I bought a stallion that was really "over-conditioned" - as in FAT - and he had a HUGE crest. He is cresty anyway by nature, but this was really scary because of the risk of founder. I immediately put him on the "Whinny Craig" program of weight loss!!!! He had been getting free-choice dairy quality ALFALFA - no wonder he was so fat - AND grain too, a sweet-feed. YIKES!!!! So when he got here, I changed him to NO grain except a tiny amount of plain rolled oats and plain rolled barley, and GRASS hay. Let me tell you, those first months were brutal for him. He has now been here almost 2 years, and you should see him these days! He is a different horse. He gets free choice grass hay, and that tiny amount of oats and barley, and he looks great. Now, some might consider him thin! He does not have huge rolls of fat along his back like he used to. But, cresty horses usually are PRONE to founder and you do them no favors by trying to make them look fat! Also, he has a different conformation, that is more slender by nature. He does not have that "stock horse" look, he has more of that "race horse" look. So to keep him at a correct weight, he needs to look slimmer than a horse with the bone structure of a stock horse. If your horse has that type of build, don't try to keep a crease down her back - it will mean she is overweight. If she has the stock-horse type build a crease down her back might be correct. Anyway I suggest a diet! Talk to your vet and see if you can come up with a good one.