HIIT vs. continuous aerobic training: Is there a clear winner? Original paper

In this meta-analysis of randomized controlled trials, high-intensity interval training and continuous aerobic training had similar effects on body fat, but high intensity interval training was better for increasing VO2 max and reducing blood glucose.

The effect of high-intensity interval training (HIIT) compared to continuous aerobic training (CAT) on body fat percentage and abdominal visceral fat mass (primary outcomes).

The secondary outcomes were body weight, BMI, maximal oxygen uptake (VO₂max; a marker of aerobic endurance), and the levels of fasting glucose, total cholesterol, and triglycerides.

A total of 379 men and women (ages 19–51) with overweight or obesity.

A meta-analysis of 11 randomized controlled trials was performed. In the HIIT interventions, the participants exercised at 85%–120% of maximum/peak heart rate or maximal/peak oxygen uptake during the active periods (which were followed by recovery periods) and performed 3–5 weekly sessions with an average duration of 27 minutes. In the CAT interventions, the participants exercised at 50%–75% of maximum/peak heart rate or maximal/peak oxygen uptake and performed 3–5 weekly sessions with an average duration of 44 minutes. The intervention duration ranged from 5 to 16 weeks.

HIIT was as effective as CAT for reducing body fat percentage and visceral fat mass, with the certainty of evidence rated as low for both outcomes.

Moreover, HIIT was as effective as CAT for reducing body weight, BMI, and triglycerides. However, HIIT increased VO₂max (small effect size) and reduced the levels of fasting glucose (medium effect size) and total cholesterol (small effect size) more than CAT.