I started running at over 300 pounds (BMI over 45). What I considered a run then was about 10 - 15 seconds running at a 4.1mph, then walking for 5 minutes at 3.3mph. Now at 220 (BMI 33.1), I run 3 miles in just under 35 minutes on an average day. My last long run was 7 miles in 1h25m, I took 2-3minute walking breaks , ran for the rest (between 4.6-5.2mph).

I ran 5 miles in 58 minutes at a trail race today. My BMI is 32.

What I would say is to set your own goals and keep going even if progress is slow, listen to your body, and you can achieve a lot.