Summary: In a randomised trial in people at higher risk of gestational diabetes, combining time-restricted eating with exercise from before conception through pregnancy did not significantly improve glucose tolerance in late pregnancy, with adherence falling as pregnancy progressed.
PICO Summary
| Element | Detail |
|---|---|
| Population | 167 participants with at least one gestational-diabetes risk factor contemplating pregnancy (111 became pregnant); single-centre, Norway. |
| Intervention | Exercise training (≥100 weekly PAI points) plus time-restricted eating (≤10 h/day, ≥5 days/week), started before pregnancy and continued throughout. |
| Comparison | Standard care. |
| Outcome | No significant effect on 2-hour plasma glucose at gestational week 28 (mean difference 0.48 mmol/L; 95% CI -0.05 to 1.01; p=0.08). Prepregnancy adherence was modest (about 37–44%) and fell during pregnancy. |
BEFORE THE BEGINNING Trial
RCT · gestational diabetes risk · to week 28
Time-restricted eating plus exercise from before conception did not significantly improve 2-hour glucose at week 28. Adherence was modest and fell during pregnancy.
Expert Commentary
This is a well-designed, important negative trial, and its publication in a major journal reflects how much we need clear null results in this field. The premise was genuinely clever, start the lifestyle intervention before conception to establish metabolic improvements ahead of the insulin resistance that pregnancy imposes, rather than intervening too late. That this still did not significantly improve late-pregnancy glucose tolerance is informative on two levels. It tells us that timing alone does not crack the problem, and it echoes earlier lifestyle-prevention trials such as UPBEAT and LIMIT that also failed to reduce gestational diabetes, suggesting the placental-hormone-driven physiology may be relatively resistant to behavioural modification. The obvious confounder is adherence, which was modest before pregnancy and declined further during it, so this is partly a test of a realistic programme rather than the concept under perfect compliance. Reassuringly, no harm was seen. Can I use this with my patients? Yes, to set honest expectations. I would not present time-restricted eating as an evidence-based way to prevent gestational diabetes, while still encouraging healthy weight, balanced eating, and activity for their broader benefits, and ensuring timely screening when risk is high.
References
Sujan MJ, Skarstad HMS, Rosvold G, et al. 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). BMJ. 2025;390:e083398. doi:10.1136/bmj-2024-083398