What do we know about body weight and cancer?

Welcome to our information pages on diet and its links to bowel, breast, stomach, oesophageal and mouth cancers. Follow the links to bring you to the relevant section:

What do we know about body weight and breast cancer?

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 African American and Hispanic women than among white women.

What do we know about body weight and cancer of the womb?

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.

What do we know about body weight and bowel cancer?

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.

What do we know about body weight and kidney 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.

What do we know about body weight and oesophageal cancer?

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.

What do we know about body weight and pancreatic cancer?

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.

What do we know about body weight and gallbladder 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

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