Background:
Regular moderate-intensity exercise provides many health benefits, but adherence is often poor. An alternative approach - high-intensity interval training (HIIT), has demonstrated similar or better effectiveness over the short-term in supervised laboratory settings. Whether overweight people are able to undertake HIIT in the real-world without supervision, especially over the long-term, is unknown. The aim of this study was to determine the long-term adherence and effectiveness of an unsupervised HIIT programme in overweight and obese adults.
Methods:
Within a weight loss intervention study, 250 overweight adults (BMI>27) opted to undertake either HIIT (n=104, 42%), or current guidelines of at least 30 minutes daily moderate-intensity exercise (n=146, 58%). Following a single training session, HIIT participants were advised to undertake HIIT sessions independently thrice weekly for 12 months.
Results:
Those who chose HIIT were not younger, leaner, fitter or more active than those choosing current recommendations at baseline. At 12 months, the choice to undertake HIIT as an alternative to standard exercise guidelines led to no significant differences in any health outcomes: differences (95% CI) were -0.44kg (-2.5kg, 1.6kg) for weight, -103cm3 (-256cm3, 49cm3) for visceral fat, 0.0 ml/kg/min (-1.3, 1.2ml/kg/min) for estimated VO2max and 12 counts per minute (-26, 49) for overall physical activity. However, HIIT participants did report significantly higher enjoyment of physical activity (2.5: 0.6, 4.3). Although adherence to HIIT protocols was poor, those who continued with HIIT to 12 months (23%) had significantly greater weight loss (-2.7kg: -5.2kg, -0.2kg) and reductions in visceral fat (-292cm3: -483cm3, -101cm3) than non-adherent participants.
Conclusion:
Many overweight individuals of all backgrounds will try HIIT as an alternative to current exercise recommendations. HIIT did not perform better than current guidelines in the real world, presumably due to considerable non-adherence. However, important reductions in weight and visceral fat are feasible with good adherence.