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Keywords:

  • GDM;
  • diet;
  • carbohydrate

Paper Presentation

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  2. Paper Presentation

Objective

The historic practice of advising a low-carbohydrate and higher fat diet in the management of gestational diabetes mellitus has not been sufficiently tested. In addition to glucose, high maternal triglycerides and free fatty acids are independent risk factors for fetal macrosomia and excess neonatal adiposity. We tested the hypothesis that a higher complex carbohydrate/lower fat diet would result in higher postprandial glucose excursions but an overall 24-hour glucose area-under-the-curve resulted that is no different or lower than that of a low-carbohydrate/higher fat diet.

Design

Randomized crossover study.

Setting

Clinical Translational Research Center.

Patients/Participants

Women with diet-controlled gestational diabetes mellitus.

Methods

Women with diet-controlled gestational diabetes mellitus consumed a high complex carbohydrate/ low-fat diet (HC/LF; 60% CHO, 25% fat, and 15% protein) and a low carbohydrate/higher fat diet (LC/HF; 40% carbohydrate [CHO], 45% fat, and 15% protein) for 3 days each (washout in between) while wearing a continuous glucose monitor. On day four of each diet, postprandial lipemia was measured hourly for 5 hours after women consumed breakfast (30% of total daily calories). All food was provided by the Clinical Translational Research Center. A paired t test was used for difference testing.

Results

Ten women with gestational diabetes mellitus (Mean ± SEM; body mass index 33.6 ± 1.5 kg/m2; age 29 ± 1 years; 30.4 ± 0.5 weeks gestation) completed the diet crossover. Whereas continuous glucose monitor revealed no difference in mean nocturnal blood glucose (BG) or fasting BG (p > .05), the HC/LF diet yielded a modestly higher level: mean 24-hour BG (96.3 ± 3.4 vs. 90.3 ± 3.8 mg/dl, p = .03, respectively), mean 24-hour area-under-the-curve, and mean postprandial 2-hour area-under-the-curve across meals (p < .005). One- and two-hour postprandial glucose by continuous glucose monitor were higher across meals on the HC/LF diet compared to the LC/HF diet (115 ± 3 vs. 106 ± 3 mg/dl [p = .009] and 108 ± 5 vs. 98 ± 3 mg/dl [p = .01], respectively). On day four, there were no differences in fasting plasma glucose, insulin, triglycerides, or free fatty acids. Postprandial blood analyses revealed higher 5-hour area-under-the-curve for glucose and insulin on the HC/LF diet (p = .004 for both), no difference in the 5-hour triglycerides area-under-the-curve, but a higher 5-hour free fatty acids area-under-the-curve on the HF/LC diet (p = .005).

Conclusion/Implications for Nursing Practice

The pattern of glycemia on both diets was remarkably similar. Despite modestly higher glucose concentrations on the HC/LF diet, both diets easily met current recommendations (<140 and <120 mg/dl at 1 and 2 hours postprandial; mean BG 87-104 mg/dl). Thus, nurses may be able to help women with gestational diabetes mellitus consume a more balanced diet (in carbohydrate/fat) while still meeting glycemic targets. The consistently higher free fatty acids on the LC/HF diet could worsen maternal insulin resistance and augment neonatal adiposity. Further investigation is required to understand the importance of balancing dietary carbohydrate and fat by its metabolic effects on mother and offspring.