Obesity linked to more types of cancer
Obesity can increase the risk of more than 30 different types of cancer, according to a study.
Being overweight or obese was found to fuel the development of cancers that account for four in 10 of overall cases, a much greater proportion than previously thought.
The research, presented at the European Congress on Obesity in Venice, involved 4.1 million adults who were tracked over four decades. It confirmed established findings that obesity causes 13 types of cancer, including breast and bowel, and identified a further 19 types of cancer associated with weight gain, including some skin cancers and cervical cancer.
These forms of cancer make up 40% of all new cases. Until now, it was thought that only 25% of cases were obesity-related.
Although in most cases obesity is unlikely to be the direct cause, the study concluded that “a substantial proportion of cancers could potentially be prevented by keeping a normal weight”.
Every five-point increase in body mass index (BMI) was found to raise the risk of several common cancers by 24% in men and 12% in women. This is because fat cells send out signals that increase inflammation and make extra growth hormones, which increases the risk of tumours.
Obesity rates in the UK have doubled since the 1990s. The study shows that this is likely to lead to a “significant increase in cancer cases”.
The research was led by a team at Lund University in Sweden, who tracked 4.1 million adults for between 37 and 45 years, closely monitoring their weight. There were 332,500 cancers among the participants during this period. Researchers examined 122 types and subtypes to see if the risk increased significantly with higher BMI.
They found 32 types of cancer associated with obesity, more than twice the number identified in a report by the International Agency for Research on Cancer in 2016.
The 19 new types of cancer found to be linked to obesity include types of head and neck cancer, cervical cancer, malignant melanoma and gastric tumours.
Ming Sun, the lead researcher, said: “Our findings suggest that the impact of obesity on cancer might be greater than previously known, in that it is a risk factor for more cancers, especially of a rarer kind. Some of these have rarely or never before been investigated in relation to obesity.”