for India as, with an estimated 62 million diabetics, it is widely considered the diabetes capital of the world.
According to a 2014 article in the Australian Medical Journal, “…prevalence of diabetes is predicted to double globally from 171 million in 2000 to 366 million in 2030, with a maximum increase in India. It is predicted that by 2030, diabetes mellitus may afflict up to 79.4 million individuals in India.”
Additionally, for India, the BMI obesity cut-off has been lowered from the global 25 kg/m2 to 22 kg/m2, given the proneness of Indians to truncal obesity, that increases the risk of various ailments.
According to data collected by the Central Bureau of Health Intelligence, India had 10,57,204 cases of cancer in 2012. The National Cancer Registry recorded around 14.5 lakh cancer cases in 2016-17 in the country.
Dr P K Julka, former dean and professor of oncology at AIIMS, said, “Obesity is known to be a major risk factor for several cancers, including that of the breast. In the fat tissue, male hormones are converted to female hormones with the help of an enzyme called aromatase. Female hormones are known to be responsible for breast cancer. Obese people are also more prone to cancers of the uterus and gall bladder. The risks for diabetics also stem from obesity because they are generally obese people with sedentary lifestyles. Most cancers are actually preventable because they have lifestyle causes.”
However, he said there were no Indian studies examining whether the low BMI cut-off for Indians, applied for cardiovascular risks, is also true for cancer risk.
Global estimates suggest that 422 million adults have diabetes and 2.01 billion adults are overweight or obese. High BMI and diabetes are risk factors for various types of cancer possibly because of the adverse effects on the body of high insulin, high sugar levels, chronic inflammation, and dysregulated sex hormones such as oestrogen, all of which are associated with these diseases.
For the Lancet study, researchers from Imperial College, London, University of Kent and International Agency for Research on Cancer assessed the increase in new cases of 18 cancers in 175 countries between 1980 and 2002, based on the prevalence of diabetes and high BMI.
“As the prevalence of these cancer risk factors increases, clinical and public health efforts should focus on identifying preventive and screening measures for populations and for individual patients. It is important that effective food policies are implemented,” said Dr Jonathan Pearson-Stuttard of Imperial College London, lead author of the Lancet study.
The proportion of cancers related to diabetes and high BMI is expected to increase globally as the prevalence of the two risk factors increases. Using projected prevalence of diabetes and high BMI for 2025 compared with the prevalence in 2002, the researchers estimate that the proportion of related cancers will grow by more than 30 per cent in women and 20 per cent in men on an average.