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Body weight

Body weight and cancer: the evidence

Evidence linking bodyweight to cancer.

This page contains information about the links between bodyweight and cancer. Click on the links below to read about specific topics.

You can find out more about the evidence behind other health topics in our other How do we know? pages.

Obesity is a major preventable cause of cancer

Major studies confirm that being overweight or obese increases your risk of various cancers.1 2 3 4 The World Health Organisation (WHO) says that overweight and obesity are the most important known avoidable causes of cancer after tobacco.5

In the UK, about 13,000 people every year could avoid getting cancer if they maintained a healthy body weight.6 This number is only going to increase in the future since more cancers are being linked to obesity, and the number of people who are overweight is increasing.

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Obesity increases the risk of breast cancer in women after menopause

Scientists have estimated that anywhere between 7% and 15% of breast cancer cases in developed countries are caused by obesity.7 8 9 Over a hundred studies show that women who are overweight or obese and have been through the menopause have higher breast cancer risks.3 10

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.4 10 This means that if the average lifetime risk of breast cancer is one in nine, an obese woman’s lifetime risk is one in seven.

Obesity does not increase the risk of breast cancer in women before their menopause.11 12 However, women who are overweight or obese at this point in their lives often find it hard to lose weight after their menopause.

Putting on weight over time can also increase the risk of breast cancer. Studies have found that after the age of 18:

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Obesity increases the risk of bowel cancer

Obesity is one of the most important causes of bowel cancer.2 5 Some groups have estimated that obesity causes about 11-14% of bowel cancer cases.7 9

Many large studies have found that bowel cancer is more common in overweight or obese people.3 14 15 16 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.15 16

When BMI is used to measure body fat, studies tend to find that only obese men have a higher risk of bowel cancer. But when researchers use waist circumferences or waist-to-hip ratios, both obese men and women have higher risks of bowel cancer.16 This suggests that for women at least, fat around the stomach is more of a problem than fat elsewhere on the body.17

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Obesity increases the risk of womb cancer

A large body weight is one of the most important causes of womb cancer. A study of one million women estimated that up to half of all cases of womb cancer in the UK are caused by being overweight or obese.4

Studies have consistently found that obese people are three to four times more likely to develop womb cancer than people with a healthy bodyweight.4 18 19

Obesity increases the risk of oesophageal cancer

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

Being overweight doubles the risk of developing this cancer,20 and being obese can triple the risk.1 21 Experts have estimated that in Western countries, it causes about 37% of this type of cancer.9 In fact, the rates of oesophageal adenocarcinoma in white UK men are among the highest in the world and rising. Some studies have suggested that this type of cancer may be becoming more common because of rising levels of obesity.20 21

Obesity increases risk of many other types of cancer

Studies have consistently found that people who are overweight or obese are also more likely to develop pancreatic,22 23 kidney,24 and gallbladder cancers.25 Studies have estimated that having a high body weight accounts for a quarter of kidney and gallbladder cancers.6

And there is more and more evidence that being overweight or obese could increase the risk of many other types of cancer, including:

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Too much belly fat could increase the risk of cancer

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.

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). Studies have found that people with larger waists or waist-to-hip ratios have higher risks of breast cancer,34 bowel cancer,17 kidney cancer,35 and pancreatic cancer.22

Obesity may increase cancer risk by changing hormone levels

Obesity most likely increases the risk of cancer by raising levels of hormones such as oestrogen and insulin.

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 and obese women have up to twice as much oestrogen as women with a healthy weight.36 They also have lower levels of SHBG, or ‘sex hormone binding globulin’, which mops up oestrogen in the body 37. This is almost certainly why obesity increases the risk of breast and womb cancers.37 38 39

Obesity also increases levels of insulin in the body. It’s not clear how this could lead to cancer, although high insulin levels are a common feature of many cancers. High insulin levels could explain why being obese increases the risk of bowel, kidney and pancreatic cancer.40 41 42

Obesity could also cause cancer through other means, including:

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Keeping a healthy weight reduces cancer risk and losing weight may reduce cancer risk

Studies have shown that overweight and obese people are more likely to develop cancer than people with a healthy body weight. It therefore makes sense that losing weight can help to reduce the risk of cancer, and scientists are now trying to confirm this with large studies.44 45 46 47

One study found that women who lost 20 pounds of more had 11% lower risks of cancer overall compared to women who had never lost that much weight.48 Another study found that women who lost 10kg since menopause and kept the weight off more than halved their risk of breast cancer.45 Other studies have found similar results for breast and other types of cancer

When people try lose weight through short-term fixes, in most cases, the end up putting the weight back on. It’s unclear how this ‘weight cycling’ affects the risk of cancer. But at least 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.35 While this was just a single study, it does suggest that the best way to reduce the risk of cancer is to maintain a healthy bodyweight over time.

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Parents can reduce their children’s cancer risk in adult life by encouraging them to eat healthily and keep active

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 49. And this proportion is likely to be even higher now. Another study of Scottish and English children found that people who are obese as children have higher risks of some cancers later on in life 50.

Many studies have shown that children with obese parents are much more likely to be obese themselves 51. But this may not be due to parenting styles. Some research from Cancer Research UK indicates children’s attitudes towards food may be due to genes. By inheriting certain genes from their parents, some children may have a higher chance of being overweight or obese 52.

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References

  1. Bianchini, F., R. Kaaks, and H. Vainio, Overweight, obesity, and cancer risk. Lancet Oncol, 2002. 3(9): p. 565-74.PubMed
  2. IARC, Weight Control and Physical Activity. IARC Handbooks of Cancer Prevention, ed. H. Vainio and F. Bianchini. Vol. 6. 2002, Lyon: IARC.
  3. Renehan, A.G., et al., Body-mass index and incidence of cancer: a systematic review and meta-analysis of prospective observational studies. Lancet 2008. 371(569-578).PubMed
  4. Reeves, G.K., et al., Cancer incidence and mortality in relation to body mass index in the Million Women Study: cohort study. Bmj, 2007.PubMed
  5. WHO/FAO, Joint WHO/FAO Expert Consultation on Diet, Nutrition and the Prevention of Chronic Diseases, in WHO Technical Report Series. 2003, WHO: Geneva. p. 95-104.Link
  6. Bergstrom, A., et al., Overweight as an avoidable cause of cancer in Europe. Int J Cancer, 2001. 91: p. 421-430.PubMed
  7. Danaei, G., et al., Causes of cancer in the world: comparative risk assessment of nine behavioural and environmental risk factors. Lancet, 2005. 366(9499): p. 1784-93.PubMed
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  21. Merry, A.H., et al., Body Mass Index, height and risk of adenocarcinoma of the oesophagus and gastric cardia: a prospective cohort study. Gut, 2007.PubMed
  22. Berrington de Gonzalez, A., et al., Anthropometry, Physical Activity, and the Risk of Pancreatic Cancer in the European Prospective Investigation into Cancer and Nutrition. Cancer Epidemiol Biomarkers Prev, 2006. 15(5): p. 879-885.PubMed
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  25. Larsson, S.C. and A. Wolk, Obesity and the risk of gallbladder cancer: a meta-analysis. Br J Cancer, 2007.PubMed
  26. Benson, V.S., et al., Lifestyle factors and primary glioma and meningioma tumours in the Million Women Study cohort. Br J Cancer, 2008. 99(1): p. 185-90.PubMed
  27. Engeland, A., et al., Height and body mass index and risk of lymphohematopoietic malignancies in two million Norwegian men and women. Am J Epidemiol, 2007. 165(1): p. 44-52.PubMed
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  30. Larsson, S.C. and A. Wolk, Obesity and risk of non-Hodgkin's lymphoma: A meta-analysis. Int J Cancer, 2007.PubMed
  31. Schouten, L.J., et al., Height, body mass index, and ovarian cancer: a pooled analysis of 12 cohort studies. Cancer Epidemiol Biomarkers Prev, 2008. 17(4): p. 902-12.PubMed
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  40. Otani, T., et al., Plasma C-peptide, insulin-like growth factor-I, insulin-like growth factor binding proteins and risk of colorectal cancer in a nested case-control study: The Japan public health center-based prospective study. Int J Cancer, 2007.PubMed
  41. 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. Int J Cancer, 2007.PubMed
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  46. Eng, S.M., et al., Body Size Changes in Relation to Postmenopausal Breast Cancer among Women on Long Island, New York. Am J Epidemiol, 2005.PubMed
  47. Rodriguez, C., et al., Body Mass Index, Weight Change, and Risk of Prostate Cancer in the Cancer Prevention Study II Nutrition Cohort. Cancer Epidemiol Biomarkers Prev, 2006.PubMed
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  49. Serdula, M., et al., Do obese children become obese adults? A review of the literature. Prev Med, 1993. 22: p. 167-77.PubMed
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Page last updated: 01 August 2008
 
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