Date: 201701
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: Mixed
Weather elements / visibility: 10
Light: Night
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Takeoff / Launch
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Time Pressure; Fatigue
Second reporter function: First Officer; Pilot Flying
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented
Contributing factors: Weather; Human Factors
Primary problem: Human Factors

Narrative: It was the last leg of a four day trip. We were late. Bad weather the entire four day; and both the First Officer (FO) and I were getting tired. We had an inoperative APU which was a further distraction as we had to talk to the Ground Crew and ensure the correct ground start procedure was followed; and also figure out where the cross bleed start would be accomplished. As we were doing all of this and starting the Before Start Checklist we got an ACARS from Dispatch saying we were to fly at FL 280 and CI 100. I called them on the phone. [Dispatch] told me that we were over fueled and needed to burn off 2000 pounds of fuel; or we would be overweight for landing. With the current routing that was filed; we couldn't have burned off that much fuel. I asked if we could defuel and the Agent said it would take too much time. [Dispatch] then rerouted us over a longer route that would burn the fuel off.We got a second Dispatch Release; started to go over it; and were interrupted by the Agent; giving us yet another Release. Also we were interrupted by Flight Attendants and Ground Crew who wanted to get going and wanted to know what the delay was. As I started to look at the third Dispatch Release; Clearance Delivery called with our amended clearance. I stopped looking at the Dispatch Release numbers to focus on the clearance. The clearance was incorrect; because ATC couldn't believe we would want such a LONG route to go to ZZZ1. We explained our predicament; and got the clearance as filed. We loaded the new routing and briefed it carefully. By now both my FO and I were clearly in the Yellow and trying to get back into the Green. By that time; Passengers had been on the aircraft and waiting at least 20 minutes; and were getting irritated. At that point we did the Before Start Checklist and got the loading schedule. I was rushed; but trying to do things methodically; however; I missed going over the third Dispatch Release carefully enough and comparing the zero fuel weight and takeoff weight with what was on the loading schedule. There was a 16;345 pound difference in the takeoff weight and 16;137 pound difference in the zero fuel weight. Dispatch had planned us with a full Passenger load; but we only had 75 Passengers. I missed it. The good news is we were at the actual weight on the loading schedule and not the planned weight on the Dispatch Release. Once airborne I discovered the error when I had a chance to look at the Release more carefully; and contacted Dispatch immediately. I tried to reach ZZZ Operations but no one answered the radio. We determined the loading schedule was correct and landed uneventfully in ZZZ1. All I can say is I'm sorry. I have learned a lot from this flight and will be more diligent in the future; slow down; and try to minimize the risks of fatigue; multiple interruptions and changes to our normal flow.We were late and felt rushed. We needed to slow down. We were getting tired; it was the last day of a long hard four-day trip. We could have called in fatigued; drank coffee or eaten something. We were distracted by Ground Crew and Flight Attendants and Agents as we were trying to sort out the new route and communicate with Dispatch. We could have told them to leave us alone while we did our job. I think the other Employees might be made aware that distracting the Pilots at times like this adds stress and causes errors.


Second narrative: Pushed back and taxi out to start cross bleed. Started takeoff roll and at V1 rotate I pulled back and the yoke was very heavy; I told the CA that it was very nose heavy. Trimmed out and continued on the departure. At cruise we discussed what may have happened and began looking at the numbers between the release and the load sheet and discovered a discrepancy of over 16K LBS. Dispatch had planned the flight full and in actuality we only had 75 passengers. We sent ACARS back and forth with dispatch and determined the load sheet was correct and landed uneventfully at ZZZ1.Minimize distractions from crew and ground OPS; slow down and realize that we were getting tired and should slow down more and be extra diligent when loading performance numbers. Other work groups IE. attendants and OPS need to be made aware of interrupting pilots during checklists.


Synopsis: B737NG flight crew reported multiple distractions along with being late on the last leg of a fatiguing four day trip which resulted in them departing weighing less than what was shown on the release.