Being overweight is the UK's biggest preventable cause of cancer after smoking, according to CRUK.5 More than 1 in 20 cancers in the UK are believed to be linked to being overweight or obese, with bowel and breast cancers the leading types of cancer associated with being overweight.10

Other types of cancer, which are more common in people who are overweight or obese, are cancer of the womb, kidney, oesophagus, pancreas, liver, upper stomach (gastric cardia), gallbladder, ovaries, thyroid, blood plasma cells (myeloma), and the brain in the form of meningioma. The relationship and impact of excess body weight and some of these cancers is still being assessed.
A recent CRUK blog pointed out that reducing the risk of cancer by losing weight may not have as profound an effect on risk reduction as hoped. While losing weight decreases risk, and keeping weight off stops risk accumulating, risk is also related to the length of time someone has been overweight. Put simply, €never gaining extra weight in the first place is still best for reducing cancer risk.€11
Unfortunately, the evidence cited from research looking at intentional weight loss and cancer risk reduction tends to be based on relatively small studies. Nor is the mode of action of weight loss on cancer risk reduction fully understood, but changes in the levels of hormones and inflammatory mediators seem to be significant.
Losing weight and then maintaining that weight loss is very difficult, which is why CRUK is one of several organisations supporting public health measures such as the sugary drinks tax to €make healthy choices easy for everyone, both to prevent weight gain, and to help those lose it who need to.€