Every human is different, but yes I believe that's too much. If he had said, "I exercise 5 days a week, take 1 week off every 3 months and 2 consecutive weeks off per year." Then that is different. But he said he runs a 5k EVERY SINGLE DAY, and that is far too much abuse for a human body. The most insidious symptom of overtraining syndrome is a compulsive need to exercise.

If this individual is overtrained, his body will find a way to stop him. He will become ill from immune suppression or injured from the constant stress that never fully heals, or too depressed to exercise at all.

Body builders have a saying something like, "Muscles are made in the bedroom and the kitchen."

Also, there is some (not much) calorie burning in running 10K vs walking.

I'm not a beginner in running. Been running for more than two years but I find it hard to run 10k/day unless I don't have a job and don't go to work. I do the same I run on MWF and lift TThSat and that routine is ok for me. But running everyday is different.