Key messages
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Physical inactivity costs the world an estimated USD (US dollar) 53.8 billion each year. Exercise is a simple, affordable, and effective way to reduce the risk of heart disease, especially for people who are not active. However, many people don't meet the level of physical activity recommended by the World Health Organization (WHO).
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Compared to no exercise, high-intensity interval training (HIIT) probably improves fitness and reduces waist size, but we found no clear differences between no exercise and HIIT for systolic blood pressure (the top blood pressure number), the ratio of waist to hip size, or circulating triglycerides (a type of blood fat). Compared with steady, moderate-paced exercise, HIIT may improve fitness slightly, but we found no clear differences between the two types of exercise for systemic blood pressure, waist size, the ratio of waist to hip size, or circulating triglycerides.
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Our findings suggest that HIIT may be as effective as moderate-intensity training to improve heart health and reduce the risk of conditions like type 2 diabetes. However, more high-quality evidence is needed to be confident in these findings.
What is high-intensity interval training?
High-intensity interval training (HIIT) is a type of exercise training that involves repeated short periods of hard/intense exercise followed by rest periods.
What is cardiometabolic health?
Cardiometabolic health refers to the health of the heart and blood vessels, as well as how the body processes energy from food. It involves key factors like blood pressure, cholesterol levels, blood sugar, and bodyweight. When these are in a healthy range, the risk of developing conditions like heart disease, stroke, and type 2 diabetes is much lower.
What did we want to find out?
We wanted to find out if HIIT was better than no training or moderate-intensity continuous training (MICT) to improve markers of cardiometabolic health in inactive people.
What did we do?
We searched for studies that investigated the effect of HIIT compared to no exercise training or MICT on indicators of cardiometabolic health. We were interested in studies that looked at inactive but otherwise healthy people. We summarised the results of the studies and rated our confidence in the evidence based on factors such as study methods, sizes, and the amount of information presented.
What did we find?
We found 58 studies involving 2075 inactive adults. The number of participants in each study ranged from 14 to 90, and the training programmes lasted from four weeks to 16 weeks. Thirty-five studies compared HIIT with MICT, 11 compared HIIT with no exercise, and 12 included both comparisons.
Main results
Compared with no exercise, HIIT likely improves VO₂max, which reflects overall heart and lung fitness. HIIT also leads to a small reduction in waist size. However, HIIT probably has little or no effect on the ratio of waist to hip size, and may have little or no effect on triglycerides (a type of blood fat). The evidence for HIIT on systolic blood pressure (the top blood pressure number) is very uncertain.
Compared with MICT, HIIT may improve VO₂max slightly. There may be no difference between HIIT and MICT for systolic blood pressure and triglycerides, and there is probably no difference between the two types of exercise for waist size and the ratio of waist to hip size.
No studies reported important long-term health outcomes such as heart attacks, strokes, or deaths.
What are the limitations of the evidence?
We have little confidence or moderate confidence in most of our results, and further research could change our conclusions. Three main factors reduced our confidence in the evidence. First, there was variation in how people in the studies responded to the treatment they received. Second, some studies were very small, and for some outcomes, there were too few studies to be certain about the results. Finally, people in the studies were aware of which treatment they were getting.
How up to date is this evidence?
The evidence is up-to-date to 13th October 2025.
Read the full abstract
Objectives
To assess the benefits and harms of high-intensity interval training (HIIT) on cardiometabolic health in healthy, sedentary adults.
Search strategy
We searched CENTRAL, MEDLINE, Embase, Web of Science Core Collection (SCI-Expanded, SSCi, CPCI-S), and two trial registries up to 13 October 2025.
Authors' conclusions
Compared with a non-exercise control, HIIT likely increases cardiorespiratory fitness and reduces waist circumference slightly, but we found no clear difference for systolic blood pressure, waist-to-hip ratio, or circulating triglycerides. The certainty of the evidence is low for circulating triglycerides and very low for systolic blood pressure, precluding firm conclusions.
Compared with MICT, HIIT may increase cardiorespiratory fitness slightly, but we found no clear difference for systolic blood pressure, waist circumference, waist-to-hip ratio, or circulating triglycerides. The certainty of the evidence is low for cardiorespiratory fitness, systolic blood pressure, and circulating triglycerides, precluding firm conclusions.
No studies in either comparison reported all-cause mortality. There were no reports of adverse events, and we are unsure if the studies actively monitored for them.
Our analysis included many studies, but all had relatively few participants. The evidence suggests that HIIT may be an effective alternative to MICT for sedentary populations at risk of cardiometabolic disease.
There is a need for larger, higher-quality RCTs with longer follow-up to determine the long-term efficacy and effectiveness of HIIT. Future studies should investigate the feasibility and safety of unsupervised HIIT, as all studies included in this review examined supervised HIIT interventions.
Funding
This Cochrane review was funded (in part) by the National Institute of Health Research (NIHR) and the Foreign, Commonwealth and Development Office (FCDO).
Registration
The protocol for this Cochrane review was published in the Cochrane Library in May 2020 and is available via 10.1002/14651858.CD013617.
