A systematic review examined high-intensity interval training (HIIT) in healthy, sedentary adults aged 18 to 64. It included 2,075 participants from studies lasting four weeks or longer, comparing HIIT to no exercise and to moderate-intensity continuous training (MICT). The review focused on outcomes like fitness, blood pressure, waist size, and triglycerides.
The review found that HIIT likely increases cardiorespiratory fitness and reduces waist circumference compared to no exercise. Compared to MICT, HIIT may slightly improve fitness but shows little to no difference in waist size, blood pressure, or triglycerides. No studies reported adverse events, but it's unclear if they actively monitored for safety issues.
Readers should be cautious because the studies had relatively few participants, lacked detail on methods, and provided uncertain evidence for some outcomes like blood pressure. This means the results are not definitive, and more research is needed to understand long-term effects. For now, HIIT appears to be a potentially effective exercise option for improving fitness and waist size in sedentary people, but it's best to consult a healthcare provider before starting any new workout routine.