behavior and diet?

My 4 year old son is very aggressive toward certain children ... he's singled out one (or possibly) 2 boys in particular to torment?   I don't know what to do.  He is aggressive; and cannot seem to sit still in many situations.  Yesterday he climbed off the couch, interrupted my playing with his 3 yr old sister and threw a toy at me -- no reason, no warning, just smack -- Charlie Brown to the head.
I'm concerned that he's a bully, and won't have any friends.  His teachers say that he's provoked, that the boy he attacks is sneaky ... however, the boy is now telling everyone he can that he "hit" "bit" "kicked" me when the teacher isn't looking!?    He's 4 1/2 -- and his behavior is gettting worse, not better.   He's in pre-K with 5 other children.   It's an engaging / structured curriculum that keeps him busy and on a schedule 80-90% of his day.  
I've heard that limiting gluten, sugar, and many other things can help ... I've also read, now, something about fish-oil?   I'm willing to try anything -- other than meds at this point!?   All the books I've read, websites, child psych stuff I've tried hasn't worked.  Rewards, punishment, time out, sticker charts, talking, drawing, you name it ...  HelP!?

[Renee Radenberg]

There have been numerous studies of diets with agressive behavior, however, nothing has been scientifically proven. The best management is behavioral modification and medication.

[EdieMarie]

I took my son to a behavioral Therapist at 4 and he suggested I put him in "Taekwondo"  to teach him self control and self discipline from  a young age.  He also had some great suggestions to use at home.  But the bottom line is his aggressive behavior is unacceptable.  My son is 12 now and still has a lot of impulsive behavior.  My son has Asperger's/PDD/ADHD/ and Auditory prossing disorder.The earlier you get a diagnossis the better you can understand him and deal with his behavior.  Sometimes they can't control there impulses and need help and close monitoring even at 12 my son struggles with it.but diet really helps!

After many years of keeping my son off sugar I found out that carbs like ceareal bars and crackers turn to sugar and also cause a surge of energy.  Juce is also full of sugar.  Glutin free diet is hard to do but fast food and packaged food is full of glutin.  I do a very healthy organic diet Subway instead of fast food water instead of other drinks.Protien for breakfast instesd of cereal so the carbs don't turn to sugar as soon as they get to school.

I know what you are going through and it is tough.  Please don't rule out meds all together...there are some that really help and at some point down the road they may be needed.  I tried all homeopathic remeadies first and they really helped.

Good Luck!