Time-restricted eating and exercise training before and during pregnancy for people with increased risk of gestational diabetes: the BEFORE THE BEGINNING randomised controlled trial

ObjectiveTo determine the effect of a pre-pregnancy lifestyle intervention on glucose tolerance in people at higher risk of gestational diabetes mellitus (GDM). DesignRandomised controlled trial. SettingUniversity hospital in Trondheim, Norway. Participants167 people with at least one risk factor for GDM who contemplated pregnancy. InterventionThe participants were randomly allocated (1:1) to a lifestyle intervention or a standard care control group. The intervention consisted of exercise training and time-restricted eating, started pre-pregnancy and continued throughout pregnancy. Exercise volume was set using a physical activity metric that translates heart rate into a score (Personal Activity Intelligence, PAI), with the goal of [≥] 100 weekly PAI-points. Time-restricted eating involved consuming all energy within [≤] 10 hours/day, [≥] 5 days per week. Main outcome measures2-hour plasma glucose level in an oral glucose tolerance test (OGTT) in gestational week 28. The primary analysis used an intention-to-treat principle. ResultsFrom 02.10.2020 to 12.05.2023, we included 167 participants: 84 in intervention and 83 in control, out of whom 111 became pregnant (56 in intervention and 55 in control). One participant in the intervention group was excluded from the analysis because of pre-pregnancy diabetes. Pregnancy data from one participant in the control group were excluded from the analysis because of twin pregnancy. Time to pregnancy was 112 days (SD 105) in the intervention (INT) group and 83 days (SD 69) in the control (CON) group (p = .087). The intervention had no significant effect on 2-hour plasma glucose level in an OGTT in gestational week 28 (mean difference, 0.48 mmol/L, 95% confidence interval [CI], -0.05 to 1.01, p = .077). There was no evidence of between-group differences in other measures of glycaemic control before or during pregnancy. The intervention did not significantly influence GDM prevalence rates in gestational week 12 (INT 5.5%, CON 5.6%, p = 1.000) or gestational week 28 (INT 14.5%, CON 11.1%, p = .592). In gestational week 28, the intervention group had gained less weight (2.0 kg, 95% CI, -3.3 to -0.8, p = .002) and fat mass (-1.5 kg, 95% CI, -2.5 to -0.4, p = .008) than the control group. Participants could adhere to the [≤] 10-hour eating window and maintain [≥] 100 PAI per rolling week pre-pregnancy, but adherence to both intervention components decreased during pregnancy. ConclusionsA combination of time-restricted eating and exercise training started before and continued throughout pregnancy had no significant effect on glycaemic control in late pregnancy, but our findings suggest that the intervention lowered gestational weight and fat mass gain in people with increased risk of GDM. Trial registrationClinicalTrials.gov NCT04585581