We used to do the Ranger 5 mile standard run a lot. This guy had a pot belly and didn't look in shape at all. But he would max his PT test and smoke the 5 mile run under 7 min miles every time.
He would leave me in the dust. Nobody believed that he could score so high on the PT events because he was fat. He wasn't the only one I encountered during my 20 years in the Army or 25 total years of doing crazy cardio everyday.
I trained alongside many guys who didn't look in shape but they could do amazing things. Endstate: Performance and body composition do not correlate and one doesn't necessarily impact the other, the way traditionalists claim.
Make sure you know why you are running. If you run because you are an athlete or soldier, then train accordingly. If you run because you like it, then enjoy yourself and do whatever makes you happy. But if you run because you are trying to lose weight or for body composition, then you need to do it right.
Couch to 5k programs, 5k's, 10k's, mud runs, half marathons and marathons have nothing to do with getting lean and are not efficient for that at all. Those programs are designed for nothing other than to get you to complete a distance for time.
Train for the task at hand and don't try to swim in a bathtub for open ocean swims.
If you want to learn effective training techniques for performance or body composition, let me know and I can show you how to train effectively and efficiently for your specific goals.