National Obesity Forum - Higher body mass index means higher risk of several cancers

Dr Andrew Renehan from the University of Manchester and Christie Hospital NHS Foundation Trust and colleagues did a meta-analysis of 221 datasets incorporating 282,137 cases to determine the risk of cancer associated with a 5 kg/m2 increase in BMI. They found, in men, a 5 kg/m2 increase in BMI raised the risk of oesophageal adenocarcinoma by 52%, thyroid cancer by 33%, and colon and kidney cancers each by 24%. In women, a BMI increase of 5 kg/m2 increased the risk of endometrial (59%), gallbladder (59%), oesophageal adenocarcinoma (51%) and kidney (34%) cancers. They also noted weaker, but nonetheless significant, positive associations between increased BMI and rectal cancer and malignant melanoma in men; postmenopausal breast, pancreatic, thyroid, and colon cancers in women; and leukaemia, multiple myeloma, and non-Hodgkin’s lymphoma in both sexes. Associations were stronger in men than in women for colon cancer (24% versus 9%). And while associations were generally similar in studies from North America, Europe and Australia, and the Asia-Pacific region, a stronger association between increased BMI and both premenopausal and postmenopausal breast cancers was recorded in Asia-Pacific populations. These findings extend those reported by the World Cancer Research Fund last year, and those published by the UK Million Women’s study team in November 2007.

The authors concluded: “Increased BMI is associated with increased risk of common and less common malignancies. For some cancer types, associations differ between sexes and populations of different ethnic origins. These epidemiological observations should inform the exploration of biological mechanisms that link obesity with cancer.”

In an accompanying editorial, Dr Susanna Larsson and Professor Alicja Wolk from the Karolinska Institutet in Sweden, said: “The number of deaths per year attributable to obesity is about 30, 000 in the UK and ten times that in the USA, where obesity has been estimated to have overtaken smoking in 2005 as the main preventable cause of illness and premature death.”

They concluded: “Efforts will be needed to increase education on diet and physical activity, train health professionals, restrict advertisements of high-calorie and low-nutrient foods, limit access to unhealthy foods in schools and workplaces, levy taxes on sugary drinks and other foods high in calories, fat, or sugar, lower the prices of health foods, and promote physical activity in schools and workplaces. National cancer plans should include all these factors to reduce obesity, and thus decrease cancer incidence and increase survival.”

Dr David Haslam, Clinical Director of the National Obesity Forum, said: “The link between obesity and cancer has been observed for many years. This new data further underlines that obesity is a serious medical problem.”

National Obesity Chair Dr Colin Waine added: “ The government’s new obesity strategy will address some of the issues raised by the commentators from the Karolinska Institute that they, quite rightly, suggest are means of tackling the obesity epidemic. This new research throws the spotlight on the importance of continuing to recognise that treatment and funding for obesity management programmes is vital so that individuals affected receive appropriate professional treatment and management based on their risk factors.”