I kinda find this topic somewhat sensitive but I reackon it doesn't hurt to go for being toned up and ship shape! I worked with a girl that was overweight and she decided to lose weight and apply to airlines. She hasn't got through yet but she says that doesn't ever have to worry if it was because of her size. She feels so great and has more confidence now.
I have heard from Gulf interviews in Australia that some applicants were told to lose some weight.
I guess the general rule of thumb is weight in proportion to height.