Bodyweight facts and evidence

Read the key facts about obesity and cancer risk, and find the supporting evidence from academic research and scientific studies to see why we say what we do.

Cancer Research UK and Weight Concern teamed up to develop a programme to help people keep a healthy weight. The tips are based on research and scientific evidence [1].

One study looked at the effect of giving the Ten Top Tips leaflet to people trying to lose weight [1]. Eight weeks later, people who had used the leaflet had lost an average of 2 kg, compared to 0.4 kg in those who didn’t receive the leaflet. After eight months, people using the leaflet had lost an average of 3.8 kg, and also reported an improvement in quality of life.

A small study of people using the Ten Top Tips leaflet also found that initially, it was an effort to remember to use some of the tips, but that over time it got easier to remember to follow the tips, until they became automatic [2].

In general, it takes different people different amounts of time to develop habits like those suggested in the Ten Top Tips [3].

Evidence shows that making small, simple changes can develop into healthy habits that have a long-term impact on behaviour and health [4].

References

1. Lally, P., Chipperfield, A. & Wardle, J. Healthy habits: efficacy of simple advice on weight control based on a habit-formation model. International journal of obesity 32, 700–7 (2008). View summary on PubMed

2. Lally, P., Wardle, J. & Gardner, B. Experiences of habit formation: a qualitative study. Psychology, health & medicine 16, 484–9 (2011). View summary on PubMed

3. Lally, P., van Jaarsveld, C. H. M., Potts, H. W. W. & Wardle, J. How are habits formed: Modelling habit formation in the real world. European Journal of Social Psychology 40, 998–1009 (2010). View resource

4. Lally, P. & Gardner, B. Promoting habit formation. Health Psychology Review 7, S137–S158 (2013). View resource

Major studies confirm that being overweight or obese increases the risk of various cancers [5-8]. The World Health Organisation (WHO) says that overweight and obesity are the most important known avoidable causes of cancer after tobacco [9].

One of the largest studies on excess weight and cancer to date looked at GP records of more than 5 million people and the 22 most common cancer sites. This single study found a link between weight and 10 different types of cancer, including bowel, kidney and cervical cancer [10].  Researchers estimate that overweight and obesity are behind around 18,000 cases of cancer each year in the UK [11].  

The latest statistics for England show that around 60% of adults are overweight or obese [12], and the figures are similar in the other UK nations [12]–[15]. A recent report by Cancer Research UK and the UK Health Forum predicts three in four adults will be overweight or obese by 2035, if current trends continue [16]. This could lead to an extra 670,000 cases of cancer in the UK over the next twenty years.

References

5. Bianchini, F., Kaaks, R. & Vainio, H. Overweight, obesity, and cancer risk. The Lancet Oncology 3, 565–574 (2002). View summary on PubMed

6. International Agency for Research on Cancer (IARC). Weight Control and Physical Activity. IARC Handbooks of Cancer Prevention/ World Health Organization, International Agency for Research on Cancer 6, 1–315 (2002). View resource

7. Renehan, A. G., Tyson, M., Egger, M., Heller, R. F. & Zwahlen, M. Body-mass index and incidence of cancer: a systematic review and meta-analysis of prospective observational studies. The Lancet 371, 569–78 (2008). View summary on PubMed

8. Reeves, G. K. et al. Cancer incidence and mortality in relation to body mass index in the Million Women Study: cohort study. BMJ 335, 1134 (2007). View summary on PubMed

9. World Health Organization. Report of a Joint WHO / FAO Expert Consultation on Diet, Nutrition and the Prevention of Chronic Diseases. 160 (2003). View resource

10. Bhaskaran K., et al. Body-mass index and risk of 22 specific cancers: a population-based cohort study of 5-24 million UK adults. Lancet, vol. 384, no. 9945, pp. 755–765, 2014. View resource

11. Parkin, D. M. & Boyd, L. 8. Cancers attributable to overweight and obesity in the UK in 2010. British journal of cancer 105 Suppl, S34–7 (2011). View summary on PubMed

12. Scottish Government Statistician Group. Obesity Indicators 2013: Monitoring Progress for the Prevention of Obesity Route Map (2013). View resource

13. Welsh Government. Welsh Health Survey 2012 (2012). View resource

14. Department of Health, Social Services and Public Safety. Health survey Northern Ireland 2010/11 - Obesity Analysis (2010). View resource

15. Health and Social Care Information Centre. Statistics on Obesity , Physical Activity and Diet: England 2014. (2014). View resource

16. Cancer Research UK and UK Health Forum: Tipping the scales (2016) View resource

 

Scientists have estimated that anywhere between 7% and 15% of breast cancer cases in developed countries are caused by obesity [11], [17]–[19]. Over a hundred studies show that women who are overweight or obese and have been through the menopause have higher breast cancer risks [7], [18], [19].

Two large studies funded by Cancer Research UK - the EPIC study and the Million Women Study - have found that obese women have a 30% higher risk of postmenopausal breast cancer than women with a healthy weight [8], [19]. Obesity does not increase the risk of breast cancer in women before their menopause [7], [8], [19].Putting on weight over time can also increase the risk of breast cancer. Studies have found that:

  • putting on 25 kg (55 lb) after the age of 18 increases the risk of postmenopausal breast cancer by 45% [17].
  • putting on 2-10 kg (4.4 - 22 lb) after the age of 50 increases the risk of postmenopausal breast cancer by 30% [20].

Changes in a woman’s waist circumference before the menopause may affect her risk of breast cancer after the menopause, independently of her weight. A study in 2014 found women whose skirt size increased by one unit (from a size 12 to 14, for example) every decade between the age of 25 and postmenopausal age had a 33% increased risk of breast cancer after their menopause [21].

The size of a woman’s waist after the menopause could also affect her risk of breast cancer. A study in 2015 found women with a waist circumference over 88cm had a 30% increased risk of breast cancer compared to women with a waist circumference below 80cm, irrespective of how much she weighed [22]. But this study looked at women with sisters who had been previously diagnosed with breast cancer, so they may already have been at increased risk of breast cancer. 

References

7. Renehan, A. G., Tyson, M., Egger, M., Heller, R. F. & Zwahlen, M. Body-mass index and incidence of cancer: a systematic review and meta-analysis of prospective observational studies. The Lancet 371, 569–78 (2008). View summary on PubMed

8. Reeves, G. K. et al. Cancer incidence and mortality in relation to body mass index in the Million Women Study: cohort study. BMJ 335, 1134 (2007). View summary on PubMed

11. Parkin, D. M. & Boyd, L. 8. Cancers attributable to overweight and obesity in the UK in 2010. British journal of cancer 105 Suppl, S34–7 (2011). View summary on PubMed

17. Eliassen, H. A., Colditz, G. A., Rosner, B., Willett, W. C. & Hankinson, S. E. Adult weight change and risk of postmenopausal breast cancer. JAMA : the journal of the American Medical Association 296, 193–201 (2006). View summary on PubMed

18. Renehan, A. G., Soerjomataram, I. & Leitzmann, M. F. Interpreting the epidemiological evidence linking obesity and cancer: A framework for population-attributable risk estimations in Europe. European journal of cancer (Oxford, England : 1990) 46, 2581–92 (2010). View summary on PubMed

19. Lahmann, P. H. et al. Body size and breast cancer risk: findings from the European Prospective Investigation into Cancer And Nutrition (EPIC). International journal of cancer. Journal international du cancer 111, 762–71 (2004). View summary on PubMed

20. Ahn, J. et al. Adiposity, adult weight change, and postmenopausal breast cancer risk. Archives of internal medicine 167, 2091–102 (2007). View summary on PubMed

21. Fourkala, E. et al. Association of skirt size and postmenopausal breast cancer risk in older women: a cohort study within the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) BMJ, pp. 1–10 (2014) View resource

22. White, A. J., et al. Overall and Central Adiposity and Breast Cancer Risk in the Sister Study.Cancer (2015) View summary on PubMed

Obesity is one of the most important causes of bowel cancer [6], [11], [23]. Some groups have estimated that being overweight or obese causes about 11-14% of bowel cancer cases [11], [24]–[26].

Many large studies have found that bowel cancer is more common in overweight or obese people [27]–[31]. Two of the largest studies so far, including the EPIC study, have found that obese men have about 50% higher risks of bowel cancer than those with a healthy weight [29], [30].

A recent analysis of studies looking at weight change and colorectal cancer risk found people had a 3% increased risk of colorectal cancer for every 5kg they gained in weight between early adulthood and midlife [32].

When BMI is used to measure body fat, studies tend to find that only obese men have a higher risk of bowel cancer. When it comes to waist circumference or waist-to-hip ratio, it’s not clear whether men or women, or both, have a higher risk. Some studies have linked waist circumference to higher risks of bowel cancer in both men and women [30], [33]. But another study found a bigger waist circumference and waist-to-hip ratio was associated with higher risk of colorectal cancer in men only [34]. However this study looked at nurses and other health professionals, who often lead healthy lifestyles, so it will not be representative of the general population. Together these studies suggest that fat around the stomach is more of a problem than fat elsewhere on the body.

References

6. International Agency for Research on Cancer (IARC). Weight Control and Physical Activity. IARC Handbooks of Cancer Prevention/ World Health Organization, International Agency for Research on Cancer 6, 1–315 (2002).View resources

11. Parkin, D. M. & Boyd, L. Cancers attributable to overweight and obesity in the UK in 2010. British journal of cancer 105 Suppl, S34–7 (2011). View summary on PubMed

12. Scottish Government Statistician Group. Obesity Indicators 2013: Monitoring Progress for the Prevention of Obesity Route Map (2013) View resource

23. WHO Technical Report Series. Diet, nutrition and the prevention of chronic diseases (2003). View resource

24. Danaei, G. et al. Causes of cancer in the world: comparative risk assessment of nine behavioural and environmental risk factors. The Lancet 366, 1784–93 (2005). View summary on PubMed

25. Boyle, P. et al. European Code Against Cancer and scientific justification: third version (2003). Annals of oncology : official journal of the European Society for Medical Oncology / ESMO 14, 973–1005 (2003). View summary on PubMed

26. Renehan, A. G. et al. Incident cancer burden attributable to excess body mass index in 30 European countries. International journal of cancer. Journal international du cancer 126, 692–702 (2010). View summary on PubMed

27. Renehan, A. G., Tyson, M., Egger, M., Heller, R. F. & Zwahlen, M. Body-mass index and incidence of cancer: a systematic review and meta-analysis of prospective observational studies. The Lancet 371, 569–78 (2008). View summary on PubMed

28. Larsson, S. C. & Wolk, A. Obesity and colon and rectal cancer risk: a meta-analysis of prospective studies. The American journal of clinical nutrition 86, 556–65 (2007). View summary on PubMed

29. Adams, K. F. et al. Body mass and colorectal cancer risk in the NIH-AARP cohort. American journal of epidemiology 166, 36–45 (2007). View summary on PubMed

30. Pischon, T. et al. Body size and risk of colon and rectal cancer in the European Prospective Investigation Into Cancer and Nutrition (EPIC). Journal of the National Cancer Institute 98, 920–31 (2006). View summary on PubMed

31. Ma, Y. et al. Obesity and risk of colorectal cancer: a systematic review of prospective studies. PloS one 8, e53916 (2013). View summary on PubMed

32. Karahalios, A., English, D. R. and Simpson, J. A. Weight change and risk of colorectal cancer: a systematic review and meta-analysis. Am. J. Epidemiol., vol. 181, no. 11, pp. 832–845 (2015) View summary on PubMed

33. Aleksandrova, K. et al. Adiposity, mediating biomarkers and risk of colon cancer in the European Prospective Investigation into Cancer and Nutrition study. Int. J. cancer, vol. 621, no. May 2013, pp. 612–621 (2014) View summary on PubMed

34. Song, M. et al. Long-term status and change of body fat distribution, and risk of colorectal cancer: a prospective cohort study. Int. J. Epidemiol., vol. 45 (2) (2015) View summary on PubMed

 

Excess body weight is one of the most important causes of womb cancer. A 2011 study estimated that more than a third of womb cancers in the UK are caused by being overweight or obese [11].

Studies have consistently found that obese people are two to three times more likely to develop womb cancer than people with a healthy bodyweight [8], [18], [35], [36]. 

References

8. Reeves, G. K. et al. Cancer incidence and mortality in relation to body mass index in the Million Women Study: cohort study. BMJ 335, 1134 (2007). View summary on PubMed

11. Parkin, D. M. & Boyd, L. 8. Cancers attributable to overweight and obesity in the UK in 2010. British journal of cancer 105 Suppl, S34–7 (2011). View summary on PubMed

18. Renehan, A. G., Soerjomataram, I. & Leitzmann, M. F. Interpreting the epidemiological evidence linking obesity and cancer: A framework for population-attributable risk estimations in Europe. European journal of cancer (Oxford, England : 1990) 46, 2581–92 (2010). View summary on PubMed

35. Bjørge, T., Engeland, A., Tretli, S. & Weiderpass, E. Body size in relation to cancer of the uterine corpus in 1 million Norwegian women. International journal of cancer. Journal international du cancer 120, 378–83 (2006). View summary on PubMed

36. Jenabi, E. and Poorolajal, J. The effect of body mass index on endometrial cancer: a meta-analysis. Public Health, vol. 129, no. 7, pp. 872–880 (2015) View summary on PubMed

Being overweight or obese increases the risk of a type of oesophageal cancer (cancer of the foodpipe) called “oesophageal adenocarcinoma” [11].

Overweight people are over 80% more likely to develop this cancer than people of a healthy weight, and the risk in obese people is even more [37].

Experts have estimated that in the UK it causes about 1 in 5 cases of this type of cancer [11]. In fact, the rates of oesophageal adenocarcinoma in the UK are among the highest in the world, especially in men [38]. Some studies have suggested that, in Western countries, this type of cancer may be becoming more common because of rising levels of obesity [37], [39], [40].

Some studies have shown obese children may be at higher risk of oesophageal cancer later in life. One study in 2015 found adults with high BMIs in childhood had an increased risk of oesophageal adenocarcinoma in adulthood [41]. But it’s hard to be sure if high BMI in childhood increased their risk of this type of cancer when they were older, or whether the link was found simply because obese children are more likely to grow into obese adults [42].

We discuss the evidence for a link between childhood obesity and oesophageal cancer in adulthood in more detail on the Cancer Research UK blog.

 

References

11. Parkin, D. M. & Boyd, L. 8. Cancers attributable to overweight and obesity in the UK in 2010. British journal of cancer 105 Suppl, S34–7 (2011). View summary on PubMed

37. Turati, F., Tramacere, I., La Vecchia, C. & Negri, E. A meta-analysis of body mass index and esophageal and gastric cardia adenocarcinoma. Annals of oncology : official journal of the European Society for Medical Oncology / ESMO 24, 609–17 (2013). View summary on PubMed

38. The Cancer Research UK Statistical Information Team. European Age-Standardised rates. GLOBOCAN 2008 v1.2, IARC, version 1.2 (2011). View resources

39. Kubo, A. & Corley, D. A. Body mass index and adenocarcinomas of the esophagus or gastric cardia: a systematic review and meta-analysis. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 15, 872–8 (2006). View summary on PubMed

40. Merry, A. H. H., Schouten, L. J., Goldbohm, R. A. & van den Brandt, P. a. Body mass index, height and risk of adenocarcinoma of the oesophagus and gastric cardia: a prospective cohort study. Gut 56, 1503–11 (2007). View summary on PubMed

 

Higher BMI and fat around the belly are both linked to a 10-14% increased risk of pancreatic cancer in men and women [8], [49]–[51]. We don’t have clear evidence about exactly why this is, but it may be linked to some of the changes in hormone levels that are caused by obesity [50], [51].

The risk increases with higher BMI, and it is estimated that around one out of ten pancreatic cancers may be caused by being overweight or obese [11]. Excess weight at all ages – from early adulthood through midlife to old age – has been associated with an increased risk of pancreatic cancer [52]. Those who are overweight when they are younger and gain more weight as they get older are at around 50% higher risk than those who keep a healthy weight from the age of 18 [53]. 

References

8. Reeves, G. K. et al. Cancer incidence and mortality in relation to body mass index in the Million Women Study: cohort study. BMJ 335, 1134 (2007). View summary on PubMed

11. Parkin, D. M. & Boyd, L. 8. Cancers attributable to overweight and obesity in the UK in 2010. British journal of cancer 105 Suppl, S34–7 (2011). View summary on PubMed

49. Aune, D. et al. Body mass index, abdominal fatness and pancreatic cancer risk: a systematic review and non-linear dose-response meta-analysis of prospective studies. Annals of oncology : official journal of the European Society for Medical Oncology / ESMO 23, 843–52 (2012). View summary on PubMed

50. World Cancer Research Fund. Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. 537 (AICR, 2007). View resource

51. World Cancer Research Fund. Food, nutrition, physical activity and the prevention of pancreatic cancer (2012) View resource

52. Stolzenberg-Solomon, R. Z. et al. Adiposity, physical activity, and pancreatic cancer in the National Institutes of Health-AARP Diet and Health Cohort. Am. J. Epidemiol., vol. 167, no. 5, pp. 586–97 (2008) View summary on PubMed

53. Genkinger, J. M. et al. A pooled analysis of 14 cohort studies of anthropometric factors and pancreatic cancer risk. International journal of cancer. Journal international du cancer 129, 1708–17 (2011) View summary on PubMed

Studies have estimated that having a high body weight accounts for nearly a quarter of kidney cancers [11], [26]. And many studies have consistently shown that higher BMI is linked to an increased risk of kidney cancer [8], [50], [54]–[57].

The most recent analysis of studies on weight and kidney cancer by the World Cancer Research Fund confirmed greater body weight is a convincing cause of kidney cancer [56]. The report found that higher BMI, waist circumference, and waist-to-hip ratio all increase the risk of kidney cancer. This risk increases by 30% with each 5 BMI units a person gains, and by 11% with each extra 10cm of fat around gained around the waist. 

 

References

8. Reeves, G. K. et al. Cancer incidence and mortality in relation to body mass index in the Million Women Study: cohort study. BMJ 335, 1134 (2007). View summary on PubMed

11. Parkin, D. M. & Boyd, L. 8. Cancers attributable to overweight and obesity in the UK in 2010. British journal of cancer 105 Suppl, S34–7 (2011). View summary on PubMed 

26. Renehan, A. G. et al. Incident cancer burden attributable to excess body mass index in 30 European countries. International journal of cancer. Journal international du cancer 126, 692–702 (2010). View summary on PubMed

50. World Cancer Research Fund/ American Institute for Cancer Research. Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. 537 (AICR, 2007). View resource

54. Bergström, A. et al. Obesity and renal cell cancer--a quantitative review. British journal of cancer 85, 984–90 (2001) View summary on PubMed

55. Wang, F. and Xu, Y. Body mass index and risk of renal cell cancer: A dose-response meta-analysis of published cohort studies. International Journal of Cancer. vol. 1686, pp. 1673–1686 (2014) View summary on PubMed

56. World Cancer Research Fund. Diet, nutrition, physical activity and kidney cancer (2015) View resource

57. Pischon, T. et al. Body size and risk of renal cell carcinoma in the European Prospective Investigation into Cancer and Nutrition (EPIC) International Journal of Cancer. vol. 738 pp. 728-738 (2006) View summary on PubMed

The WCRF report that obesity is a convincing cause of liver cancer [58]. This large meta-analysis of all the literature, published in 2015, showed that being either overweight or obese increases the risk of liver cancer. This analysis confirms what many other studies have shown in the last few years, including one study looking at 5.2 million people in the UK [10, 59, 60].

 

References

10. Bhaskaran, K. et al. Body-mass index and risk of 22 specific cancers : a population-based cohort study of 5.24 million UK adults. Lancet 6736, 1–11 (2014). View summary on PubMed

58. World Cancer Research Fund & American Institute for Cancer Research. Diet, nutrition, physical activity and liver cancer (2015) View resource

59. Larsson, S. C. & Wolk, A. Overweight, obesity and risk of liver cancer: a meta-analysis of cohort studies. British journal of cancer 97, 1005–8 (2007). View summary on PubMed

60. Chen, Y. et al. Excess body weight and the risk of primary liver cancer: an updated meta-analysis of prospective studies. European journal of cancer (Oxford, England : 1990) 48, 2137–45 (2012). Vew summary on PubMed

The gastric cardia is the part of the stomach that is connected to the oesophagus. Cancer of this part of the stomach has become more common in developed countries, and scientists think that this is closely linked to obesity [39], [43]. This cancer can sometimes be referred to as cancer of the oesophagogastric junction or gastroesophageal junction [44], [45].

As with oesophageal cancer, more than 1 in 5 cases of this cancer may be caused by overweight or obesity, and the risk is higher for those who also smoke [44].

The risk of gastric cardia cancer is nearly doubled in obese people compared to those of a healthy weight [39], [43].

Analyses of studies looking at obesity and gastric cancer have associated excess body weight with an increased risk of gastric cardia cancer [46]–[48]. The most recent analysis of studies on weight and stomach cancer by the World Cancer Research Fund concluded higher BMI is probably a cause of gastric cardia cancer. The report found a 23% increased risk of cardia cancer with each 5kg gain in weight [48].

It is unclear how excess body weight may lead to the development of gastric cardia cancer. Obesity can promote the reflux of acid from the stomach into the oesophagus, which can damage the gastric cardia and make cancer in this part of the stomach more likely [47], [48]. Fat tissue may also change the levels of hormones in the body which can promote cell growth [47]. 

 

References

39. Kubo, A. & Corley, D. A. Body mass index and adenocarcinomas of the esophagus or gastric cardia: a systematic review and meta-analysis. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 15, 872–8 (2006). View summary on PubMed

43. Turati, F., Tramacere, I., La Vecchia, C. & Negri, E. A meta-analysis of body mass index and esophageal and gastric cardia adenocarcinoma. Annals of oncology : official journal of the European Society for Medical Oncology / ESMO 24, 609–17 (2013). View summary on PubMed

44. Olsen, C. M. et al. Population Attributable Fractions of Adenocarcinoma of the Esophagus and Gastroesophageal Junction. Am. J. Epidemiol., vol. 174, no. 5, pp. 582–590 (2011) View resource

45. Monig, S. P. and Holscher. Clinical Classification Systems of Adenocarcinoma of the Esophagogastric Junction. Recent Results Cancer Res. (2010) View resource on PubMed

46. Yang, P.  et al. Overweight, obesity and gastric cancer risk: results from a meta-analysis of cohort studies. Eur. J. Cancer, vol. 45, no. 16, pp. 2867–2873 (2009) View summary on PubMed

47. Chen, Y. et al. Body mass index and risk of gastric cancer: a meta-analysis of a population with more than ten million from 24 prospective studies. Cancer Epidemiol. Biomarkers Prev., no. Ci, pp. 1395–1409 (2013) View summary on PubMed

48. World Cancer Research Fund/American Institute for Cancer Research. Diet, nutrition, physical activity and stomach cancer. (2016) View resource

 

Obesity has been associated with an increased risk of gallbladder cancer [7], [26], [50], [61]–[64]. The most recent analysis of studies looking at weight and gallbladder cancer by the World Cancer Research Fund concluded higher BMI probably causes gallbladder cancer [62]. The report found a 25% increased risk of gallbladder cancer for each 5 unit increase in BMI. 

It is estimated that nearly a fifth of gallbladder cancers result from people being overweight or obese [11], [26]. Compared to men, more than double the number of cases in women seem to be linked to excess body weight [61]. Other studies have also found obesity is more strongly associated with risk of gallbladder cancer among women [7], [26], [50], [61], [64].

Obesity is a known cause of gallstones, which can increase the risk of cancer of the gallbladder [61], [62]. And the hormonal changes that result from having more body fat can also increase the risk of gallbladder cancer [62]. 

References

7. Renehan, A. G., Tyson, M., Egger, M., Heller, R. F. & Zwahlen, M. Body-mass index and incidence of cancer: a systematic review and meta-analysis of prospective observational studies. The Lancet 371, 569–78 (2008). View summary on PubMed

11. Parkin, D. M. & Boyd, L. 8. Cancers attributable to overweight and obesity in the UK in 2010. British journal of cancer 105 Suppl, S34–7 (2011). View summary on PubMed

26. Renehan, A. G. et al. Incident cancer burden attributable to excess body mass index in 30 European countries. International journal of cancer. Journal international du cancer 126, 692–702 (2010). View summary on PubMed

50. World Cancer Research Fund/ American Institute for Cancer Research. Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. 537 (AICR, 2007). View resource

61. Larsson, S. C. & Wolk, A. Obesity and the risk of gallbladder cancer: a meta-analysis. British journal of cancer 96, 1457–61 (2007). View summary on PubMed

62. World Cancer Research Fund & American Institute for Cancer Research. Diet, nutrition, physical activity and gallbladder cancer (2015). View resource

63. Park, M. et al. Body mass index and biliary tract disease: a systematic review and meta-analysis of prospective studies. Prev. Med. (Baltim) (2014) View summary on PubMed

64. Tan, W. et al. Body Mass Index and Risk of Gallbladder Cancer : Systematic Review and Meta-Analysis of Observational Studies. Nutrients, no. Dm, pp. 8321–8334 (2015) View resource

Section currently under review. 

Section currently under review. 

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Section currently under review. 

The way that fat is distributed around the body can also affect the risk of cancer. ‘Apple-shaped’ people who put on weight around their stomach may have higher risks than ‘pear-shaped’ people who put on weight around their hips [50].

Scientists measure belly fat using either waist circumference (the length of tape that goes around your waist) or waist-to-hip ratio (how wide your waist is compared to your hips) [50]. Studies have found that people with larger waists or waist-to-hip ratios have higher risks of breast cancer [76], bowel cancer in men and women [30], [77], kidney cancer [78], and pancreatic cancer [49], [52]. 

References

30. Pischon, T. et al. Body size and risk of colon and rectal cancer in the European Prospective Investigation Into Cancer and Nutrition (EPIC). Journal of the National Cancer Institute 98, 920–31 (2006). View summary on PubMed

49. Aune, D. et al. Body mass index, abdominal fatness and pancreatic cancer risk: a systematic review and non-linear dose-response meta-analysis of prospective studies. Annals of oncology : official journal of the European Society for Medical Oncology / ESMO 23, 843–52 (2012). View summary on PubMed

50. World Cancer Research Fund/ American Institute for Cancer Research. Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. 537 (AICR, 2007). View resource

52. Stolzenberg-Solomon, R. Z. et al. Adiposity, physical activity, and pancreatic cancer in the National Institutes of Health-AARP Diet and Health Cohort. American journal of epidemiology 167, 586–97 (2008). View summary on PubMed

76. Connolly, B. S. et al. A meta-analysis of published literature on waist-to-hip ratio and risk of breast cancer. Nutrition and cancer 44, 127–38 (2002). View summary on PubMed

77. Dai, Z., Xu, Y.-C. & Niu, L. Obesity and colorectal cancer risk: a meta-analysis of cohort studies. World journal of gastroenterology : WJG 13, 4199–206 (2007). View summary on PubMed

78. Luo, J. et al. Body size, weight cycling, and risk of renal cell carcinoma among postmenopausal women: the Women’s Health Initiative (United States). Am. J. Epidemiol., vol. 166, no. 7, pp. 752–9 (2007) View summary on PubMed

Obesity most likely increases the risk of cancer by raising levels of hormones such as oestrogen and insulin [79], [80].

In early life, oestrogen is mainly produced by a woman’s ovaries, but this stops after menopause. Instead, fat in the body becomes the main source of oestrogen. Obese women have up to twice as much oestrogen as women with a healthy weight [81]. They also have lower levels of SHBG, or ‘sex hormone binding globulin’, which mops up oestrogen in the body [79], [82]. This is almost certainly why obesity increases the risk of breast and womb cancers [79], [82]–[84].

Obesity also increases levels of insulin in the body [79]. It’s not clear how this could lead to cancer. One explanation is that if insulin levels are raised for long periods of time, it can affect the number of signalling molecules known as growth factors that are available to cells. Growth factors signal for cells to divide and can enable cancerous cells to survive [85]. High insulin levels are a common feature of many cancers and could explain why being obese increases the risk of liver [60], womb [86], bowel [87], kidney [78] and pancreatic cancer [51].

Obesity may also increase the risk of cancer by causing body tissue to become chronically inflamed. As people gain weight, specialised immune cells spread into the fat tissue causing inflammation. These immune cells release chemicals that tell cells to divide. Obese people tend to have higher levels of these chemicals in their blood [88].

Obesity could also cause cancer through other means, including:

  • increasing the risk of oesophageal and gastric cardia cancers by causing ‘gastric acid reflux’, a condition where the stomach’s acids are briefly pushed back into the throat [89]. This damages the lining of the oesophagus and the area where it connects to the stomach.
  • increasing the risk of gallstones, which in turn increase the risk of gallbladder cancer [61], [62].
  • being associated with physical inactivity or unhealthy diets, both of which are independent risk factors for cancer.

Read more about how researchers think obesity causes cancer on the Cancer Research UK blog

 

References

51. World Cancer Research Fund. Food, nutrition, physical activity and the prevention of pancreatic cancer (2012) View resource

60. Chen, Y. et al. Excess body weight and the risk of primary liver cancer: an updated meta-analysis of prospective studies. European journal of cancer (Oxford, England : 1990) 48, 2137–45 (2012). View summary on PubMed

61. Larsson, S. C. & Wolk, A. Obesity and the risk of gallbladder cancer: a meta-analysis. British journal of cancer 96, 1457–61 (2007). View summary on PubMed

62. World Cancer Research Fund & American Institute for Cancer Research. Diet, nutrition, physical activity and gallbladder cancer (2015). View resource

78. Luo, J. et al. Body size, weight cycling, and risk of renal cell carcinoma among postmenopausal women: the Women’s Health Initiative (United States). American journal of epidemiology 166, 752–9 (2007). View summary on PubMed

79. De Pergola, G. & Silvestris, F. Obesity as a major risk factor for cancer. Journal of obesity 2013, 291546 (2013). View summary on PubMed

80. Louie, S. M., Roberts, L. S. & Nomura, D. K. Mechanisms linking obesity and cancer. Biochimica et biophysica acta 1831, 1499–508 (2013). View summary on PubMed

81. Huang, Z. et al. Dual effects of weight and weight gain on breast cancer risk. JAMA : the journal of the American Medical Association 278, 1407–11 (1997). View summary on PubMed

82. Key, T. J. et al. Body mass index, serum sex hormones, and breast cancer risk in postmenopausal women. Journal of the National Cancer Institute 95, 1218–26 (2003). View summary on PubMed

83. Hankinson, S. E. et al. Plasma sex steroid hormone levels and risk of breast cancer in postmenopausal women. Journal of the National Cancer Institute 90, 1292–9 (1998). View summary on PubMed

84. Kaaks, R., Lukanova, A. & Kurzer, M. S. Obesity, endogenous hormones, and endometrial cancer risk: a synthetic review. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 11, 1531–43 (2002). View summary on PubMed

85. Pollak, M. Insulin and insulin-like growth factor signalling in neoplasia. Nature Reviews Cancer. vol. 8 (2008) View summary on PubMed 

86. Wang, T. et al. A prospective study of inflammation markers and endometrial cancer risk in postmenopausal hormone nonusers. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 20, 971–7 (2011). View summary on PubMed

87. Jenab, M. et al. Serum C-peptide, IGFBP-1 and IGFBP-2 and risk of colon and rectal cancers in the European Prospective Investigation into Cancer and Nutrition. International journal of cancer. Journal international du cancer 121, 368–76 (2007). View summary on PubMed 

88. Park, J. et al. Obesity and cancer-mechanisms underlying tumour progression and recurrence. Nat. Rev. Endocrinol. vol. 10, no. 8, pp. 455–465 (2014) View summary on PubMed

89. Freeman, H. J. Risk of gastrointestinal malignancies and mechanisms of cancer development with obesity and its treatment. Best Pract. Res. Clin. Gastroenterol. vol. 18, no. 6, pp. 1167–75 (2004) View summary on PubMed

 

Studies have shown that overweight and obese people are more likely to develop cancer than people with a healthy body weight [79], [90]. It therefore makes sense that losing weight can help to reduce the risk of cancer. It is difficult to design studies to confirm this, but some large studies have found that losing weight can help reduce the risk [91]–[95].

One study found that women who lost 20 pounds or more had 11% lower risks of cancer overall compared to women who had never lost that much weight [92].  Another study found that women who lost 10kg since menopause, and kept the weight off, more than halved their risk of breast cancer [96]. Other studies have found similar results for breast and other types of cancer [94], [95].

A review of many studies found that, overall, the risk of cancer is lower for people that intentionally lose weight, compared to those who don’t [97].

When people try to lose weight through short-term fixes, in most cases, they end up putting the weight back on [98]. It’s unclear how this ‘weight cycling’ affects the risk of cancer.

One study found that women whose weight had gone up and down by over 10 pounds, more than ten times, had higher risks of kidney cancer than those whose weight was stable [78]. Another study found that in women that had ever had a BMI of 30 or higher, those that lost and gained 9 kg or more at least once were nearly three times more likely to develop womb cancer [99]. And there are indications that it may also increase the risk of non-Hodgkin’s lymphoma [98].

An analysis of studies looking at adult weight change and risk of colorectal cancer found a 3% increased risk of the disease with each 5kg gain in weight [32]. The analysis didn’t find an association between weight loss and cancer risk.     

Other research has found the opposite. A large study in the US looking at weight cycling and the risk of cancer found purposely losing and then regaining 10 pounds (4.54kg) was not associated with an increased risk of cancer when BMI was taken into account [100]. However this study didn’t take into account when during adulthood the people lost and gained weight, nor whether they lost or gained more than 10 pounds.

More studies looking into the effect of losing and gaining weight on cancer risk are needed before we can be certain of a link. But while weight cycling is a new area of research and only a few types of cancer have been studied, it does suggest that the best way to reduce the risk of cancer is to maintain a healthy bodyweight over time. 

References

32. Karahalios, A., English, D. R. and Simpson, J. A. Weight change and risk of colorectal cancer: a systematic review and meta-analysis. Am. J. Epidemiol., vol. 181, no. 11, pp. 832–845 (2015) View summary on PubMed

78. Luo, J. et al. Body size, weight cycling, and risk of renal cell carcinoma among postmenopausal women: the Women’s Health Initiative (United States). American journal of epidemiology 166, 752–9 (2007). View summary on PubMed

79. De Pergola, G. & Silvestris, F. Obesity as a major risk factor for cancer. Journal of obesity 2013, 291546 (2013). View summary on PubMed

90. Louie, S. M., Roberts, L. S. & Nomura, D. K. Mechanisms linking obesity and cancer. Biochimica et biophysica acta 1831, 1499–508 (2013). View summary on PubMed

91. Sjöström, L. et al. Effects of bariatric surgery on cancer incidence in obese patients in Sweden (Swedish Obese Subjects Study): a prospective, controlled intervention trial. The Lancet Oncology 10, 653–62 (2009). View summary on PubMed

92. Parker, E. D. & Folsom, A. R. Intentional weight loss and incidence of obesity-related cancers: the Iowa Women’s Health Study. International journal of obesity and related metabolic disorders : journal of the International Association for the Study of Obesity 27, 1447–52 (2003). View summary on PubMed

93. Harvie, M. et al. Association of gain and loss of weight before and after menopause with risk of postmenopausal breast cancer in the Iowa women’s health study. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 14, 656–61 (2005). View summary on PubMed

94. Eng, S. M. et al. Body size changes in relation to postmenopausal breast cancer among women on Long Island, New York. American journal of epidemiology 162, 229–37 (2005). View summary on PubMed

95. Rodriguez, C. et al. Body mass index, weight change, and risk of prostate cancer in the Cancer Prevention Study II Nutrition Cohort. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 16, 63–9 (2007). View summary on PubMed

96. Harvie, M. et al. Association of Gain and Loss of Weight before and after Menopause with Risk of Postmenopausal Breast Cancer in the Iowa Women’s Health Study. Cancer Epidemiol. Biomarkers Prev., vol. 14 (2005). View summary on PubMed

97. Birks, S., Peeters, A., Backholer, K., O’Brien, P. & Brown, W. A systematic review of the impact of weight loss on cancer incidence and mortality. Obesity reviews : an official journal of the International Association for the Study of Obesity 13, 868–91 (2012). View summary on PubMed

98. Thompson, H. J. & McTiernan, A. Weight cycling and cancer: weighing the evidence of intermittent caloric restriction and cancer risk. Cancer prevention research (Philadelphia, Pa.) 4, 1736–42 (2011). View summary on PubMed

99. Nagle, C. M. et al. Impact of weight change and weight cycling on risk of different subtypes of endometrial cancer. European journal of cancer (Oxford, England : 1990) 49, 2717–26 (2013). View summary on PubMed

100.  Stevens, V. L. et al. Weight cycling and cancer incidence in a large prospective US cohort. Am. J. Epidemiol., vol. 184 (1) (2015). View resource

Eating habits established in childhood often endure after many years. In 1993, a group of scientists showed that at least half of obese children were still obese as adults [101]. Another study found infants under the age of two who were obese were predisposed to obesity later in life [102]. And a more recent study in Finland recorded children’s weight or BMI at 5 months, 1 year, ages 2-5, and finally at age 31 [103]. They found that children with the highest BMI from the age of 3 were over three times more likely to be obese as adults.

A recent analysis that brought together the results of 15 previous studies confirmed that obese children and teenagers were around five times more likely to be obese as adults [42]. It also suggested teenage weight might be an even stronger predictor of adult obesity than childhood obesity, because some children shed their excess fat during puberty.

A study of Scottish and English children found that people who are obese as children have higher risks of some cancers later on in life [104]. Excess weight in childhood may increase the risk of cancer later on in life by making it more likely that the child will be obese as an adult. There is a possibility that childhood obesity could directly increase a child’s risk of cancer as an adult, regardless of what he or she grows up to weigh, but the evidence is uncertain. We discuss this evidence on the Cancer Research UK blog.

 

References 

42. Simmonds, M. et al. Predicting adult obesity from childhood obesity: a systematic review and meta-analysis. Obesity Reviews (2016). View summary on PubMed

101. Serdula, M. K. et al. Do obese children become obese adults? A review of the literature. Preventive medicine 22, 167–77 (1993). View summary on PubMed

102. Baird, J. et al. Being big or growing fast: systematic review of size and growth in infancy and later obesity. BMJ pp. 4–9, (2010) View resource

103. Graversen, L. et al. Preschool weight and body mass index in relation to central obesity and metabolic syndrome in adulthood. PloS one 9, e89986 (2014). View summary on PubMed

104. Jeffreys, M. et al. Childhood body mass index and later cancer risk: a 50-year follow-up of the Boyd Orr study. International journal of cancer. Journal international du cancer 112, 348–51 (2004). View summary on PubMed

 

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