People with a high body mass index (BMI) are at an increased risk of developing 10 of the most common cancers, a major new study has found.

Using medical records, UK scientists identified over five million adults who did not have cancer. They were monitored for an average of five to seven years. The scientists assessed the risk of developing 22 of the most common cancers in relation to BMI.

This marked the largest study of BMI and cancer ever undertaken.

Almost 167,000 people developed one of these 22 common cancers during the follow-up period and a higher BMI was found to increase the risk of cancers of the colon, uterus, kidney, cervix, liver, thyroid, gallbladder, ovaries and breasts, as well as leukaemia.

Although when it came to breast cancer, the results appeared to apply more to post-menopausal breast cancer.

"There was a lot of variation in the effects of BMI on different cancers. For example, risk of cancer of the uterus increased substantially at higher BMI. For other cancers, we saw more modest increases in risk, or no effect at all.

"For some cancers like breast cancer occurring in younger women before the menopause, there even seemed to be a lower risk at higher BMI. This variation tells us that BMI must affect cancer risk through a number of different processes, depending on the cancer type," commented lead scientist, Dr Krishnan Bhaskaran, of the London School of Hygiene & Tropical Medicine.

The scientists estimated that in the UK alone, excess weight could account for as much as 41% of uterine cancers and 10% of colon, kidney and liver cancers.

"The number of people who are overweight or obese is rapidly increasing both in the UK and worldwide. It is well recognised that this is likely to cause more diabetes and cardiovascular disease. Our results show that if these trends continue, we can also expect to see substantially more cancers as a result," Dr Bhaskaran said.

Details of these findings are published in the journal, The Lancet.