Time-restricted eating and exercise training improve HbA1c and body composition in women with overweight/obesity: A randomized controlled trial.

Diet modification and exercise training are primary lifestyle strategies for obesity management, but poor adherence rates limit their effectiveness. Time-restricted eating (TRE) and high-intensity interval training (HIIT) improve cardiometabolic health in at-risk individuals, but whether these two interventions combined induce superior improvements in glycemic control than each individual intervention is not known. In this four-armed randomized controlled trial (ClinicalTrials.gov NCT04019860), we determined the isolated and combined effects of 7 weeks of TRE (≤10-h daily eating window, with ad libitum energy intake) and HIIT (three exercise sessions per week), compared with a non-intervention control group, on glycemic control and secondary cardiometabolic outcomes in 131 women (36.2 ± 6.2 years) with overweight/obesity. There were no statistically significant effects after isolated TRE, HIIT, or a combination (TREHIIT) on glucose area under the curve during an oral glucose tolerance test (the primary outcome) compared with the control group (TRE, -26.3 mmol/L; 95% confidence interval [CI], -82.3 to 29.7, p = 0.36; HIIT, -53.8 mmol/L; 95% CI, -109.2 to 1.6, p = 0.057; TREHIIT, -41.3 mmol/L; 95% CI, -96.4 to 13.8, p = 0.14). However, TREHIIT improved HbA1c and induced superior reductions in total and visceral fat mass compared with TRE and HIIT alone. High participant adherence rates suggest that TRE, HIIT, and a combination thereof may be realistic diet-exercise strategies for improving markers of metabolic health in women at risk of cardiometabolic disease.

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/m2 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.