CRJ200 must declare a fuel emergency and land enroute. Appear to have taken off without planned fuel on board.

Narrative

Our flight was running about 15 minutes late. Nearly immediately after we boarded the aircraft; the gate agents started the boarding process. We boarded 45 adults and 1 child. As we were preparing for departure at the gate; we commented on how cold it was outside (approximately 10 degrees wind chill) and remarked how the wind was blowing directly into the cockpit. After getting our required paperwork from the outside agents; we closed the cabin and cockpit doors and finished the pre-start and engine start checklist. After receiving clearance; we pushed back and taxied to runway for departure; performing all checklists. About 55 minutes into the flight we were getting ready to perform our hourly fuel check. We noticed we were indicating roughly 1200 LBS of fuel on board. At that time we did not have any idea why there was so little fuel on board. We quickly decided that we needed to make an emergency diversion and landing and figure out what the problem was. We were right on top of ZZZ. The Captain instructed me to declare an emergency; seat the passengers; and brief the Flight Attendant. We obtained a clearance direct to ZZZ and started a descent. The Captain made 1 final announcement to the passengers explaining to them that we were making a precautionary landing due to what we believed to be a fuel indicating problem; and that we would be on the ground within 5 minutes. I completed the descent and before landing checklist on final approach to the runway. We did 1 circle over the FAF of the back course approach to lose the rest of our altitude and performed a normal flaps 45 degree landing. We then parked at a gate that is used to handle RJs. We initially kept the people on the aircraft until we worked out the details with the agents and the local TSA. Our company then instructed us to secure the airplane; thus deplaning. Later that day; contract maintenance checked out the aircraft for a fuel leak but found no indication of one. It was at this time we were led to believe we may have not departed with the proper amount of fuel. The Captain and I have spent many hours replaying the moments leading up to this event. We truly believe we completed the pre-start checklist; where we check our fuel load; and we are sure when we departed we were confident we had enough fuel for the flight. Working under the assumption that we were incorrect in either stating the amount of fuel on board during our checklist or stating the correct amount but thinking that was what our release called for; I can offer some possible theories as to why this may have happened. Possibly; we stated whatever fuel quantity was actually on board the aircraft correctly in the checklist but being pressured to get the flight out on time or just distraction due to the extreme cold air blowing inside the cockpit from the boarding process we simply overlooked the required amount. Additionally; our checklist requires both the Captain and First Officer to state the amount of fuel actually on board the aircraft; and by stating 'confirmed' we confirm that we have enough fuel per the release. I feel this checklist format could use some improvement. If the checklist required one of us to state the fuel on board and other to state the fuel required it may have brought to our attention a possible oversight.