When shooting photos of friends, objects closer to the lens are enlarged (subject is sitting for instance). Is there any way to get an accurate representation of the entire subject?

That's what's called perspective. If you want the person's legs to look more in line with the size of the rest of the person take the picture from further away at the same angle, i.e. high or low, either with a telephoto lens or, if with a regular lens, crop the photo as if it were taken closer.

You will get a more natural look, if you are moving further away and are using the tele lens instead of the wide angle lens, if possible.