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

Abstract

Objective: To determine the effect of a prepregnancy lifestyle intervention on glucose tolerance in people at higher risk of gestational diabetes mellitus.

Design: Single centre randomised controlled trial (BEFORE THE BEGINNING).

Setting: University hospital in Trondheim, Norway.

Participants: 167 participants with at least one risk factor for gestational diabetes mellitus who contemplated pregnancy.

Intervention: The 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 before 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 for at least five days a week.

Main outcome measures: Two hour plasma glucose level in an oral glucose tolerance test at gestational week 28. The primary analysis used an intention-to-treat principle.

Results: 167 participants were enrolled from 2 October 2020 to 12 May 2023: 84 in the intervention group and 83 in the control group, out of whom 111 became pregnant (56 in intervention group and 55 in control group). One participant in the intervention group was excluded from the analysis because of prepregnancy diabetes. Pregnancy data from one participant in the control group were excluded from the analysis because of twin pregnancy. The intervention had no significant effect on two hour plasma glucose level in an oral glucose tolerance test at gestational week 28 (mean difference 0.48 mmol/L, 95% confidence interval -0.05 to 1.01, P=0.08). In the prepregnancy period, 31/83 participants (37%) in the intervention group adhered to prespecified criteria, whereas 24/55 participants (44%) in the intervention group who became pregnant fulfilled these criteria. During the prepregnancy period, the average eating window was 9.9 hours/day (standard deviation 1.2) and the average number of weekly PAI points was 111 (standard deviation 54), but the adherence to both intervention components decreased during pregnancy.

Conclusions: A combination of time restricted eating and exercise training started before and continued throughout pregnancy had no significant effect on glycaemic control in late pregnancy.

Trial registration: ClinicalTrials.gov NCT04585581.

Fig 1

Study design. After baseline assessments, participants were randomly allocated (1:1) to lifestyle intervention or standard care control group. Intervention consisted of exercise training and time restricted eating, started before pregnancy and continued throughout pregnancy. Amount of exercise was set using heart rate based physical activity metric (personal activity intelligence, PAI), with goal of ≥100 weekly PAI points. Time restricted eating involved consuming all energy within ≤10 hours/day for at least five days a week. Further assessments were performed eight weeks after baseline in prepregnancy period, and at gestational weeks 12 and 28. Pregnancy and birth outcomes were collected from hospital records after delivery. Neonatal outcomes were assessed within 72 hours after birth and 6-8 weeks after birth

Fig 2

Flowchart of participants. *Participants who did not conceive within specified time were excluded from further participation in trial, but their prepregnancy data were included

Fig 3

Blood glucose two hours after ingestion of 75 g glucose in oral glucose tolerance test at gestational weeks 12 and 28 according to group. Data are observed means and standard deviations for intention-to-treat population. P value calculated for between group differences using linear mixed model

Fig 4

Adherence to intervention. Upper panel: time window of energy intake during baseline week, prepregnancy period, and first, second, and third trimesters of pregnancy according to group. Vertical lines represent daily duration of energy intake, with ends indicating means of time of first and last energy intake for intention-to-treat population. P values calculated for between group differences in window of energy intake using linear mixed model. Lower panel: physical activity intelligence (PAI) points earned for each rolling week during baseline week, prepregnancy period, and first, second, and third trimesters of pregnancy in intervention group. Bars show mean PAI points per week, error bars show standard deviation, and symbols show individual data. P values calculated for within group differences from baseline estimated by linear mixed model