[scheveningen]

30 kcal per minute would be very difficult to sustain except for a very short burst of time (like 2-5 minutes) in a peak performance scenario (such as an end-of-season race that the athlete is very well tapered and rested for).

My personal numbers for my regular training runs are about 11-12 kcal per minute. I can exceed 15 kcal per minute for very hard workouts or racing but I cannot train appropriately while doing that regularly. I'm a relatively seasoned runner but I don't focus on 800m-1500m which is where it might be possible to see numbers exceeding 20 kcal per minute.

In order for this to make sense for the purposes of lifestyle modification, you also have to subtract the calories that you would have burned had you not been exercising. IE if you had not run for that 30 minutes, you would still have been burning calories, either completely sedentary BMR or some other NEAT. This makes it even a worse deal to exercise for the sake of burning calories.