Quite the opposite for me. I exercise 4-5 days per week. I'm coming up to my last 1.5 stones and find the exercise keeps the weight losses constant at 3-5lbs per week rather than plateau. The bulk of my routine is made up of cardio - treadmill, rower, spinning. But I also do squats, light weights and plenty of stomach exercises. It was hard in the beginning but I find I have more energy now and can word harder. Even if the exercise isn't actually assisting the weight loss, it certainly helps tone.