"H.I.I.T" stands for "High Intensity Interval Training."  You will need it in your life if you want a quick, high energy, fat-burning workout that takes only 1/2 hour.
In that case, who doesn't need this?
Choose a workout you like to do:  walking, running, biking, indoor cycling, elliptical.  After a 3 minute warm up, go as fast as you can for 30 seconds, then recover for 2 minutes.  Repeat 10x.  Cool down and stretch for 5 more minutes.