“In India lifestyle diseases like diabetes, obesity and hypertension are quite common and there is definitely a biological plausibility between these diseases and cancer. Because, when a person has diabetes, they definitely have insulin resistance and are generally obese, both factors that put a person at risk of suffering from cancer.” Says Dr Ashay Karpe, Medical Oncologist and haematologist, Sunrise Oncology Centre.
Type 2 diabetes increases your risk of suffering from several cancers: Colon cancer , Breast cancer in postmenopausal women , pancreatic cancer , liver cancer , endometrial cancer , bladder cancer  and Non-Hodgkins lymphoma 
How does it work?
While most cancers develop over about 10 to 20 years, there are several factors, including obesity, diet, type 2 diabetes, dietary choices and physical activity that inhibit or promote cancer development. [9–11]
Here are the three factors that link diabetes and cancer. 
Hyperinsulinemia (increased production of insulin)
Cancer cells feed off sugar and metabolise glucose at 200 times the regular rate. Known as the Warburg effect, cancer cell’s affinity for sugar is what makes hyperinsulinemia perfect for cancer cells grow and proliferate.
Increased insulin levels also cause damage to cell at the level of the DNA, leading to mutations and then cancer.
Increased hormone production in women
In postmenopausal women, body fat is the primary site for estrogen synthesis. The higher the fat, the higher the risk of suffering from postmenopausal breast and endometrial cancer.
Increased insulin has a role to play here as well — it is known to increase bioavailable estrogen and testosterone, which raises the risk of cancer.
Type 2 diabetes and obesity have one thing in common: Chronic, low-grade inflammation. This inflammation increases the production of free radicals that damage DNA and lead to cellular mutations leading to cancer. [12, 13]
Also, adipose (fat) cells produce several chemicals which increase inflammation ( interleukin-6 or IL-6, tumour necrosis factor-α (TNF-α)) that, some studies have found, increase the risk of colorectal, breast, prostate, lung cancer, and other cancers.[14,15]
Higher body fat, coupled with insulin resistance (in diabetes) increases production of a chemical called leptin, also linked to colorectal, postmenopausal breast, and potentially other cancers. 
How does diabetes affect the treatment of cancer?
Dr Ashay Karpe says, “People with diabetes, often can have cardiac problems, kidney-related problems and in some cases even brain-related problems. So, diabetes directly or indirectly puts a restriction on the types of treatments a person with cancer can undergo. Therefore as physicians, we need to have a very clear control of a patient’s diabetes while giving them treatment for cancer.
Therefore in the case of people with diabetes and cancer, the intensity of the treatment has to be altered. They are also at a higher risk for infections.”
Can cancer be prevented, if you have diabetes?
Dr Ashay Karpe says, “When people want to reduce the risk of developing cancer, they should definitely focus on losing weight. They should follow a diet regimen which will help them reduce insulin resistance and lower their weight. They should consult the physician who is managing their diabetes and keep strict control of their sugars.”
Apart from losing weight, and managing your sugar levels well, you should also focus on eating a plant-based, balanced diet that is rich in vegetables, whole grains and fruits.
Regular exercise is also another pillar of effective weight loss, and increasing muscle mass, that helps burn fat and regulate sugar levels in your body.
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