Is obesity to be blamed for cancer risk?

by Dr. Naresh Somani, Head of Medical Oncology Department, HCG Cancer Centre, Jaipur

Gone are the days when looking chubby defined our status of belonging to a well-fed family. Obesity or being overweight in India, estimated to affect 30% of the country’s population, is now steadily progressing towards being hailed as the leading cause of next health crisis. Blame it on junk food, sedentary lifestyle and stress, people are gaining uncontrolled weight or witnessing fluctuating numbers of weight scale.
Being overweight or obese refers to having more fat than muscle and bone in the body. While it may not necessarily affect your activity level much, it can pose a threat of developing multiple non-communicable diseases like heart problems, diabetes, hypertension and even cancer. Not every obese person may be at risk of developing cancer, but it is now increasingly becoming a matter of concern for people at risk of developing cancers. 
Explaining the link between Obesity and Cancer
The link between obesity and cancer risk is much higher than the other risk factors. Excess weight in the body can lead to an increased risk of developing breast cancer in menopausal women or endometrial cancer due to high levels of fat around the waist. How and when you gain weight is also crucial. Gaining weight during childhood and teenage years may become a potential risk factor for some cancers that can happen later in life, say for instance, ovarian cancer prior to menopause.
Although the link is complex, there are certain possible explanations that suggest ways obesity increases the risk of developing some cancers.
•        Being overweight or obese can lead to chronic and low-level inflammation that can cause DNA damage and ultimately, cause cancer. Long term inflammation can lead to uncontrolled growth of cells, thus leading to cancer. For example, chronic gallbladder inflammation is a risk factor for gallbladder cancer, hepatitis and chronic colitis for liver cancer and gastroesophageal reflux induced by chronic local inflammation for oesophageal cancer. 
•        Excess amount of oestrogen produced by adipose or fat tissue is likely to increase risks of gyneac cancers like breast, endometrial, ovarian, and others.
•        High levels of insulin are common in obese and insulin-like growth factor-1 (IGF-1) or insulin resistance can lead to type 2 diabetes. These may trigger colon, kidney, prostate, and endometrial cancers.
•        Factors like excess body weight during birth, dynamic weight gain and loss, especially during adulthood are also linked to development of different types of cancers. 
Types of cancers linked to Obesity
Studies have revealed that being overweight can lead to the following types of cancer:
•        Breast cancer
•        Prostate cancer
•        Gallbladder cancer
•        Uterine cancer
•        Pancreatic cancer
•        Head and neck cancer
•        Thyroid cancer
•        Colorectal cancer
•        Oesophageal cancer
•        Multiple myeloma
•        Meningioma
How maintaining healthy weight can help?
In order to decrease the chances of cancer risk, it is essential to maintain healthy weight. Losing as good as 5-10% of the body weight can help in reducing the risk of developing cancer. For patients with lower weight gain during adulthood may have lower risks of developing kidney and colon cancers and breast, ovarian and endometrial cancers in case of women after menopause. Whether it is planned or unintentional weight loss, the risks of cancer can be decreased by maintaining healthy weight through reduced production of hormones like insulin, androgens and oestrogens.
To prevent obesity and lowering cancer risk, here are some tips:
•        Exercise for at least 150 minutes in a week
•        Eat healthy portions of meal consisting of non-starchy vegetables, whole grains, fruits and legumes and animal protein
•        Avoid processed and packaged foods, sugary drinks
•        Rest to keep fatigue at bay to avoid overeating and making unhealthy food choices
•        Stick to the daily calorie count suitable for you
•        Make small changes in your lifestyle habits like walking while you talk over the phone, eating pre-determined portion sizes, maintain a healthy sleep routine and manage comorbidities
•        Seek support from family, physicians, diet consultants and gym trainers to ensure healthy weight loss
•        Say no to crash diets or long hours of fasting
Obesity and Cancer Survival
Obesity may worsen the quality of life and overall health in patients diagnosed with breast, colorectal or prostate cancers.  It also increases the chances of cancer recurrence and progression. Patients with high BMI, particularly in men, have an increased risk of local recurrence of rectal cancer while chances of survival are reportedly better when women with breast cancer undergo considerable weight loss, in comparison to patients with normal weight. Obesity can also increase the risk of incontinence for prostate cancer survivors who have been treated with radical prostatectomy.
Being overweight does not necessarily indicate the risk of developing cancer but it is always advisable to maintain healthy weight and seek medical attention in case of any unexplained and persisting symptoms continue to keep you fatigued and unhealthy.