The prevalence of overweight and obesity has increased markedly over the past two decades and has reached global epidemic proportions worldwide. According to World Health Organization estimates in 2008, more than 1.4 billion adults worldwide, 20 years or older, were overweight (BMI ≥ 25) and more than 500 million were obese (BMI ≥ 30). The percentage of Norwegians being overweight has increased by 7% during the last 10 years, and in 2008, 1 in 4 Norwegians was overweight.
Obesity or increased weight is associated with the risk of type-2 diabetes, cardiovascular disease and risk of various cancers. The observational data during the last 25 years show that obesity causes approximately 14% of cancer deaths in men, and up to 20% of cancer deaths in women. The magnitude of this effect is huge, in large part because obesity and diabetes are now so common, and it seems that cancer loves the metabolic environment of the obese person. In Norway alone, 35% of deaths were caused by tumour-related diseases in 2010. Although few data exist on the association of weight gain or weight loss on altering the risk of cancer, evidence suggest that increase in weight during adulthood is associated with increased risk of cancer. In contrary, weight loss over the years may be associated with a reduced risk of cancer incidence. The best evidence in this regard comes from the bariatric surgery studies that suggest a decreased risk of cancer incidence and death associated with a large weight loss after the surgery. Therefore, assessment of the relationship between changes in weight or obesity status over time with the risk of cancer development has clinical implications for general public health perspective, and the advice given to people to modify body weight.
Various strategies have been proposed and implemented to control the obesity pandemic, including healthier choice of food and regular physical exercise. The role of aerobic fitness in the prevention of obesity related cardiovascular disease is well-established. Similarly, observational data show that high levels of fitness are associated with decreased cancer mortality risk, independent of obesity status. Overweight or obese fit individuals had lower risk of cancer deaths compared with unfit counterparts, and it seems that high levels of aerobic fitness and physical activity modify the association of obesity-related cancers. The prevention and control of overweight and obesity through life-style changes, i.e., healthy eating, engage in more physical activity have substantial benefits to reduce the obesity-related cancer risk.
Written by Javaid Nauman, Post Doc CERG, NTNU.