Body weight and cancer

Being overweight or having obesity clearly increases your risk of the following cancers:

• Bowel cancer
• Breast cancer
• Gallbladder cancer
• Kidney cancer
• Liver cancer
• Mouth, pharynx and larynx cancer
• Oesophageal cancer
• Ovarian cancer
• Pancreatic cancer
• Prostate cancer
• Uterine (womb) cancer

There is also growing evidence that being overweight could increase the risk of many other cancers, including:

• Thyroid cancer
• Brain tumours
• Leukaemia 
• Multiple myeloma 
• Non-Hodgkin lymphoma 

Overweight and obesity levels have risen dramatically over the last 50 years. 

• Most adults in Ireland now weigh more than they should.
• 63% of men and 50% of women in Ireland report being overweight or having obesity
• A quarter of 5–12 year olds are overweight or obese. Obesity in Irish children is higher than most other northern European countries, but similar to Britain.

Obesity is not as simple as eating too much and moving too little. It’s not a question of personal choice or willpower. Obesity is a complex issue, and one of the biggest influences is the world we live in. Some of the causes of obesity include: 

• Family circumstances
• Work demands of parents
• Affordability and availability of healthy food
• Education and health literacy
• Confusing food labels
• More fat, sugar and salt in our food 

Research has shown that the most likely cause is that fat cells release hormones that are linked with a higher risk of cancer. For example:

• Fat cells in your body make the hormone oestrogen and higher levels of oestrogen increase the risk of breast cancer (in women who have had the menopause) and womb cancer.
• Being overweight also increases the level of the hormone insulin in your body, which can encourage the growth of cancer cells. Higher levels of insulin are a common feature of many cancers, including bowel, kidney and pancreatic cancers.

Extra body fat is not harmless ‘padding’. It is active tissue that makes hormones that increase your risk of cancer.

Being overweight is also associated with:

• Gastric acid reflux: where stomach acid leaks out of the stomach and into the oesophagus. This damages the lining of the oesophagus and increases your risk of oesophageal cancer
• Gallstones: which increase your risk of gallbladder cancer.

Overweight people are also more likely to have a poor diet and be inactive, two other risk factors for cancer.

If you have an apple-shaped body, with fat stored around your waist, you have a higher chance of getting cancer than if you are pear shaped, where fat is stored at your hips and thighs. 

Simply put, extra fat stored around your waist puts you at greater risk. This is because fat cells in the upper part of the body appear to have different qualities from those found in the lower parts. 

To measure your waist:

• Place a tape measure around your waist at the narrowest point between the bottom of your ribs and the top of your hip bone.
• At this point, measure around your waist. Make sure the tape measure is snug but not marking your skin.
• Take the measurement at the end of your normal breath. 

Weight gain happens when you take in more energy than you use up. Being a healthy weight is about getting the balance right between what you eat and how active you are. To lose weight permanently, you will need to change the way you think about food and physical activity for good. 

Be realistic. For most people who are overweight, losing one or two pounds a week is excellent progress. Some weeks will be more difficult than others, the key is to keep going.

Eating for health and being active are the most important steps you can take to control of your weight and reduce your risk of cancer.