The Effect: You'll look better in your clothes.
Bigger guys often make the mistake of either buying clothes too big thinking it'll make them look smaller. No, you shouldn't have to squeeze in to a smaller size, just wear what actually fits you. The shoulder stitches should sit on your shoulders, and yes, your gut might be a little visible, but that's because you have one, and there ain't no hiding it. Whether it's board shorts or a T-shirt, stuff just has to fit right. You don't want your shorts to be too big that they'll easily come off in the water, and you don't want to be swimming in your tee, either.