we need some details. Weight, height? Age?
From my experience
1st you need to lose some of that er 'weight'?
2. After you drop the 40 lbs load up on the miles. Start with 15mpw, then work your way up to 100mpw. But take at least 1 day off a week.
3. You are probably a weakling as well so lift weights 3 times a week.
4. And you are probs very slow too no doubt. Do some strides or build ups or diagonals at least 2 times a week. Start with a jog and build up to a full jog, i mean sprint.
5. Next do some hills, I think 2 days a week maybe 100m hills?
6. If you are lazy as I suspect watch some Goggins videos on youtube you need the come to jesus talk.
Oh and Every 4th week take 3 days off to recover.
Do this plan for 2 years then report back to the forum.