A study by the Journal of the National Cancer Institute (JNCI) discusses the relationship between TV viewing time, recreational sitting time, occupational sitting time, and total sitting time with the risk of various cancers. The study was a meta-analysis of dozens of sedentary behavior research studies. When the highest levels of sedentary behavior were compared to the lowest, a statistically significant higher risk was found for three particular types of cancer: lung, colon and endometrial.
The researchers noted that sedentary behavior had a detrimental impact on cancer even among physically active people, which reinforces other studies that have said that focused workouts, alone, are not enough to ward off the negative effects of prolonged sitting.
Full article can be found here: http://medicalxpress.com/news/2014-06-sedentary-behavior-cancers.html