Years ago, my very overweight much younger sister lost a lot of weight on the phen-phen diet. I was glad for her until she dropped by the house to give me her size 14 "fat" jeans. And they were the cheapy kind...
Now she weighs about 300 pounds and I am still fit and wear a size 14 at the age of 50. I feel bad for her yet I have never forgotten how she made me feel when she was skinny.
I also had a friend that had gastric bypass 3 years ago and she used to be kind and nice. When she lost all her weight, she became obnoxious and a smart ass. I can hardly stand to be around her and I am not the only one that feels that way.