erm, really not too clued up on this but i'd guess at making sure you include some short burst runs, and/or take a skipping rope for when your dad is cooling down - 10 minutes skipping = 1 hour jogging in my experience. Mix it with some slow crunches - just cos if your belly feels 'tigher' it makes you feel like your making progress and spurs you on. Make sure you eat less calories than your burning and it should just happen.