HIIT (High-Intensity Interval Training) is not a branded program — it’s a training principle you can apply to almost any exercise, and it has some of the strongest research behind it of any format on this site, especially for time-efficiency.
Quick Facts
How the Evidence Compares
Why HIIT Works
HIIT increases energy expenditure both during the workout and afterward, through elevated post-exercise oxygen consumption — your body keeps burning extra calories for hours after you finish. It also improves insulin sensitivity, helps preserve lean muscle mass better than steady-state cardio alone, and affects appetite-regulating hormones like ghrelin, which is part of why it’s specifically effective for visceral fat.
A Simple 20-Minute HIIT Circuit (No Equipment)
| Exercise | Work | Rest |
|---|---|---|
| Jumping jacks | 30 sec | 15 sec |
| Bodyweight squats | 30 sec | 15 sec |
| Mountain climbers | 30 sec | 15 sec |
| Push-ups | 30 sec | 15 sec |
| High knees | 30 sec | 15 sec |
Repeat the full circuit 4 times for a complete 20-minute session — see our full no-equipment belly fat routine for a more detailed version of this approach.
HIIT vs. CrossFit vs. Insanity: What’s the Difference?
HIIT is the general training principle; CrossFit and Insanity are specific branded programs that apply HIIT principles within their own structure, equipment, and (for CrossFit) group class format. You can get similar benefits from any of them, or by simply applying HIIT structure to your own bodyweight routine at zero cost.
Who Should Try This
You want maximum benefit in minimum time and are comfortable with genuinely uncomfortable, all-out effort during the work intervals.
High-impact HIIT moves can stress joints; low-impact variations exist, but building a base with steady-state activity first is often safer.
FAQ
How often should I do HIIT per week?
Most guidance suggests 2 to 3 sessions weekly, since the intensity requires more recovery time than moderate steady-state cardio.
Is HIIT better than steady-state cardio for fat loss?
Research shows HIIT can produce similar or better fat loss results in significantly less total time, largely due to the elevated calorie burn continuing after the workout ends.
Can beginners do HIIT?
Yes, with modified intervals and lower-impact exercise choices, though building some base fitness with steady-state activity first is often a safer starting point.
