Isolated and combined effects of high-intensity interval training and time-restricted eating on glycaemic control in reproductive-aged women with overweight or obesity: study protocol for a four-armed randomised controlled trial

INTRODUCTION: Overweight and obesity in reproductive-aged women is a global problem due to the increased risk of subfertility, pregnancy complications and cardiometabolic diseases. High-intensity interval training and time-restricted eating are two primary lifestyle interventions that, independently, have positive effects on a range of health outcomes. Whether these two strategies have synergistic effects is currently unknown. Our primary aim is to determine the isolated and combined effect of high-intensity interval training and time-restricted eating on glycaemic control in reproductive-aged women with overweight/obesity. METHODS AND ANALYSIS: The study is a randomised controlled trial with four parallel groups. Women (N=120) aged 18–45 years with body mass index ≥27 kg/m(2) will be randomly allocated (1:1:1:1) to either: (1) high-intensity interval training, (2) time-restricted eating, (3) a combination of high-intensity interval training and of time-restricted eating, or (4) a control group. The duration of each intervention will be 7 weeks. The primary outcome measure will be glycaemic control, determined by the total area under the plasma glucose curve over 2 hours after a 75-gram oral glucose tolerance test. Secondary outcome measurements will include markers of cardiovascular and metabolic health (peak oxygen uptake, blood pressure, blood lipids, body composition, insulin sensitivity), sleep quality, physical activity, diet and adherence rates to the intervention. ETHICS AND DISSEMINATION: The Regional Committee Medical Research Ethics, Norway has approved the trial protocol. This study will provide important new knowledge to both the scientific community and the general population about the isolated and combined effects of two novel diet–exercise strategies on cardiovascular and metabolic health among women with overweight/obesity. TRIAL REGISTRATION NUMBER: NCT04019860.