I have two cats, Sid and Nancy (brother and sister), They are just over a year old now. Nancy is chubby and Sid is skinny and has a sensitive tum so a lot of cat foods makes him sick. They are on complete dried food. I've tried feeding nancy on diet food and giving sid his normal stuff separately but he will have a couple of mouthfulls and then doesn't want any more and if he does manage to sneak any of the diet stuff he's sick. He likes to nibble throughout the day and will resist all attempts to persuade him to eat a full portion at meal times, and even when he is allowed to eat when he wants he remains really quite boney. Nancy will fill up at meal times and then nibble all day as well and she is proper little chubster now!
Both are happy and active with glossy coats etc although nancy is, ahem, not as light on her feet as she used to be and isn't able to leap up to high places.
Help!! How do I bulk him up and slim her down!?

