Your colon is meant to push undigested food - waste - out and allow the body to absorb healthy nutrients and minerals. Processed foods and foods with little fiber are slow movers in the colon and tend to block the colon like a slow car in front of the fast cars - foods high in fiber are the fast cars. This way some "buildup of waste" can occur. On average, a colon can contain 6-8 meals before pushing it out. Not eliminating waste but building it up is unhealthy and may cause occasional constipation, bloating, and feelings of being low in energy.