The Effectiveness of Low-frequency High-Intensity Interval Training (HIIT) in Overweight or Obese Young Adults

Individuals who fulfilled the following inclusion criteria were invited to participate in the present study: 1) Chinese male; 2) aged 18-30 years; and 3) overweight or obesity, defined as BMI ≥23 kg/m2 (classification of overweight for Hong Kong adults according to Department of Health, Hong Kong SAR Government) (13). Subjects were excluded if they had: 1) chronic medical and health condition such as cardiovascular diseases, diabetes, neurological disease, musculoskeletal disorder, cancers, and autoimmune diseases; 2) hypertension (blood pressure >140/90 mmHg); 3) contraindications to participating in physical exercise; 4) any pre-existing medical or physical issues that affected the experimental test; 5) physically active (i.e., >3 hours of moderate-intensity exercise weekly) or 6) lean overweight population (BMI ≥23 kg/m2, but percent body fat ≤20%) according to the BMI data corresponding to bioelectrical impedance estimated percent body fat cut-off value among Hong Kong Chinese adults.

Of those who were screened, 103 Chinese young adults were eligible to participate in this study. They were provided with written and verbal information on the study protocol and the possible associated discomforts and risks followed by obtaining their written informed consent to participate in this study. The study protocol and consent form were approved by the Human Subjects Ethics Sub-Committee of The Hong Kong Polytechnic University (ethics approval reference number: HSEARS20160927005-01).

This study was a single-blind, randomized, controlled trial. Subjects were randomly assigned to 1) no-intervention control (CON), 2) MICT performed thrice weekly (MICTx3/wk), 3) HIIT performed thrice weekly (HIITx3/wk), 4) twice weekly (HIITx2/wk), and 5) once weekly (HIITx1/wk). All subjects were instructed to maintain their usual daily activities. Outcome measures including aerobic capacity, body composition, blood pressure, resting heart rate, endothelial function, arterial stiffness, fasting glucose, lipids markers, adipokine marker, and inflammatory marker were assessed at baseline, 4 weeks and 8 weeks after the intervention.