Being overweight linked to increased risk of 18 cancers in under 40s

Being overweight as a young adult can increase the risk of developing 18 cancers, new research suggests.

Previous studies have found that people who are overweight or obese have a heightened risk of several cancers, such as breast, bowel, kidney and pancreatic, but this list is now thought to be much larger.

Now, excess weight has also been linked to leukaemia and non-Hodgkin lymphoma, and among people who have never smoked, an increased risk of bladder, head and neck cancers.

The authors of the large new study, published in Nature Communications, said these cancers have previously not been considered as “obesity-related” diseases, and the impact of obesity on cancer is “likely underestimated”.

Researchers examined data on more than 2.6 million Spanish adults aged 40 and under who were cancer-free in 2009. They assessed the body mass index (BMI) scores throughout the lifetime of people involved with the study, saying that previous research investigating the link between weight and cancer has used single BMI scores. The people in the study were tracked for nine years to see whether they developed cancer, with some 225,396 being diagnosed during this period.

The Spanish researchers found that those who were overweight or obese in early adulthood – aged 40 and under – appeared to have an increased risk of cancer, while those who were overweight or obese for a longer period also appeared to have a higher risk. Overall, some 18 cancers were linked to excess weight.

The authors wrote: “This study shows that longer duration, greater degree, and younger age of onset of overweight and obesity during early adulthood are positively associated with risk of 18 cancers, including leukaemia, non-Hodgkin lymphoma, and among never-smokers, head and neck, and bladder cancers which are not yet considered as obesity-related cancers in the literature.

“Our findings seem to indicate that longer exposures to overweight and obesity (with or without accounting for the degree of overweight and obesity), as well as developing overweight and obesity at younger ages in early adulthood might increase cancer risk. Our findings support public health strategies for cancer prevention focusing on preventing and reducing early overweight and obesity.”

Commenting on the study, Dr Panagiota Mitrou, director of research, policy and innovation at World Cancer Research Fund, said: “This large study has future public health implications since additional cancers, such as leukaemia and non-Hodgkin lymphoma, have been shown to be linked with overweight and obesity.

“Our own evidence shows that maintaining a healthy weight throughout life is one of the most important things people can do to reduce their cancer risk, and early prevention in adulthood is key.”

Dr Suzanne Rix, research manager from the charity Blood Cancer UK, added that the study has helped shed light on how body weight may relate to blood cancer risk which could provide a better understanding as to how to prevent or treat the disease.

She said: “Researchers looked at participants’ body mass index (BMI) over their lifetime, not just at one point in time, and found potential links between being overweight or obese during early adulthood and blood cancers like leukaemia and non-Hodgkin lymphoma.

“It’s important to note this study can’t prove a direct cause between weight and blood cancer risk. The message to anyone who has been diagnosed with blood cancer is this: it is not your fault. Risk factors are not the same as causes and there are various risk factors for blood cancer that all interlink, with things like your age, sex and ethnicity playing an important role too.

“We must keep studying how weight and other factors are connected to blood cancer, as better understanding of this could help us develop ways to prevent or treat blood cancer, potentially saving lives.”