[ImJustAnotherOkie]

Weight training 3 days a week 45 mins each session will do wonders.

You need good equipment for the range of motion.

[LouAvul]

He's 73 and likely his body will not tolerate that much. At that age he's likely already got arthritis which is exacerbated by strenuous exercise.

Calorie control is key.

Thing is, it's only sensible to find balance. Balance between enjoyable and healthy, because the two aren't always compatible. That's in diet and in exercise.