257-OR: ADA Presidents' Select Abstract: The Effect of a Reduced-Energy Diet upon Maternal Weight and Pregnancy Outcomes in Women with Gestational Diabetes—The DiGest Trial

Background: Reduced-energy diets improve clinical outcomes in type 2 diabetes but are untested in gestational diabetes.

Methods: In a randomized, controlled, double-blind, whole-diet replacement trial (ISRCTN; 37866), women with gestational diabetes and BMI <u>></u>25 kg/m² were assigned (1:1) to receive a standard-energy (2000 kcal/day) (control) or a reduced-energy diet (1200 kcal/day) (intervention) until delivery, provided as weekly dietboxes containing 40% carbohydrate, 35% fat and 25% protein. Diagnosis used the National Institute of Health and Care Excellence (NICE) and interim UK Covid-19 criteria. Primary outcomes were maternal weight change (enrolment to 36wks) and offspring standardized birthweight. Secondary outcomes included maternal glycemia, treatment requirements and neonatal outcomes.

Results: 423 women were randomized at 29wks gestation; (n=211 control; n=212 intervention). Outcome data were available for 386 (91.3%) participants at 36wks and 358 (84.6%) at delivery. Intervention and control groups had similar maternal weight change to 36wks (mean 0.41(SD 4.25) vs 0.50(4.15) kg; baseline-adjusted difference intervention vs control -0.148 (95%CI -0.95 to 0.68); p=0.741). The intervention reduced requirements for short-acting (odds ratio 0.37 (0.14 to 0.97); p=0.044) and long-acting (0.38 (0.19 to 0.75); p=0.006) insulin therapy at 36wks. Offspring had similar standardized birthweight (0.44(1.03) vs 0.44(0.85) SDS; 0.004(-0.20 to 0.19) p=0.967) and comparable rates of large-for-gestational-age and neonatal intensive care admission. Serious adverse events and withdrawals were similar between groups. Weight loss in late pregnancy appeared safe.

Conclusions: The protocol did not result in differences in weight gain or primary outcomes between groups but the provision of a reduced energy diet was associated with a reduced requirement for insulin therapy.