The total work number that shows up on strava with a power meter is what I take as calories burned. When I don't ride with a PM the estimated total work number still seems more reasonable than the one given for calories. I did a casual 2 hour ramble with friends that had a few short efforts and strava estimated the total work at 1024kJ but the calories at 1943. On a group ride where I had a power meter it said I burned 4069 calories in 4h10 but the power meter total work is only 2765kJ which seems much more realistic for me.
If I'm riding at lower intensities hopefully more of the "fuel" is coming from body fat stores and I less about eating during those periods... and on short rides I don't eat or drink any calories.