I feed my guys Science Diet Light and boy has it made a difference!!
Cookie is small boned, but we kinda let her get fat. She's been on the Light food now for 2 years and in the first year she went from 13 pounds to 10 pounds and this year went from 10 pounds to 8.5 pounds! Now she looks great!
As for the others, the Science Diet Light helps them to maintain their weight so they don't get any fatter. Pumpkin is around 8-9 pounds and Tama is 6 pounds.