Obesity and Cancer

What’s my risk of developing cancer if I’m overweight or obese?

Being overweight doesn’t mean that someone will definitely develop cancer. But if a person is overweight they are more likely to get cancer than if they are a healthy weight.

We can help stack the odds against cancer by losing weight or avoiding gaining more weight.

People keeping a healthy weight could prevent around 22,800 cases of cancer every year in the UK.  

How can overweight and obesity cause cancer?

  • Yes, overweight and obesity is the second biggest preventable cause of cancer in the UK- more than 1 in 20 cancer cases are caused by excess weight
  • The risk is higher the more weight a person gains and the longer they are overweight for
  • The good news is small changes that are kept up over time can make a real difference

Extra fat in the body doesn’t just sit there, its active, sending out signals to the rest of your body. These signals can tell cells in our body to divide more often, which can lead to cancer.

Scroll down to find out more about the science…

What types of cancer are caused by excess weight?

Breast (in women after the menopause), bowel, womb, oesophageal (food pipe), pancreatic, kidney, liver, upper stomach (gastric cardia), gallbladder, ovarian, thyroid, myeloma (a type of blood cancer), and meningioma (a type of brain tumour).

This includes 2 of the most common types of cancer – breast and bowel cancers – and 3 of the hardest to treat – pancreatic, oesophageal and gallbladder cancers.

Firstly, what does fat do in the body?

It has 2 main functions;

  • acts as a store of energy
  • constantly sending messages to the rest of your body which affect things like cell growth, chemical reactions in cells, and the body’s reproductive cycles.

So fat is active, telling other cells what to do. And if there is too much fat in the body, then the signals it sends around the body can cause damage.

These signals affect;

  • Growth hormones- too much body fat can cause levels of insulin and other growth factors to rise, which can tell cells to divide more often. This raises the chance that cancer cells will develop.
  • Inflammation- when there are more fat cells in the body, specialised immune cells go to the area, possibly to remove dead and dying fat cells. This can lead to inflammation. Then cells divide faster, and when this happens over a long time it can raise the risk of cancer.
  • Sex hormones- after the menopause, oestrogen made by fat cells can make cells divide faster in the breasts and womb (two of the cancer types most closely linked to obesity), increasing the risk of cell faults and cancer.

These are the main ways scientists have identified so far, but research continues to find out more about the ways extra body fat can cause cancer.

Does it matter where the fat is stored in the body?

Yes, it can. When too much fat is carried around the belly, it can do even more damage. So-called ‘apple’ shapes are linked to bowel, kidney, oesophageal, pancreatic, and breast cancers.

It isn’t clear exactly why this is, but it could be to do with how quickly certain chemicals from fat can get into the blood.

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