AN ACR CAPTAIN REPORTED FINDING HIMSELF IN A MIN FUEL STATE FOLLOWING MULTIPLE ATC SPEED AND ALTITUDE CHANGES.

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MINIMUM FUEL ENRTE. FACTORS INCLUDED BEING HELD DOWN FOR A LONG LENGTH OF TIME BELOW FILED CRUISING ALT AND MULTIPLE ATC INSTRUCTIONS TO SLOW DOWN THEN SPD UP OVER 20-30 KT RANGES. WX/TURB WAS A FACTOR IN THE SPD CHANGES. CONSTANT LIGHT; OCCASIONAL MODERATE CHOP AND TURB WAS RPTED ALL ACROSS THE REGION AT MOST ALTS BTWN FL200 AND FL360. THE THIRD TIME WE WERE TOLD TO SPD UP AFTER A SPD REDUCTION I NOTIFIED CTR WE WERE UNABLE DUE TO BEING ON THE EDGE OF A MINIMUM FUEL STATE. AFTER A MOMENT; THE CTLR CAME BACK AND NOTIFIED ME THEY WOULD CARRY OUR FLT AS BEING 'MINIMUM FUEL.' A SUBSEQUENT CTLR ASKED WHY WE WERE MINIMUM FUEL AND I EXPLAINED ABOUT HELD DOWN AND SPD CHANGES. ACFT ARE DISPATCHED WITH A CONSERVATIVE FUEL LOAD AND A SMALL ALLOWANCE FOR CONTINGENCIES. ENRTE FACTORS EXCEEDED THE SMALL ALLOWANCE. WE NEED SOME FORM OF SYS TO NOTIFY DISPATCHERS OF EXPECTED ADDITIONAL ENRTE DELAYS. ON ANY OTHER DAY OUR FUEL WOULD PROBABLY HAVE BEEN SUFFICIENT DESPITE BEING HELD DOWN; BUT THE MULTIPLE SPD CHANGES; ESPECIALLY SPEEDING BACK UP; REALLY HURT OUR FUEL PERFORMANCE. IF DISPATCHERS WERE AWARE OF ADDITIONAL DELAY FACTORS ON A CERTAIN SEGMENT OF ROUTING; THEN ADDITIONAL FUEL COULD HAVE BEEN ADDED. AIRLINES ARE TRYING TO CONSERVE FUEL THROUGH BETTER PLANNING; BUT THEY NEED TO HAVE A REALISTIC IDEA OF ANY ADDITIONAL FACTORS TO CONSIDER. SIMPLY ADDING 500-1000 LBS BECAUSE ATC 'MIGHT' INDUCE DELAYS ISN'T THE MOST EFFECTIVE WAY TO PLAN.