My father isn't svelte on paleo, but he looks SO MUCH BETTER. Ditto for my mother. I don't think they are going to regain the slimness they had in their twenties, but everyone notices they look better and people have adopted paleo because of them.
But then again, they aren't going around marketing paleo as a weight-loss diet fad. On my own site I've never promised people they will become lean on paleo. There is no study showing that this diet has that ability. But people have the potential to return to a more comfortable weight and feel much better. I just read an advance copy of "Why Women Need Fat" and I was amazed that the book didn't promise women that their dietary regimin regimen would make them thin. The real struggles diet book authors themselves encounter are a testament to how hard it is to get lean, particularly when you have been overweight for a long time, are a woman, or are older.
That said, now that I'm spending more time with my father, I do think he could lean out more. I had to explain to him today that fried chicken is usually not paleo because the breading is BREADing and it's almost always fried in PUFA.