HIIT vs Cardio: How to Choose the Right Training Style for Your Routine

What Does the Research Say About Fitness?

One of the strongest reasons to perform either type of exercise is to improve cardiorespiratory fitness.

VO₂max or VO₂peak is commonly used to measure aerobic capacity. It reflects how effectively the body can take in and use oxygen during demanding physical activity.

An umbrella review published in 2024 examined 24 systematic reviews and meta-analyses covering 429 primary studies and almost 13,000 unique participants. It evaluated HIIT against non-exercise controls and continuous forms of exercise, including moderate-intensity continuous training. The review found evidence that HIIT improves cardiorespiratory fitness in adults, although the size of the effect varies across populations and training programs.

A separate meta-analysis of young and middle-aged adults found that both HIIT and moderate-intensity continuous training improved cardiorespiratory fitness. HIIT had some statistically significant advantages for VO₂peak, but the researchers noted that the practical significance of those differences was limited.

So when looking at HIIT vs cardio, both can be effective for improving aerobic fitness.

What About Fat Loss?

Fat loss is where many comparisons become too simplistic.

HIIT can help reduce body fat, but it should not be described as an automatic replacement for traditional cardio.

A systematic review and meta-analysis of adults with overweight or obesity found no significant difference between HIIT and moderate-intensity continuous training for body weight, BMI, waist circumference or body fat mass. The researchers did find a moderate benefit from HIIT for insulin sensitivity, but concluded that more evidence was needed.

More recent research has produced somewhat different findings.

A 2026 network meta-analysis examined 18 randomized controlled studies involving adults with overweight or obesity. HIIT performed for at least 75 minutes per week was associated with reductions in body-fat percentage and waist circumference and improvements in VO₂max compared with control conditions. The researchers described the evidence as moderate to low certainty, and the included interventions lasted only 8 to 16 weeks.