The impact of changing the prevalence of overweight/obesity and physical inactivity in Australia: An estimate of the proportion of potentially avoidable cancers 2013-2037.

Globally, 39% of the world's adult population is overweight or obese and 23% is insufficiently active. These percentages are even larger in high-income countries with 58% overweight/obese and 33% insufficiently active. Fourteen cancer types have been declared by the World Cancer Research Fund to be causally associated with being overweight or obese: oesophageal adenocarcinoma, stomach cardia, colon, rectum, liver, gallbladder, pancreas, breast, endometrium, ovary, advanced/fatal prostate, kidney, thyroid and multiple myeloma. Colon, postmenopausal breast and endometrial cancers have also been judged causally associated with physical inactivity. We aimed to quantify the proportion of cancer cases that would be potentially avoidable in Australia if the prevalence of overweight/obesity and physical inactivity in the population could be reduced. We used the simulation modelling software PREVENT 3.01 to calculate the proportion of avoidable cancers over a 25-year period under different theoretical intervention scenarios that change the prevalence of overweight/obesity and physical inactivity in the population. Between 2013 and 2037, 10-13% of overweight/obesity-related cancers in men and 7-11% in women could be avoided if overweight and obesity were eliminated in the Australian population. If everyone in the population met the Australian physical activity guidelines for cancer prevention (i.e. engaged in at least 300 min of moderate-intensity physical activity per week), an estimated 2-3% of physical inactivity-related cancers could be prevented in men (colon cancer) and 1-2% in women (colon, breast and endometrial cancers). This would translate to the prevention of up to 190,500 overweight/obesity-related cancers and 19,200 inactivity-related cancers over 25 years.