Background: Graduated HS in '07. Ran in the low 18's for cross. 40-50mpw in offseasons. 6'4" and 170lbs when I graduated. Looking back, I can see that I was most definitely malnourished, as I was a fast growing very active male that was probably only eating, at the most, 2000 calories a day.
Fast forward to 2016. I'm 28 years old, 6'4", and 215lbs. I've run myself down from 235 and I feel a million times better. I've lifted weights since college, so I've got a little muscle hiding under the flab. But I've been increasing my mileage over the last couple of months, hoping I would see some improvements after the weight came off, but I'm still running reeeaaaaallllllllyyyy slow. An easy jog for me is around 10min/mile, and I start breathing pretty heavy if, say, I run 5 miles at 9:00/mile pace.
(if it makes any difference, the dew point has rarely dropped under 70 since I started training)
So my question is, how much slower am I because of the additional weight? If I lost 10-15lbs and kept the same mileage (20-30mpw), would I see big improvements? I want to really get back into the sport and have some fun with it, but it's been a real rough couple months back.