To many carbs do a good job of making the skin weak, that surface fat layer is really what kills ya it seems. I used to weight 350 and I'm now down to 210, stretch marks were a problem till I started eating lots of meat and veggies. Now the only stretch marks you can see on my body are the ones on the air sack of a stomach I have now, which will be removed soon enough. I'm half black and very athletic though, I think stretch marks stand out quite a bit more if you have light skin.
People with a stretch mark problem could really bennifit from a toning diet, it tightens the skin quite a bit.