The effects of not exercising include increased risk of heart disease, diabetes, cancer and obesity, according to WebMD. An overly sedentary lifestyle also is a risk-factor for anxiety, deep vein thrombosis, depression, colon cancer, high blood pressure, osteoporosis, lipid disorder, kidney stones, immune system dysfunction and muscle atrophy, notes Wikipedia. Many people are sedentary to the point they are considered to have sitting disease, explains WebMD.
Sitting disease is a condition where a person spends most of his time sitting, such as at a sedentary office job, explains WebMD. This leads to too much "screen time," which is time spent in front of a computer, television or mobile device. An overabundance of screen time has been linked to health problems, according to Wikipedia.
Wikipedia also notes that health risks are especially high in those that sit for more than five hours per day. Those who sit for long periods but also exercise more than four hours per week have been shown to remain healthy.
WedMD cites James Levine, M.D., author of "Move a Little, Lose a Lot," as stating that it's strange that so many people are now spending all day in a chair. He considers this a form of physical entrapment. He believes that the human body needs exercise in order to remain healthy.