Effects of a preconception lifestyle intervention on cardiorespiratory fitness and glycaemic outcomes in people with increased risk of gestational diabetes: Secondary findings from the BEFORE THE BEGINNING randomised controlled trial

Objectives Obesity rates are rising globally, and many females of reproductive age are physically inactive, which negatively affect future maternal and neonatal health. In this secondary analysis, we determined the effect of a combined preconception lifestyle intervention on cardiorespiratory fitness and glycaemic outcomes after 7 weeks. Methods In the BEFORE THE BEGINNING randomised controlled trial, we randomised females who were at risk of gestational diabetes mellitus and planning pregnancy 1:1 to intervention or control. The intervention consisted of time-restricted eating (TRE) and exercise training and spanned from inclusion preconception throughout pregnancy. TRE involved restricting energy intake to ≤ 10-h/day on ≥ 5 days per week. Exercise volume was based on a heart-rate-based metric (Personal Activity Intelligence, PAI), with the goal of ≥ 100 weekly PAI-points. The main outcomes of interest in this secondary analysis were cardiorespiratory fitness and glycaemic outcomes after 7 weeks of intervention in the preconception period. Results Among 167 randomised participants, we included 166 in the intention-to-treat analysis. After 7 weeks of intervention, there was no between-group difference in relative VO2peak (0.8 mLkg-1min-1; 95% CI -0.2 to 1.9, P = 0.10) or glucose area under the curve (0.0 mmol/L; 95% confidence interval, CI -0.1 to 0.2, P = 0.76). Conclusion We found no evidence of effects of 7 weeks of combined TRE and exercise training on cardiorespiratory fitness or glycaemic outcomes in people with increased risk of gestational diabetes. Trial registration: ClinicalTrials.gov NCT04585581 .