Sitting too long and not moving enough makes the body get less physical activity, even when a person actually has time to exercise several times a week. High sedentary habits are associated with various health risks, including metabolic problems, cardiovascular disease, and physical decline. Of course, the effect won't be the same on everyone, but the more time spent without moving, the more important it is to look for opportunities to move between activities.
The solution doesn't always have to be going to the gym or doing strenuous exercise. Standing periodically, taking short walks, using the stairs when possible, doing housework, or taking breaks from sitting for long periods can also help increase daily activity. If your job requires sitting for long hours, try making a simple habit of moving every once in a while. The body is designed to move, not sit in the same position all day.