Fat mans arms.

I am just getting going in Blender and have made my first character. I have him doing a basic walk cycle but being that he is rather fat his arm cut through his body as he walks! Is there a fairly easy (new-be) way to get the arms to interact with his body?
Thanks for any help.

softbody modifier might work.
(edit) also check out corrective shape keys, which I think is an add-on. I must warn you though, these things are not necessarily simple.

If you want to animate a fat man walking actually look at a real fat man walking and see what he does with his arms. If in your animation the arms are going through his body then you have failed this basic requirement of learning animation.

Character with large waist tends to walk with there arm swinging out around the body: