You could also look at the reverse of this from reading several of the posts above. Maybe power lifting causes one to gain more body fat as a side affect to gaining the muscle mass. There is a big difference in the way you feel while toning than lifting for sheer power. To put that kind weight into motion takes more fuel and more substancial fuel like protien which is often accompanied by hidden sources of fat. I have gained on the bench while losing weight but I found the more I focused of the lifting, the more it got the fuel it demanded. I'm a big lad at 245 lbs and my bench is at 370 for 12 reps. I've been at it for about 18 months after a long period away. I've gained 10 pounds in that time frame. My point is that fat doesn't add to strength. Added strength causes the addition of weight.