The body of evidence is strong that physical inactivity and obesity (BMI > 30kg/m2) are independent risk factors for many non-communicable diseases, including some cancers (especially breast and colorectal), and are associated with greater rates of all-cause mortality1.
Ekelund et al.2 recently published a paper reporting a 12 year follow up of participants in the EPIC study, a large European prospective cohort study (n= 334,161). Population attributable fraction (PAF) were calculated, which estimate the proportion of new cases of a disease that would not happen if the risk factor were absent. They found that if all inactive participants increased their activity levels (by a modest amount) all-cause mortality would reduce by 7.35%.
This compared to PAF for avoiding high waist circumference (> 88cm in women; ≥ 102cm in men) of 6.53% and for avoiding obesity of 3.66%. These results suggest that the combined action to reduce inactivity, waist circumference and body weight obesity might offer greatest health benefits.
1 Lee IM, Lobelo F, Puska P et al. (2012) Effect of physical inactivity on major non-communicable diseases worldwide: an analysis of burden of disease and life expectancy. The Lancet;382:219-229
2 Ekelund U, Ward HA, Norat T et al. (2015) Physical inactivity and all-cause mortality across levels of overall and abdominal adiposity in European men and women: the European Prospective Investigation into Cancer and Nutrition Study (EPIC) Am J Clin Nutr;101:613-21