Metabolic Effects of Hypocaloric Diets in Management of Gestational Diabetes

Although hypocaloric diets have been advocated for the management of the obese gravida and the obese mother with gestational diabetes, there is no general agreement on how severely calories should be restricted or on how this therapeutic approach compares with insulin therapy. The lack of consensus is in part because of the lack of studies comparing insulin management with the effects of different degrees of hypocaloric feeding and its effects on metabolism and glycemic status. We review the effects of 50 and 33% calorie restriction on glycemic status and intermediary fuel status in obese gestational diabetic subjects and compare the results with the administration of 20 U NPH and 10 U regular insulin every morning, a therapy of proven value in reducing macrosomia in gestational diabetes. When the two calorie-restriction regimens were compared after a 9-h overnight fast, glycemic status improved 10–20% on both. Ketonuria increased about twofold with 50% calorie restriction, but on average no increase in ketonuria was seen on the 33% calorie-restriction regimen. Both calorie-restriction programs led to a reduction in levels of plasma triglyceride, a correlate of infant birth weight. In contrast, the insulin regimen diminished ketonuria, but glycemic status improved little, and plasma triglyceride concentrations did not decline. Although more studies are needed to confirm these trends, the beneficial effect of 33% calorie restriction, which occurred without marked ketonuria, is consistent with previous studies in gestational diabetes. In addition, the simultaneous improvements observed in plasma glucose and triglyceride concentrations suggest that moderate calorie restriction may be valuable in preventing macrosomia in the offspring of the obese subject with gestational diabetes. A clinical trial to test this hypothesis is warranted.