NIHR Signal Being overweight or having diabetes are both linked to cancer

Published on 6 February 2018

For western high-income countries such as the UK, an estimated 15% to 16% of cancers could be avoided by preventing diabetes, obesity or excess weight (defined as a Body Mass Index [BMI] greater than 25). A high BMI was responsible for almost twice as many cancers as diabetes.

Around 5.6% of cancers globally in 2012 were attributable to diabetes or high BMI. Because obesity is increasing globally, this number may rise by 25% by 2035.

Although the links between high BMI, diabetes and cancer have been known for some time, this study presents the first calculations of attributable risk for 175 countries. This represents the proportion of cancers that could be prevented if the risk factors were eliminated. 

The researchers call for more to be done to prevent obesity and diabetes.

Share your views on the research.

Why was this study needed?

Diabetes and high BMI are leading causes of death and ill health globally and are on the increase in most countries. In 2014, diabetes affected 9% of men and 8% of women. In 2016, worldwide 38.5% of men and 39.2% of women had high BMI, equivalent to around 2.01 billion adults. Rates are even higher in the UK: 65% of men and 58% of women in 2014 had high BMI.

The International Agency for Research on Cancer recognises a causal association between high BMI and 12 different cancers. High BMI is a risk factor for type 2 diabetes, which in turn is a risk factor for some cancers.

Given the rising levels of both high BMI and diabetes, this study aimed to estimate the impact of these conditions individually and together on cancer risk.

What did this study do?

This study uses previously published data, pooled from observational studies, on cancer risk associated with weight and diabetes. The 12 different cancers with the strongest association were chosen, and then the proportion of cancers of each type which could be attributed to diabetes or high BMI (the attributable risk) was calculated. The researchers collected data on the number of people with a BMI over 25 and diabetes in 2002 from 175 countries. They then looked at rates of cancer 10 years later in 2012.

The studies included in the meta-analyses for diabetes had applied rigorous adjustment to control for potential confounding factors, including BMI. This allowed the researchers to separate out the risk attributable to high BMI from that due to diabetes and also consider these risk factors acting together or independently.

What did it find?

  • A total of 5.6% of all incident cancers in 2012 were attributable to being overweight and having diabetes, corresponding to 792,600 new cases, although these findings fluctuate between groups of people, regions and cancers.
  • There were 187,600 (24.5%) of 766,000 cases of liver cancer and 121,700 (38.4%) of 317,000 cases of endometrial cancer attributable to diabetes and a high BMI.
  • Individually, having a high BMI (544,300 cases) was responsible for twice as many cancer cases as diabetes (280,100 cases).
  • 26.1% of diabetes-related cancers (77,000 cases), and 31.9% of high BMI related cancers (174,040 cases) might have been avoided if the prevalence of these risk factors had remained at levels from the 1980s.
  • Being overweight was estimated to cause 16.4% of cases of cancer in men and 15.0% in women in high-income western countries compared to 2.7% and 3.0% respectively in South Asia.

What does current guidance say on this issue?

The World Cancer Research Fund reports strong evidence for high BMI as a risk for developing 11 different types of cancer. Possible reasons include storing too much fat, which encourages the body to produce growth hormones which can promote the growth of cancer cells. Body fat also stimulates an inflammatory response, which may contribute to the development of several cancers.

The International Agency for Research on Cancer warns obesity is a risk factor for more cancer sites than previously established, reinforcing the benefits of maintaining a healthy body weight.

What are the implications?

The global average of 5.6% of cancers diagnosed in 2012 linked to weight and diabetes hides some variability between countries. For example, 38.2% of 792,600 cancer cases occurred in high-income western countries such as the UK.

This study provides the clear message that rising rates of excess BMI and diabetes may lead to increasing levels of certain cancers placing increasing strain on healthcare services everywhere.

The authors highlight population-based interventions to prevent and treat unhealthy weight and diabetes as a UK and global priority.

Citation and Funding

Pearson-Suttard J, Zhou B, Kontis V, et al. Worldwide burden of cancer attributable to diabetes and high body mass index: a comparative risk assessment. Lancet Diabetes Endocrinol. 2017. [Epub ahead of print].

This study was funded by the National Institute for Health Research and the Wellcome Trust.

Bibliography

NCD Risk Factor Collaboration (NCD-RisC). Worldwide trends in body-mass index, underweight, overweight, and obesity from 1975 to 2016: a pooled analysis of 2416 population-based measurement studies in 128·9 million children, adolescents, and adults. Lancet. 2017;390(10113):2627-42.

NHS England. Diabetes Prevention Programme patient pathway. London: NHS England; 2016.

NICE. Type 2 Diabetes prevention: population and community-level interventions. PH35. London: National Institute for Health and Care Excellence; 2011.

World Cancer Research Fund. Obesity, weight and cancer risk. London: World Cancer Research Fund; 2016.

World Health Organization. International Agency for Research on Cancer Identifies eight additional cancer sites linked to overweight and obesity. Press Release No. 247. Lyon: World Health Organization; 2016.

Why was this study needed?

Diabetes and high BMI are leading causes of death and ill health globally and are on the increase in most countries. In 2014, diabetes affected 9% of men and 8% of women. In 2016, worldwide 38.5% of men and 39.2% of women had high BMI, equivalent to around 2.01 billion adults. Rates are even higher in the UK: 65% of men and 58% of women in 2014 had high BMI.

The International Agency for Research on Cancer recognises a causal association between high BMI and 12 different cancers. High BMI is a risk factor for type 2 diabetes, which in turn is a risk factor for some cancers.

Given the rising levels of both high BMI and diabetes, this study aimed to estimate the impact of these conditions individually and together on cancer risk.

What did this study do?

This study uses previously published data, pooled from observational studies, on cancer risk associated with weight and diabetes. The 12 different cancers with the strongest association were chosen, and then the proportion of cancers of each type which could be attributed to diabetes or high BMI (the attributable risk) was calculated. The researchers collected data on the number of people with a BMI over 25 and diabetes in 2002 from 175 countries. They then looked at rates of cancer 10 years later in 2012.

The studies included in the meta-analyses for diabetes had applied rigorous adjustment to control for potential confounding factors, including BMI. This allowed the researchers to separate out the risk attributable to high BMI from that due to diabetes and also consider these risk factors acting together or independently.

What did it find?

  • A total of 5.6% of all incident cancers in 2012 were attributable to being overweight and having diabetes, corresponding to 792,600 new cases, although these findings fluctuate between groups of people, regions and cancers.
  • There were 187,600 (24.5%) of 766,000 cases of liver cancer and 121,700 (38.4%) of 317,000 cases of endometrial cancer attributable to diabetes and a high BMI.
  • Individually, having a high BMI (544,300 cases) was responsible for twice as many cancer cases as diabetes (280,100 cases).
  • 26.1% of diabetes-related cancers (77,000 cases), and 31.9% of high BMI related cancers (174,040 cases) might have been avoided if the prevalence of these risk factors had remained at levels from the 1980s.
  • Being overweight was estimated to cause 16.4% of cases of cancer in men and 15.0% in women in high-income western countries compared to 2.7% and 3.0% respectively in South Asia.

What does current guidance say on this issue?

The World Cancer Research Fund reports strong evidence for high BMI as a risk for developing 11 different types of cancer. Possible reasons include storing too much fat, which encourages the body to produce growth hormones which can promote the growth of cancer cells. Body fat also stimulates an inflammatory response, which may contribute to the development of several cancers.

The International Agency for Research on Cancer warns obesity is a risk factor for more cancer sites than previously established, reinforcing the benefits of maintaining a healthy body weight.

What are the implications?

The global average of 5.6% of cancers diagnosed in 2012 linked to weight and diabetes hides some variability between countries. For example, 38.2% of 792,600 cancer cases occurred in high-income western countries such as the UK.

This study provides the clear message that rising rates of excess BMI and diabetes may lead to increasing levels of certain cancers placing increasing strain on healthcare services everywhere.

The authors highlight population-based interventions to prevent and treat unhealthy weight and diabetes as a UK and global priority.

Citation and Funding

Pearson-Suttard J, Zhou B, Kontis V, et al. Worldwide burden of cancer attributable to diabetes and high body mass index: a comparative risk assessment. Lancet Diabetes Endocrinol. 2017. [Epub ahead of print].

This study was funded by the National Institute for Health Research and the Wellcome Trust.

Bibliography

NCD Risk Factor Collaboration (NCD-RisC). Worldwide trends in body-mass index, underweight, overweight, and obesity from 1975 to 2016: a pooled analysis of 2416 population-based measurement studies in 128·9 million children, adolescents, and adults. Lancet. 2017;390(10113):2627-42.

NHS England. Diabetes Prevention Programme patient pathway. London: NHS England; 2016.

NICE. Type 2 Diabetes prevention: population and community-level interventions. PH35. London: National Institute for Health and Care Excellence; 2011.

World Cancer Research Fund. Obesity, weight and cancer risk. London: World Cancer Research Fund; 2016.

World Health Organization. International Agency for Research on Cancer Identifies eight additional cancer sites linked to overweight and obesity. Press Release No. 247. Lyon: World Health Organization; 2016.

Worldwide burden of cancer attributable to diabetes and high body-mass index: a comparative risk assessment

Published on 28 November 2017

J Pearson-Stuttard, B Zhou, V Kontis, J Bentham, Marc Gunter, M Ezzati

The Lancet Diabetes & Endocrinology , 2017

Background Diabetes and high body-mass index (BMI) are associated with increased risk of several cancers, and are increasing in prevalence in most countries. We estimated the cancer incidence attributable to diabetes and high BMI as individual risk factors and in combination, by country and sex. Methods We estimated population attributable fractions for 12 cancers by age and sex for 175 countries in 2012. We defined high BMI as a BMI greater than or equal to 25 kg/m2. We used comprehensive prevalence estimates of diabetes and BMI categories in 2002, assuming a 10-year lag between exposure to diabetes or high BMI and incidence of cancer, combined with relative risks from published estimates, to quantify contribution of diabetes and high BMI to site-specific cancers, individually and combined as independent risk factors and in a conservative scenario in which we assumed full overlap of risk of diabetes and high BMI. We then used GLOBOCAN cancer incidence data to estimate the number of cancer cases attributable to the two risk factors. We also estimated the number of cancer cases in 2012 that were attributable to increases in the prevalence of diabetes and high BMI from 1980 to 2002. All analyses were done at individual country level and grouped by region for reporting. Findings We estimated that 5·6% of all incident cancers in 2012 were attributable to the combined effects of diabetes and high BMI as independent risk factors, corresponding to 792 600 new cases. 187 600 (24·5%) of 766 000 cases of liver cancer and 121 700 (38·4%) of 317 000 cases of endometrial cancer were attributable to these risk factors. In the conservative scenario, about 4·5% (626 900 new cases) of all incident cancers assessed were attributable to diabetes and high BMI combined. Individually, high BMI (544 300 cases) was responsible for twice as many cancer cases as diabetes (280 100 cases). 26·1% of diabetes-related cancers (equating to 77 000 new cases) and 31·9% of high BMI-related cancers (174 040 new cases) were attributable to increases in the prevalence of these risk factors from 1980 to 2002. Interpretation A substantial number of cancer cases are attributable to diabetes and high BMI. As the prevalence of these cancer risk factors increases, clinical and public health efforts should focus on identifying optimal preventive and screening measures for whole populations and individual patients. Funding NIHR and Wellcome Trust.

As well as published literature, calculations for the contribution of BMI and diabetes to cancer risk came from established sources, including the World Cancer Research Fund, and the International Agency for Research on Cancer. The number of cancers in each country was taken from GLOCOBAN, which is an interactive web-based platform presenting global cancer statistics to inform cancer control and research. Objective measures of weight, height and diabetes were taken from the NCD Risk Factor Collaboration. This is a global network of health scientists that provide rigorous and timely data on major risk factors for non-communicable diseases. This should have increased the reliability of the data and reduced the chance of recall bias.

Expert commentary

Many people are aware that obesity can increase their risk for type 2 diabetes and some cancers. But few may know that having type 2 diabetes combined with obesity increases cancer risk even more. ‘Getting cancer’ seems out of our control, but we can take steps to prevent it.

Those same steps can prevent obesity and type 2 diabetes. By finding effective ways to encourage people to eat a healthy diet and engage in regular physical activity, we can prevent not only obesity and type 2 diabetes, but also further reduce cancer risk.  

Janice L Thompson, Professor of Public Health Nutrition and Exercise, University of Birmingham