I am 40 years old. I have taken up running. I started over a year ago. I lost weight at first. I am fairly happy with the shape I am in, except for the belly fat. It won't go away. I run 5 miles about 4 times a week (sometimes 5 times a week). I do not overeat at all. I also do ab work almost everyday. I know people who run less and eat more and have no belly. What is the problem? I would really appreciate any input you may have.