Well Fed

Well Fed, Plenty Satisfied, and Exquisitely Stuffed are buffs granted to the player depending on the food item consumed. The buff slightly improves all stats (listed below). Additionally, in, life regeneration will only be fully effective while the player is under the effects of this buff.

Well Fed
Well Fed grants the following boosts:
 * +2 defense
 * +2% critical hit chance for all attacks (except from Summon weapons)
 * +5% melee speed
 * +5% damage (including summons)
 * +0.5 minion knockback
 * +20% movement speed

Plenty Satisfied
Plenty Satisfied grants the following boosts:
 * +3 defense
 * +3% critical hit chance for all attacks (except from Summon weapons)
 * +7.5% melee speed
 * +7.5% damage (including summons)
 * +0.75 minion knockback
 * +30% movement speed

Exquisitely Stuffed
Exquisitely Stuffed grants the following boosts:
 * +4 defense
 * +4% critical hit chance for all attacks (except from Summon weapons)
 * +10% melee speed
 * +10% damage (including summons)
 * +1 minion knockback
 * +40% movement speed

Causes
The complete list of food items that grant these buffs are listed here.

Tips

 * This buff is extremely useful as it is easy to obtain, extremely versatile, and has a long duration.
 * During Halloween, Pumpkins for Pumpkin Pie are plentiful, and even at other times the Dryad can supply Pumpkin Seeds to farm them. Other food items can be crafted or picked up from varied sources.
 * On the flip side: An old proverb says "Give a man a fish, and you feed him for a day.  Teach the man to fish for himself, and you feed him for a lifetime".  While fish in Terraria don't quite last a full day, even a modest amount of fishing for other purposes can certainly provide enough fish to keep a player well fed despite the shorter duration.
 * Most players should carry a stack of "food" items, and try to keep the buff always active. The movement bonus alone would make that worthwhile, but in  food is even more important, as it is required to regenerate health normally.  In any mode, the small but broad boost to combat abilities comes in handy.
 * Use this buff before boss fights or venturing into dangerous areas to gain a cheap and easy advantage. The movement buff makes it worthwhile even for exploring and mining.
 * There is a bug in 1.4.0.2 version with "Exquisitely Stuffed" buff. It gives no damage increase for ranged type of damage.

Trivia

 * The Cooked Marshmallow is currently the only item to have the same duration on all platforms.