HIIT or high-intensity interval training is done with periods of very intense exercise interspersed with recovery time, while steady-state is done with a relatively stable intensity over a longer period of time. Both can help improve fitness and use energy, including from fat. The difference is more pronounced in the training pattern, intensity, duration and body load after exercising.
If the main goal is to reduce body fat, don't get too caught up in thinking that one type of cardio is definitely superior. Long-term fat loss is greatly influenced by energy balance, diet, daily activity, sleep quality and exercise consistency. HIIT can appeal to people with limited time, while steady-state may be more comfortable to do for longer and easier to maintain. The best choice is usually exercises that suit your body condition and can be done consistently.
