What I like about this program is small goals every week.When I started I choose very small pace for both walk and run. I was so afraid of failing....After week 5 I was sure that I can finish the program and at the end of the week 7 I started making 5k distance every time. Now it is week 8 and I slowly increasing my pace.
I am 55, obese (BMI 32.2), high blood pressure and sugar, back pain and other stuff. So the program is doable even for me.
Stick to the program, but listen to your body (and ignore your mind ). If you cannot run - walk. it is better then sitting.