I have cut back a bit on running volume since my HM and 10K a few weeks ago - but now starting to build up again, mostly with easy running but a little bit harder at parkrun and a short fartlek day once per week.
This past week I have completed 2hours 30 minutes of running ( nearly all non-stop) , 20klms and Garmin tells me it cost 1500 calories. 1500 cals per day is around my basal metabolic rate for an otherwise sedentary life. I may be currently eating/drinking more than or less of this, don't really know. But this means that I have essentially used up one whole day's food intake - at least as much as I would be supposed to consume to cover my BMR.
Is this a valid way of looking at things?? Am intending to increase my weekly volume at least another hour to 3hours 30mins. During my training for the HM, I did one day of 3&1/2 hours!!