Obesity and related Cancer

Dr. A K Nanda      

MD, Radiation Oncology

Need for Oncogyan (knowledge about Cancer)

        In oncology OPD, every day oncologists have to reveal the diagnosis to the patients and relatives. Being diagnosed with cancer is perhaps the worst news in their life. Hence all oncology students learn the art of “breaking bad news” in their study period. But why it is the worst news? Perhaps because who ever is diagnosed with cancer is going to die. One should keep in mind that mortality in cancer is high because most of the cases are diagnosed in advanced stage. Hence knowledge about cancer is necessary now a days, first to keep yourself away from the causative factors of cancer and second for early diagnosis. Smoking is the major causative factor which is known to every one. But there are other causative factors which may increase chance of cancer occurrence, which are unknown to many. That’s why, it is the need of the hour to discuss such things.
{For relation of cancer with passive smoking 'click here' and with alcohol 'click here'.}

Obesity:

• Obesity is the disproportionate body weight for height.
• When a person is overweight or obese, it means that they have too much body fat in relation to lean body tissue, such as muscle.
• People who are overweight have a higher risk of many serious health conditions, including type-2 diabetes, high blood pressure, and heart disease.
• Being overweight is also associated with an increased risk of many types of cancer.
• At a global level, excess body weight is the third commonest attributable risk factor for cancer (after smoking and infection).
• But in western populations such as the UK, excess weight ranks as second commonest risk factor.
• In Australia, overweight and obesity are the 4th major cause of cancer following smoking, solar radiation and inadequate diet.
• For India we will be discussing below that, the cut off BMI is less than the average BMI of world population. Though there is less data regarding obesity and cancer in India, there must be a significant relationship between these two.

Facts about obesity and cancer

• Worldwide, one-fifth of the adult are obese.
• 20% of new cancer cases and 17% of cancer-related deaths are attributable to obesity.
• 75% of the adult population are unaware of the relationship between obesity and cancer.
• Obese men and women were up to 52% and 62% more likely to develop and die from cancer, as compared to their normal-weight counterparts, respectively.
• Evidence suggests that individuals who are obese at the time of cancer diagnosis are at increased risk of cancer recurrence and mortality, compared to individuals of normal body weight.
• According to ICMR-INDIAB study 2015, prevalence rate of obesity and central obesity are varies from 11.8%-31.3% and 16.9%-36.3% respectively in India.

Measurement of Obesity

• Three simple measures of obesity are widely used in clinical practice; Body mass index(BMI), waist circumference(WC) and waist-to-hip circumference ratio (WHR).
• The most widely used method to define thinness and fatness is BMI.
• Abdominal obesity is defined by easy-to-use parameters like WC and WHR.
• WC Cut-offs for Asian Indians: Men: 78 cm, women: 72 cm.

Body mass index (BMI)

          Body mass index (BMI) is used to quantify body weight for height by indexing body weight (in kilograms)  divided by the square of height (in meters).
Calculate your BMI here

BMI in Indian population

          To some people the above heading might be confusing. Does BMI in Indian population(Asian population) is different from rest of world ? And the Answer is yes as Asian Indians exhibit unique features of obesity; excess body fat, abdominal adiposity, increased subcutaneous and intra-abdominal fat, and deposition of fat in ectopic sites (liver, muscle, etc.).

• From this we can see that Indians should consider weight management more seriously.

Associated cancer

• obesity is associated with an increased risk of developing 13 different types of cancer with sufficient strength of evidence in human
• The increased risk of malignancy associated with obesity is strongest in Endometrial cancer (relative risk, 7.1) followed by Esophagus (Adeno carcinoma) (relative risk, 4.8).

Mechanism of cancer occurrence

• Obesity is associated with metabolic alterations that may pose a biological link between body fatness and risk of cancer.
• Major hormonal pathways linking obesity and cancer risk include

1. Insulin and insulin-like growth factor-1 (IGF-1) axis- The insulin/IGF-1 axis has been implicated to play an important mediating role in the association between obesity and risk of pancreatic, colorectal and prostate cancer.
2. Sex-steroid hormones- Endogenous sex-steroid hormone concentrations, in particular obesity-associated pre-diagnostic elevations of estrogens and androgens, play an important role in postmenopausal breast cancer and endometrial cancer development.
3. Adipokines and chronic low-grade inflammation- The adipokines and adipocyte-mediated chronic low-grade inflammation represented by the acute-phase C-reactive protein may explain a substantial part of the association between obesity and risk of colorectal cancer.

• These pathways are interrelated with each other, and their importance varies by obesity-related cancer type.

Recommendation

• Guidelines recommend that

1. Individuals should achieve and maintain a healthy weight throughout life (e.g., avoid excess weight gain at all ages)
2. Be physically active (e.g., engage in 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity activity each week or a combination)
3. Eat a healthy diet. Put emphasis on plant foods, consume  ≥2.5 cups of fruits and vegetables each day, choose whole grains instead of refined-grain products
4. Limit alcohol intake (e.g., no more than one drink per day for women or no more than two drinks per day for men)

As body weight is modifiable, there is a potential for prevention of cancer.

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Refference

• Cancer : Principles & Practice of Oncology 11th edition, DeVita, Hellman, and Rosenberg
• Obesity and Cancer, Tobias Pischon, Katharina Nimptsch
• Ezzati M, Henley SJ, Lopez AD, Thun MJ (2005) Role of smoking in global and regional cancer epidemiology: current patterns and data needs. Int J Cancer 116:963–971
• de Martel C, Ferlay J, Franceschi S, Vignat J, Bray F, Forman D et al (2012) Global burden of cancers attributable to infections in 2008: a review and synthetic analysis. Lancet Oncol 13:607–615
• Parkin DM, Boyd L, Walker LC (2011) The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010. Br J Cancer 105(Suppl 2):S77–S81
• Whiteman DC, Webb PM, Green AC, Neale RE, Fritschi L, Bain CJ et al (2015) Cancers in Australia in 2010 attributable to modifiable factors: summary and conclusions. Aust NZ J Public Health 39:477–484
• MisraA, ChowbeyP, MakkarBM, et al. Consensus Statement for Diagnosis of Obesity, Abdominal Obesity and the Metabolic Syndrome for Asian Indians and Recommendations for Physical Activity, Medical and Surgical Management.
• Implications of the Revised Consensus Body Mass Indices for Asian Indians on Clinical Obstetric Practice, Aziz, J Clin Diagn Res. 2014 May; 8(5): OC01–OC03.