Increased body mass index (BMI) increases the risk of common and less common cancers, and the level of risk can vary between the sexes and different ethnic groups depending on the type of cancer. These are the conclusions of authors of an Article in this week's edition of The Lancet.
Excess bodyweight, whether in people who are overweight (BMI of 25-29.9kg/m2) or obese (BMI of 30kg/m2) is increasingly recognised as an important risk factor for some common cancers. Dr Andrew Renehan, University of Manchester and Christie Hospital NHS Foundation Trust, Manchester, UK, and colleagues did a meta-analysis (a combined analysis of previous studies) of 221 datasets incorporating 282137 cases to determine the risk of cancer associated with a 5kg/m2 increase in BMI.
The researchers found in men, a 5kg/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 5kg /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.
They also found 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 conclude: "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 Comment, Dr Susanna Larsson and Professor Alicja Wolk, Division of Nutritional Epidemiology, National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden, say: "The number of deaths per year attributable to obesity is about 30000 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 conclude: "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."
For Dr Andrew Renehan, University of Manchester Christie Hospital NHS Foundation Trust, Manchester, UK, please contact Alicia Custis, Head of Communications, The Christie Hospital NHS Foundation Trust, Manchester, UK T) +44 (0) 161 446 3706 / +44 (0) 7899 797065 E) arenehan@picr.man.ac.uk / Alicia.Custis@christie.nhs.uk
Dr Susanna Larsson, Division of Nutritional Epidemiology, National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden T) +46 8 524 860 59 E) susanna.larsson@ki.se
http://multimedia.thelancet.com/pdf/press/bodymass.pdf
Journal
The Lancet