Reversal Rings 3 -- Lost and Found
        by Morpheus, as are the following two

Steve, depressed and overweight, living in the doldrums of an inescapeable life, finds the ring that was previously dropped by the 6yo girl who found himself in 14yo Jamie's body. Putting it on, he finds himself in Ross's girlfriend, Shiela.

This is quite a positive development for Steve. Shiela, once she tries calling home and hears her own voice, decides that she never really was Shiela but instead was always the overweight slob Steve. So she decides to get on with his life.