I do 30sec stair sprints - 1min walk.
When I started it was for 20mins then I worked up to 30mins. It shredded the fat off me.
After about 8weeks I was recovering to easy and didn't feel as puffed so I recently bought a weight vest that can hold 30kg.
Now I do 20mins stair sprints with 10kg in the vest. When I get to 30mins il add another 5kg and start over again.
Got to keep the intensity up to keep getting results, I was surprised the additional 10kg in the vest almost kills me but the results are awesome!