The European Obesity Summit, held in Gothenburg this year, featured presentations from international teams research the health impacts of obesity in childhood and later life.

In separate sessions, researchers from Bispebjerg and Frederiksberg Hospital, Copenhagen, and Oxford University presented their research linking high body mass index (BMI) to increased risks of colon cancer and aggressive prostate cancer.

Adult obesity is a well-established risk factor for colorectal cancer, however few studies have examined the possible association of the disease with childhood obesity. 

In a study of more than 250,000 people, Dr Britt Wang Jensen, Institute of Preventive Medicine; Bispebjerg and Frederiksberg Hospital, The Capital Region, Copenhagen, Denmark, and colleagues showed that children who have a higher body mass index at 13 years have an increased risk of colon cancer in adulthood. 

The researchers used the Copenhagen School Health Records Register to identify children who were born from 1930–1972 and had information on height and weight from their school health examinations, with their BMI transformed into z-scores (a method for comparing a child’s BMI to a reference population).

The team found that among 257,623 individuals (49.7% women), 2,676 were diagnosed with colon cancer (47.5% women) and 1,681 with rectal cancer (38.9% women).

For each z-score unit increase in BMI at age 13 years, there was a 9% increased risk of developing colon cancer in adulthood. To put this in perspective, compared to an average height and weight boy born in the late 1950s with a BMI of 17.8 kg/m2 (154.5 cm, 42.5 kg) another boy with a similar height but who weighed 5.9 kg more would have a 9% higher risk of colon cancer.

Results were essentially similar at all other ages (7 to 12 years).
 
The results were mainly driven by the association observed between BMI and cancers of the sigmoid colon (the part closest to the rectum – 1182 cases), each increase in BMI z-score at age 13 years increased the risk of that cancer by 11%. 

The authors concluded “BMI in childhood was associated with the later risk of colon cancer, whereas there were limited indications of associations with rectal cancer. These findings suggest that BMI in childhood may influence the risk of colon but not rectal cancer in adulthood. Since no information is available on adult BMI in the present study we cannot rule out that the results observed are due to continuation of large body size from childhood to adulthood. However, if this was the case we would expect to see an increasing risk of colon cancer with increasing age in childhood, which is not the case. It is possible that exposure to excess weight already from childhood increases the risk of colon cancer.”

In the second session, Dr Aurora Perez-Cornago, Cancer Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, UK, and colleagues presented a study of almost 150,000 men from 8 European countries, which showed higher BMI and waist circumference are associated with an increased risk of aggressive prostate cancer.

In this study, the authors investigated the associations between various body measurements at baseline, mainly BMI and waist circumference, and the risk of prostate cancer incidence, with a focus on tumour stage and grade, and on mortality from prostate cancer.

A total of 141,896 men with a mean age at recruitment of 52 years in 8 European countries (Italy, Spain, United Kingdom, the Netherlands, Greece, Germany, Sweden, and Denmark) from the EPIC cohort were included, and data were adjusted for education level, smoking, marital status, diabetes and physical activity.

After an average of 14 years of follow-up there were 7,022 incident cases of prostate cancer, of which 934 were fatal.  

Men with a higher BMI and waist circumference had an increased risk of high grade prostate cancer, an aggressive form of the disease (10% increased risk for BMI for every 5 kg/m² increase and 13% for waist circumference for every 10cm increase).
 
Furthermore, a 14% higher risk for fatal prostate cancer was observed for every 5 kg/m² increase in BMI, and 18% increased risk in every 10 cm increase in waist circumference.
 
The authors concluded “The findings from this large prospective study show that the association between body size and prostate cancer is complex and varies by disease aggressiveness; men who have greater adiposity have an elevated risk of high grade prostate cancer and prostate cancer death.”
 
They added “Our results are in line with health advice for other non-communicable diseases. Men should try to maintain a healthy weight.”