Hey uhh, what u need to do, is just be more active, ride ur bike in ur free time, walk down town. I think that yes u could start with 10 situps each night but how bout evry week u add 10 more? And try doing some sit-ups. But it doesn't mean u'll be tiny in no time, 147 isn't really too bad. If u gained like 10 lbs then maybe u could try like a diet, but ya know wut? It doesn't matter because u may be healthy anyways. You might just have a little extra skin.