Impact of fat and protein on postprandial glycemia in gestational diabetes: A randomized pilot crossover trial.

BACKGROUND: The first-line treatment for gestational diabetes mellitus (GDM) is dietary modification, but there is little evidence on the impact of fat and protein on glycemia in pregnancy. OBJECTIVE: To examine the effect of fat and protein on postprandial glycemia in individuals with GDM and to determine if this response differed in GDM characterized by insulin resistance versus insulin deficiency. METHODS: We conducted a double-blind randomized crossover pilot study using test meals with similar caloric (390-411 kcal) and carbohydrate content (45%), but with either high-fat (41%) or high-protein (35%) content in diet-controlled GDM (N = 16). We used fasting glucose and insulin levels to classify participants as insulin-resistant or insulin-deficient GDM. The primary outcome was peak postprandial glucose within 3 h following the test meals measured by a continuous glucose monitor (CGM). Secondary outcomes included glucose area under the curve (AUC) and glycemic excursion (peak postprandial glucose minus pre-meal glucose). We used t-tests to evaluate the relationship between meal type and outcomes. RESULTS: The high-fat meal resulted in a higher mean (standard deviation [SD]) peak postprandial glucose (146.4 [19.7] mg/dL) than the high-protein meal (137.2 [21.1] mg/dL, p = 0.03) (mean difference, 9.2 [15.9] mg/dL; 95% confidence interval [CI], 0.78, 148.4). The glucose AUC (high fat: 26,236 [3220] mg/dL*min, high protein: 24,788 [3567] mg/dL*min, p = 0.03) (mean difference, 1448 [2462] mg/dL*min; 95% CI, 136.0, 2760) and the glycemic excursion (high fat: 68.3 [23.3] mg/dL, high protein: 59.7 [22.3] mg/dL, p = 0.03) (mean difference, 8.6 [14.9] mg/dL; 95% CI, 0.7, 16.5) were higher after the high-fat meal. There was no differential peak postprandial glucose response to high-fat versus high-protein in insulin-deficient versus insulin-resistant GDM (mean difference, -0.25 mg/dL; 95% CI, -24.1, 23.5, p = 0.98). CONCLUSION: In GDM, a high-protein meal leads to lower CGM-measured postprandial glucose compared to a high-fat meal, when calories and carbohydrate content are held constant. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT04187521.