Captain reported a fuel leak from the left engine resulted in a diversion and single engine landing.

Narrative

At top of climb when we started out navigation log we immediately noticed we were 1;000 pounds over burn. After some investigation we suspected a fuel leak on the left side. Captain was deadheading so I had him look for fuel spray; he couldn't see any possibility because it was so dark out.[The deadhead Captain] and I flew together at our previous company so I had him come up front as another set of eyes. He was a great help setting up radios; the HUD and helping with over all situational awareness.I had my FO (First Officer) take the jet and ATC while I ran the Fuel Leak QRH; talked to Dispatch; the FAs (Flight Attendants); gave the passengers a PA regarding our situation and got the jet headed for ZZZ2. After we got the engine secured we got set up via vectors for the Runway XXL ILS at ZZZ2. We had ATC give us vectors while I ran the One Engine Inoperative Landing checklist. [The First Officer] made a beautiful single engine landing and we taxied to the gate. CFR (Crash Fire Rescue) followed us to the gate and monitored the left side. Deplaned the passengers who were all very positive. Made and took several phone calls to Scheduling; [flight operations]; Maintenance; ZZZ3 Chief Pilot. Met with ZZZ2 CFR Chief. Was plane side while Maintenance opened the left cowl. Appeared to be fuel outside of cowl; on the wing; in the tailpipe and once the cowl was open there was a significant amount of fuel moisture throughout the inside. I conducted the FOM post flight debriefing with the entire crew in the jetway including [the deadhead Captain]. Everyone understood the situation; felt communications between the cabin and cockpit was good and were all okay to continue to ZZZ on a good jet. When I got to the assess landing per the One Engine Inoperative Landing QRH I knew we would fit on Runway XXL at 11;000 ft. and did not run data. I should have ran the data but was ready to get the jet on the ground. However; with the steep Glide Slope at 3.54 degrees and no LTP (Landing Threshold Point) discussed this could produce an unplanned problem. Also if I would have ran the data I would have entered the landing weight; as of right now I have no idea if we landed overweight. I did discuss this with maintenance after landing and told them the landing was very smooth if they had to do an inspection. Take the extra two minutes and run landing data. This will get you in the mode to talk about LTP and weight considerations.