Body weight and cancer

After choosing not to smoke, keeping a healthy weight is the most important way you can reduce your risk of cancer.
 

Overweight and obesity is a major cause of cancer

After choosing not to smoke, keeping a healthy weight is the most important way you can reduce your risk of cancer. Having obesity clearly increases your risk of the following cancers:

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

Overweight and obesity in Ireland

Overweight and obesity levels have risen dramatically over the last 50 years. Most adults in Ireland now weigh more than they should.

  • Nearly two thirds (61 per cent) of all adults are overweight or obese
  • Nearly one quarter (23 per cent) of all adults are obese
  • Men are more likely to be overweight than women, but obesity rates are about the same

Most worrying is that 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.

But it’s not as simple as eating too much and moving too little. Obesity is a complex issue with many root causes, and one of the biggest influences is the world we live in.

  • Confusing food labels, and more fat, sugar and salt in our food make it harder to find healthy options.
  • Unhealthy food adverts
  • Checkout deals, bigger portions and fast food on the go all tempt us to eat more.

Free independent advice on weight loss: https://www.safefood.net/weight-loss  

How does being overweight increase my cancer risk?

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.

In summary, excess body fat is not harmless extra ‘padding’. It is active tissue which produces 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.

Waist size matters

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.  

Over 100 studies show that women who are overweight or obese and have been through the menopause have a higher risk of breast cancer.  Researchers believe that anywhere between 7 per cent and 15 per cent of breast cancer cases in developed countries are caused by obesity.

The relationship between obesity and breast cancer may be affected by the stage of life in which a woman gains weight and becomes obese. Researchers are working hard to answer this question. Weight gain during adult life, most often from about age 18 to between the ages of 50 or 60, has been linked with an increased risk of breast cancer after the menopause.

The increased risk of breast cancer in women who have had the menopause is thought to be due to increased levels of oestrogen in obese women. After the menopause, when the ovaries stop producing hormones, fat tissue becomes the most important source of oestrogen. Because obese women have more fat tissue, their oestrogen levels are higher. This potentially leads to more rapid growth of breast cancers that are encouraged to grow by the hormone oestrogen.

The relationship between obesity and breast cancer risk may also be affected by race and ethnicity. There is limited evidence that the risk associated with overweight and obesity may be less among Black and Hispanic women than among white women.

Overweight and obesity have been consistently linked with cancer of the lining of the womb (endometrial cancer). Obese and overweight women have two to four times the risk of getting this disease than women of a normal weight. This is regardless of whether they have been through the menopause or not. Many studies have also found that the risk of womb cancer increases when the weight is gained as an adult.

Although it has not yet clear why obesity is a risk factor for womb cancer, there is some evidence that diabetes plays a role, possibly in combination with low levels of physical activity. High levels of oestrogen produced by fat tissue are also likely to play a role.

Obesity is one of the most important causes of bowel cancer. Among men, a higher body mass index (BMI) is strongly associated with an increased risk of bowel cancer. Where the body fat is located appears to be an important factor, with extra fat stored around the waist (which can be worked out by waistline measurement) showing the strongest link with bowel cancer risk.

A link between BMI and waistline measurement with bowel cancer risk is also seen in women, but it is weaker. Researchers are considering a number of reasons why being overweight raises your chances of getting bowel cancer. The most likely cause is that high levels of insulin in obese people may encourage the development of bowel cancer.

In both men and women, obesity has been consistently linked with renal cell cancer, which is the most common form of kidney cancer. The reasons why obesity may increase renal cell cancer risk are not well understood. High levels of insulin may play a role in the development of the disease.

Overweight and obese people are about twice as likely as people of a healthy weight to develop a type of oesophageal cancer (cancer of the foodpipe) called oesophageal adenocarcinoma.

The reasons why obesity may increase the risk of oesophageal adenocarcinoma are not well understood. However, overweight and obese people are more likely than people of normal weight to have a history of gastric acid reflux, where stomach acid leaks out of the stomach and into the oesophagus. This damages the lining of the oesophagus and is linked with an increased risk of oesophageal adenocarcinoma.

Many studies have reported a slight increase in risk of pancreatic cancer in people who are overweight and obese. The amount of fat stored around the waist (which can be worked out by waistline measurement) is a particularly important factor in the link between overweight and obesity with pancreatic cancer.

The risk of gallbladder cancer increases with increasing body mass index (BMI). The increase in risk may be due to the increased incidence of gallstones in obese people. Gallstones are a strong risk factor for gallbladder cancer.

See more

The above information has been adapted from the National Cancer Institute.

Are you a healthy weight?

There are two ways of finding out if you are a healthy weight: Body mass index (BMI) Waistline measurement

Click here to use our BMI calculator, designed by Safefood.eu

Remember, though, BMI is not always an accurate measure if you are an athlete, pregnant or very short in height.

To measure your waistline:

  • 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.

You are at an increased risk of cancer if:

  • your waistline is greater than 94 cm or 37 inches for men
  • your waistline is greater than 81cm or 32 inches for women. 

Take control of your weight

Weight gain happens when you take in more energy than you use up. Losing weight is a gradual process which takes time. There are no quick fixes.

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 go hand-in-hand if you want to take control of your weight and reduce your risk of cancer.