Sensex fell by over hundred points at mid-session today, on profit booking and reports of a sharp rise in food inflation.Spiked by the news, the Sensex that had commenced the day with gains of 125 points, fell by 113 points to 20,189 level. The broad-based National Stock Exchange index Nifty also lost 31.30 points at 6,049 level, after trading 36.35 points higher in the opening trade.