A hack I like to do with treadmills is to go 1.5-2 miles per hour and have an incline of 20-30%. You burn 600-800 calories but your going at walking speed. I call it the hiking simulator.

I've never seen a treadmill that goes over 15% grade. 30% is almost a stair stepper.

Ah it is a pretty unique treadmill: https://www.freemotionfitness.com/cardio/incline-trainers

They call it an incline trainer

With stair steppers I found it a lot harder to sustain it for the same nominal calorie count. But going up a %30 incline vs a stair stepper might be the same difference between an elliptical vs running.

And at 9 mph, they will burn over 1,000 kcal.

https://www.runnersworld.com/tools/calories-burned-calculato...

6:40 per mile is a pretty intense pace for most people to keep up for an hour.

Most people don't run much. Just as with hiking, strength straining, gymnastics and other sport, ability grows with training.

Another option is simply running longer. Few people who aren't overweight couldn't train up to 90 minutes. Given that there's overhead in showering and changing clothes, going longer, fewer days per week does have an efficiency of sorts.

Edit: Ideally one avoids having a completely irresponsible diet, however just training can do a lot and can also blunt the appetite after a certain threshold.

Running a 6:40 mile for an hour is outside of what most dedicated runners can achieve.

Don't be ridiculous. Ed Whitlock ran that pace for an entire marathon at the age of 73.

If you're dedicated, under 50, free of serious ailments and anywhere near the weight range this thread used as an example, it's something you can almost definitely achieve for a single hour.