Accelerated starvation in late pregnancy: a comparison between obese women with and without gestational diabetes mellitus

We compared the glucose, insulin, free fatty acid, and 3-hydroxybutyrate responses to a briefly extended overnight fast during the third trimester of pregnancy between two groups: obese women with normal glucose tolerance (n = 10) and age- and weight-matched women with gestational diabetes mellitus (n = 10). After a 12-hour overnight fast, plasma glucose (95 +/- 4 vs. 78 +/- 2 mg/dl; p less than 0.01), insulin (32 +/- 5 vs. 17 +/- 2 microU/ml; p less than 0.02), and free fatty acid (860 +/- 63 vs. 639 +/- 79 mmol/L; p less than 0.05) levels were higher in the patients with gestational diabetes mellitus. 3-Hydroxybutyrate levels were similar in the two groups at that time (0.23 +/- 0.04 vs. 0.18 +/- 0.03 mmol/L; p greater than 0.3). When the fast was extended to 18 hours by having the patients skip breakfast, glucose levels fell more rapidly in the group with gestational diabetes mellitus but remained elevated compared with the nondiabetic women. Insulin levels declined at a similar rate in the two groups. Free fatty acid levels did not increase significantly in the group with gestational diabetes mellitus during the extended fast. In contrast, free fatty acid levels increased by 44% in the normal pregnant women, reaching the level observed in the group with gestational diabetes mellitus after 18 hours. 3-Hydroxybutyrate levels remained virtually identical in the two groups throughout the brief fast. Thus, compared with that of normal pregnant women, the response of obese women with gestational diabetes mellitus to brief caloric deprivation during late pregnancy was characterized by a greater fall in plasma glucose values without a greater propensity to ketosis. Our findings may have important implications for the dietary management of obese patients with gestational diabetes mellitus.