My aunt used to be obese, and she developed granular parakeratosis inside the folds of her fat. All that sweating and chaffing caused a brown scaly rash to appear, and this motivated her to lose the weight.
She did use steroid cream in the meantime to control the rash, but she knew that it would occur over and over again unless she got rid of the fat folds. I think the rash caused her to become disgusted with herself.
It actually worked in her favor, because she lost a hundred pounds and got down to her ideal weight. She hasn't had any bouts with parakeratosis since she got rid of the folds.