The bird is three years old, correct? How long have you had it? Which type of Lovebird is it; peachface, etc.? What do you normally feed it? You say "different food". What did you change? Tell me about it's totaly dailey diet. Do you offer anything other than seeds and millet? Has there been any change in it's behavior? More active, less active, keeping feathers fluffed, etc.? Is she still using her perches or does she spend anytime sitting on the cage floor? Are there any other changes in appearance other than you feel it looks thinner?Have you seen any change in the appearance of the droppings? Have you ever weighed your bird and tried to keep a weight chart? Can you run your finger gently down the keel bone and tell me as best you can, how it feels? Meaning is it sort of deep in the chest, or is it very easy to feel, or what. This extra information and anything else you can thing of to add will help me give you my best possible answer and advice. Thanks, Patricia