Well... frankly, if your already tubby and uncomfortable in your own skin and jeans forget IWB for awhile.
If your thin or atleast somewhat comfortable go ahead with IWB so long as your pants arent painted on already, otherwise prepare to buy the next waist size up.
I'm right on the border - 6' and 230, and I notice every millimeter of belly or lovehandle conspiring to push my belt down further along with the gun.
I'd suggest starting with a small light gun - little Ruger LCP for your first IWB in a Bearcreek holster with a nice forward cant is a great first carry package.
Its thin and easy to stuff into your existing waistband, its light weight, its smooth, its rounded off with a angled rear slide area (doesnt have a pointy corner) and its just downright easy to carry right from the start even if your britches are a bit snug.
In a week or two, no matter how pissy it makes you feel the first day or three, you will quickly get used to it and after 2 months you'll be totally sold on IWB and forget all about pocket carry, shoulder carry, armpit carry, buttcra... you get the point.
Lasty, you can completely forget attempting to stuff some 1911, Block, 92FS, or ANY other full-size or double stack "compact" into your waist until youve spent some time with a smaller gun in there already.
Fact is... this CC business is u-n-c-o-m-f-o-r-t-a-b-l-e.
Starting with a big gun will end your ccw life before you get out the door.