You should not eat to much but just the right amount as before Ramadan. The ruling do not change because you are meant to feel the hunger than the poor feel everyday and so you should be grateful for what you have been blessed with. Also over eating has bad side effects. Those who show moderation in eating find greater pleasure in their food than those who overindulge.
O children of Adam, take your adornment to every mosque. Eat and drink, but be not excessive. Indeed, He does not like those who commit excess. [Sûrah al-A`râf: 31]
The hadith of the prophet (PBUH):
The child of Adam fills no vessel worse than his stomach. Sufficient for the child of Adam are a few morsels to keep his back straight. If he must eat more, then a third should be for his food, a third for his drink, and a third left for air. [Sunan al-Tirmidhî and Musnad Ahmad (17186) and authenticated by al-Albânî in Sahîh al-Jâmi`]
Luqmân said to his son: “O my son! If the stomach is full, one’s mental processes go to sleep, one’s wisdom is dulled, and one’s limbs refrain from worship.”
Umar observed: "Whoever eats a lot finds no pleasure in the remembrance of Allah."