Very possibly teething pains. My baby used to eat fast and a lot too, but since around 8.5 months, when teeth started emerging, her eating habits has changed so much too. Now at 13 months, everytime a new tooth is starting to emerge, she hardly eats.. then when the pain gets better, she eats more. Certain types and textures of food also gives her more comfort. When it was quite painful, I used to give her a cold teether to bite on for a few seconds before giving her some food, so that her gums were less sore