Those who are overweight as a young adult may be at a greater risk of developing 18 cancers - more than the number previously linked with the disease - according to new study.
Earlier research identified a link between those who are overweight or obese with a heightened risk of diseases such as breast, bowel, kidney and pancreatic cancer.
And now carrying excess weight has been linked to leukaemia, non-Hodgkin lymphoma as well as bladder, head and neck cancers, even in never-smokers, in the large study. According to study authors, these cancers have not previously been "considered as obesity-related cancers ”, with the impact of obesity on cancer “likely underestimated”.
Published in Nature Communications, the new study involved the examination of health data on more than 2.6million Spanish adults aged 40 and under. All participants were cancer-free in 2009.
The researchers analysed the body-mass index (BMI) of those throughout the lifetime of those involved in the study, with the authors stating that previous studies only used one BMI score to identify the link.
Study participants were then tracked for nine years to see whether or not they developed cancer, with 225,399 diagnosed with a form of the disease during the study.
The researchers concluded that those who were overweight or obese in early adulthood, aged 40 and under, appeared to have an increased risk of cancer, with 18 cancers in total linked to excess weight.
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.”
Dr Heinz Freisling, from the International Agency for Research on Cancer and one of the study’s co-leaders, said: “The results of our study support a re-evaluation of the cancer burden associated with overweight and obesity, which currently is likely underestimated.”
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, said: “This study’s findings shed light on how body weight might relate to blood cancer risk, an area of emerging evidence that’s not yet fully understood.
“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.”
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