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High-Intensity Interval Training decreases risk factors of chronic disease in people with overweight or obesity

Batacan RB Jr, Duncan MJ, Dalbo VJ et al. Effects of high-intensity interval training on cardiometabolic health: A systematic review and meta-analysis of intervention studies Br J Sports Med. 2017;51:494-503.

Review question

Does high-intensity interval training improve markers of health linked to heart disease and other chronic diseases?

Background

Physical activity is important for maintaining and improving health. Current health guidelines recommend moderate-vigorous exercise between 75 to 150 minutes per week, but many people have difficulty finding the time to do so. Interestingly, some recent research has shown that shorter periods of high-intensity interval training (HIIT) may be just as beneficial as longer periods of less intense exercise. HIIT involves alternating short bursts of high-intensity (very vigorous) exercise with low-intensity exercise or rest. This review measured whether HIIT can effectively decrease risk factors for heart disease and other chronic diseases, such as diabetes.

How the review was done

This is a review of 65 studies conducted from 2004 to 2015. Some of these studies were combined in a meta-analysis. Most studies were of low to fair quality.

• All participants were adults, most between the ages of 18 and 35. Many of the studies only included people with medical conditions such as high blood pressure, heart disease, diabetes, overweight or obesity.
• Study participants were involved in HIIT exercise programs, which ranged from a single session to a year-long program of three sessions per week. Programs involved different types of exercise, such as treadmill running, swimming and cycling.
• Researchers measured various markers of risk for chronic disease. These included VO₂ max (a measure of fitness), resting heart rate, blood pressure, body weight, body mass index, body fat, waist and hip circumference, blood sugar, insulin, cholesterol and blood markers of inflammation.
• In some studies, results were compared to control groups who did not participate in the HIIT programs.

What the researchers found

Participants in the HIIT exercise programs increased their fitness levels. In addition, after less than 12 weeks of HIIT, people with overweight or obesity saw improvements in their waist circumference, diastolic blood pressure and blood sugar. People who participated in the HIIT programs for 12 or more weeks also showed improvements in systolic blood pressure, body fat and resting heart rate. Decreases in blood sugar were not maintained after 12 weeks. More research is needed to understand if HIIT can further benefit people without overweight or obesity, beyond what was found in this review.

Conclusion

HIIT appears to be an effective way to decrease risk factors for chronic disease, particularly in people with overweight or obesity. HIIT is most effective when performed at least three times a week for 12 or more weeks.