Why am i losing more weight now that i have gone off my diet?

for the previous 2 weeks i was eating mostly fruit, vegetables and protein bars. i was loosing some weight but not that much body fat(i have an electronic body composition scale). latly i have began eating a modified normal diet and i am loosing a lot more body fat and gaining muscle, while maintaining the same weight. i still don't overeat or eat completely unhealthy, but i do eat junkfood- junkfood containing all natural ingredients(imported nestle from europe). why am i loosing so much body fat? i do run at least 3 miles a day and do as much pull ups and chinups as i can.