UICC World Cancer Congress 2006

In the last two decades obesity and related metabolic consequences have been recognized as contributory risk factors for some types of cancers. Thus, obesity prevention is increasingly recognized as an important factor in cancer control.

It is estimated that around one third (188,277) of all (564,830) US cancer deaths likely to occur in 2006 will be related to poor nutrition, physical inactivity, overweight and obesity1. Within the European Union about 5% (3% in men, 6% in women) of all incident cancers might be prevented if BMI was maintained below 25 kg/m2 2 . Globally, the WHO International Agency for Research on Cancer estimate that overweight and inactivity account for a quarter to a third of cancers of the breast, colon, endometrium, kidney, and oesophagus3. It is also clear that physically active men and women have about a 30- 40% reduction in the risk of developing colon cancer, whilst physically active women have a 20-30% reduction in breast cancer risk compared with inactive women4. In addition to total body weight, the distribution of fat storage also provides an indicator of cancer risk with higher waist circumference associated with a two fold risk of colon cancer5. Current recommendations for cancer prevention highlight the need to avoid being underweight or overweight and to limit weight gain during adulthood to less than 5 kg (11 pounds) 6

The mechanisms involved in the relationship between weight gain and the development of cancer have been the focus of considerable research and concentrate largely on the hormonal/metabolic responses related to energy balance3. The latter are associated with the metabolic syndrome and the inflammatory mediators linked to increase adipose tissue. Paradoxically, whilst scientific understanding of the relationship between obesity and the development of cancer increases rapidly, our understanding and ability of how to impact effectively on human behaviors (e.g. over consumption and under activity) remains low.

According to WHO, obesity is increasing worldwide at an alarming rate, in both developed and developing countries. For example, US trends in obesity show that between 1999 and 2004, there was an increase in the prevalence of overweight in girls (13.8% to 16.0%) , boys (14.0% to 18.2%) and men (27.5% to 31.1%), with no change in women7.

Delaying and preventing the accelerating rates of energy imbalance, improving physical activity and nutrient density will require a range of sustainable interventions which can be easily accessed by all sub–groups in the population. Epidemiological evidence points to the need for a life course approach to weight control and cancer prevention, starting before pregnancy and continuing into older years8. For this to be achieved integrated action is required at individual, community and legislative levels to facilitate and assist populations to achieve small changes in energy intake and energy expenditure.

A small evidence base is now emerging on successful obesity prevention interventions in children through family based approaches, some (but not all) multi-component school based and single component (e.g. focus on soft drinks) programmes, work site activities and community based interventions. It is clear that both diet and physical activity require to be included to address the obesity problem and that the effects of such programmes are relatively short lived. Following the model of tobacco control, these results suggest a much wider environmental approach to obesity prevention is key to facilitating clinincally relevant diet and activity choices, cultural acceptance is required for appropriate actions and that prevention programmes can complement individual efforts to avoid weight gain9.

1American Cancer Society (2006) Early prevention and early detection facts and figures 2006 http://www.cancer.org/docroot/stt/stt_0.asp (accessed 13/04/06)

2Bergström A, Pisani P, Tenet V, Wolk A, Adami H. Overweight as an avoidable cause of cancer in Europe. Int J Cancer 2001;91:421-30

3 WHO (2002) IARC Handbooks of cancer prevention Vol 6 Weight control and Physical activity. IARC Press Lyon

4 Lee-Im (2003) Physical Activity and cancer prevention Med Sci Sports Exerc. 35(11):1823-7.

5 Moore LL et al (2004) BMI and waist circumference as predictors of lifetime colon cancer risk in Framingham Study adults Int J Obes Relat Metab Disord. 28(4):559-67.

6 World Cancer Research Fund & American Institute for Cancer Research Appendix (1997): Food, Nutrition and the Prevention of cancer: A Global Perspective. Washington DC, WCRF , London http://www.wcrf-uk.org/report/summary.lasso (accessed 13/04/06)

7 Ogden CL et al (2006) Prevalence of overweight and obesity in the United States, 1999-2004. JAMA ;295(13):1549-55

8 Uauy R & Solomons N (2005) Diet, nutrition, and the life-course approach to cancer prevention. J Nutr. 135(12 Suppl):2934S-2945S. Review.

9 UICC (2004) Evidence based cancer prevention http://www.uicc.org/index.php?id=976 (accessed 13/04/06)