My kitties are both tubby bubbies too, one is on dry food only and eats only a small cup per day, however i think the biscuits must be high in fat, as she has gained on these, I also read cats that are on dry food only tend to gain more weight,not sure exactly why, i tried the low cal variety of her biscuits and she would not eat them, so it is difficult, the weight management purina ones only keep their weight at bay , won't help them loose any, perhaps some advice from the vet might be in order, I too want both my cats to loose a few pounds. Good Luck.