“Britain almost the worst in the world for obesity-fuelled cancer,” reports The Daily Telegraph. This and other headlines report on the outcome of an international study into the rate of obesity-related cancers...
“Britain almost the worst in the world for obesity-fuelled cancer,” reports The Daily Telegraph.
This and other headlines report on the outcome of an international study into the rate of obesity-related cancers.
The researchers estimated the proportion of cases of cancer overall, and the proportion of specific cancers already associated with obesity, that are likely to have been caused by obesity worldwide.
They based their estimates on previous research indicating the relative risk of obesity causing cancer, and using population data to calculate the number of people who are overweight or obese.
Overall, they estimated that 3.6% of cancers in adults (aged over 30) worldwide are caused by high body mass index (BMI), with the proportion attributed to obesity slightly higher in women than in men. In the UK, 4.4% of all cases of cancer per year in men and 8.2% of all cases of cancer per year in women were estimated to be attributable to obesity.
The research focused on cancers the World Cancer Research Fund (WCRF) has already established are linked to high BMI. When looking at these cancers, the UK was joint second highest in the world for the estimated proportion of these cancers that were attributed to obesity. The US had the highest rates.
Being overweight or obese is associated with an increased risk of some cancers and increases the risk of diabetes and cardiovascular disease, such as heart attack and stroke.
Why can obesity trigger cancer?
There are a number of possible ways obesity can cause cancer:
- fat tissue produces an excess amount of certain hormones that may disrupt normal cell growth
- obesity may lead to tissue inflammation, which may increase the risk of them turning cancerous
- fat cells may interfere with the actions of proteins that are designed to regulate cell growth
Where did the story come from?
The study was carried out by researchers from the International Agency for Research on Cancer in Lyon, and several universities around the world. It was funded by the World Cancer Research Fund International, the Marie Curie Intra-European Fellowship from the European Commission, the US National Institutes of Health, the Australian National Health and the Medical Research Council.
The study was published in the peer-reviewed medical journal the Lancet Oncology.
The media in general reported the story accurately, with particular emphasis on the UK results.
What kind of research was this?
This was a population study that aimed to estimate the number of global cases of cancer which could be attributable to high BMI. The researchers intended that the results be used to help inform public health policy to reduce the global burden of cancer.
High BMI of 25 or more (overweight) is associated with increased risk of a number of chronic diseases and mortality. The authors report that recent statistics show 35% of the global adult population (20 years and older) are overweight and 12% are obese (BMI of 30 or more).
According to the WCRF, there is sufficient evidence to show that high BMI is associated with an increased risk of the following cancers:
- oesophageal (food pipe) adenocarcinoma (cancer of the mucus-producing cells)
- colon (large bowel)
- gallbladder (in women)
- postmenopausal breast
- endometrial (lining of the womb)
What did the research involve?
For each country, the researchers estimated the average adult’s BMI from 2002. To provide a substantial enough time for the obesity to have had the potential to increase the risk of cancer, they used the 2012 global figures for cancer incidence. Using previously researched relative risk estimates of how much high BMI increases the risk of each of the cancers listed above, they estimated the number of cancer cases that could be attributed to high BMI.
What were the basic results?
The researchers estimated that worldwide, 481,000 adults aged 30 years or older were diagnosed in 2012 (3.6% of cases) due to high BMI. The proportion of all cancer cases that were attributed to high BMI were more than twice as frequent for women: 345,000 cases (5.4%), compared to 136,000 cases for men (1.9%).
In the UK, 4.4% of all cases of cancer per year in men (7,217), and 8.2% of all cases of cancer per year in women (13,037) were estimated to be attributable to obesity. Men in the UK had the joint fourth highest proportion of cancers attributable to high BMI with Malta (4.4%), behind the Czech Republic (5.5%), Jordan (4.5%) and Argentina (4.5%).
When focusing on the above list of cancers the WCRF associated with high BMI, obesity was attributed to 20% of these cancers in men and 15% of these cancers in women. The only country with a higher proportion was the US, at 21% for men and 20% for women.
The percentage of high BMI-related cancers attributed to obesity were:
- oesophageal cancer: 44% for men and women
- colon 19% for men, 10% for women
- rectum 10% for men, 5% for women
- pancreas 13% for men, 10% for women
- kidney 23% for men, 31% for women
For women only:
- gallbladder 50%
- postmenopausal breast 12%
- womb 43%
- ovary 6%
How did the researchers interpret the results?
In conclusion, the authors say “these findings emphasise the need for a global effort to abate the increasing numbers of people with high BMI. Assuming that the association between high BMI and cancer is causal, the continuation of current patterns of population weight gain will lead to continuing increases in the future burden of cancer”.
This international study has shown alarming increases in cases of cancer that can be attributed to high BMI.
Overall, they estimated that 3.6% of cancers in adults (aged over 30 years) worldwide are caused by high BMI, with the proportion attributed to obesity slightly higher in women than in men. In the UK, 4.4% of all cases of cancer per year in men and 8.2% of all cases of cancer per year in women, were estimated to be attributable to obesity.
The research focused on cancers that the WCRF has already established are linked to high BMI. When looking at these cancers, the UK was joint second highest in the world for the estimated proportion of these cancers that were attributed to obesity. The US had the highest rates.
Being overweight or obese is associated with an increased risk of some cancers, diabetes, and cardiovascular disease such as heart attack and stroke.
There are many different ways to tackle overweight and obesity, and a good start is the NHS Choices weight loss plan.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.