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The original nutrition approach for the treatment of gestational diabetes mellitus (GDM) was to reduce total carbohydrate intake to 33-40% of total energy (EI) to decrease fetal overgrowth. Conversely, accumulating evidence suggests that higher carbohydrate intakes (60-70% EI, higher quality carbohydrates with low glycemic index/low added sugars) can control maternal glycemia. The Institute of Medicine (IOM) recommends ≥175 g/d of carbohydrate intake during pregnancy; however, many women are consuming lower carbohydrate (LC) diets (<175 g/d of carbohydrate or <40% of EI) within pregnancy and the periconceptual period aiming to improve glycemic control and pregnancy outcomes. This report systematically evaluates recent data (2018-2020) to identify the LC threshold in pregnancy in relation to safety considerations. Evidence from 11 reports suggests an optimal carbohydrate range of 47-70% EI supports normal fetal growth; higher than the conventionally recognized LC threshold. However, inadequate total maternal EI, which independently slows fetal growth was a frequent confounder across studies. Effects of a carbohydrate intake <175 g/d on maternal ketonemia and plasma triglyceride/free fatty acid concentrations remain unclear. A recent randomized controlled trial (RCT) suggests a higher risk for micronutrient deficiency with carbohydrate intake ≤165 g/d in GDM. Well-controlled prospective RCTs comparing LC (<165 g/d) and higher carbohydrate energy-balanced diets in pregnant women are clearly overdue.

Nutrition therapy provides the foundation for treatment of gestational diabetes (GDM), and has historically been based on restricting carbohydrate (CHO) intake. In this paper, randomized controlled trials (RCTs) are reviewed to assess the effects of both low- and higher CHO nutrition approaches in GDM. The prevailing pattern across the evidence underscores that although CHO restriction improves glycemia at least in the short-term, similar outcomes could be achievable using less restrictive approaches that may not exacerbate IR. The quality of existing studies is limited, in part due to dietary non-adherence and confounding effects of treatment with insulin or oral medication. Recent evidence suggests that modified nutritional manipulation in GDM from usual intake, including but not limited to CHO restriction, improves maternal glucose and lowers infant birthweight. This creates a platform for future studies to further clarify the impact of multiple nutritional patterns in GDM on both maternal and infant outcomes.

Objective: The conventional diet approach to gestational diabetes mellitus (GDM) advocates carbohydrate restriction, resulting in higher fat (HF), also a substrate for fetal fat accretion and associated with maternal insulin resistance. Consequently, there is no consensus about the ideal GDM diet. We hypothesized that, compared with a conventional, lower-carbohydrate/HF diet (40% carbohydrate/45% fat/15% protein), consumption of a higher-complex carbohydrate (HCC)/lower-fat (LF) Choosing Healthy Options in Carbohydrate Energy (CHOICE) diet (60/25/15%) would result in 24-h glucose area under the curve (AUC) profiles within therapeutic targets and lower postprandial lipids., Research Design and Methods: Using a randomized, crossover design, we provided 16 GDM women (BMI 34 ± 1 kg/m2) with two 3-day isocaloric diets at 31 ± 0.5 weeks (washout between diets) and performed continuous glucose monitoring. On day 4 of each diet, we determined postprandial (5 h) glucose, insulin, triglycerides (TGs), and free fatty acids (FFAs) following a controlled breakfast meal., Results: There were no between-diet differences for fasting or mean nocturnal glucose, but 24-h AUC was slightly higher (∼6%) on the HCC/LF CHOICE diet (P = 0.02). The continuous glucose monitoring system (CGMS) revealed modestly higher 1- and 2-h postprandial glucose on CHOICE (1 h, 115 ± 2 vs. 107 ± 3 mg/dL, P ≤ 0.01; 2 h, 106 ± 3 vs. 97 ± 3 mg/dL, P = 0.001) but well below current targets. After breakfast, 5-h glucose and insulin AUCs were slightly higher (P < 0.05), TG AUC was no different, but the FFA AUC was significantly lower (∼19%; P ≤ 0.01) on the CHOICE diet., Conclusions: This highly controlled study randomizing isocaloric diets and using a CGMS is the first to show that liberalizing complex carbohydrates and reducing fat still achieved glycemia below current treatment targets and lower postprandial FFAs. This diet strategy may have important implications for preventing macrosomia.

This study evaluated if the effect of dietary macronutrient composition on adipose tissue lipoprotein lipase (ATLPL) and skeletal muscle lipoprotein lipase (SMLPL) predicted the long-term (over 4 years) changes in body weight and composition in free-living adults. Using a crossover design, 39 healthy subjects (n = 24 normal weight, n = 7 overweight, n = 8 obese) each followed a 2-week isocaloric high-carbohydrate (HC; 55% CHO:25% fat) and high-fat (HF; 30% CHO:50% fat) diet. On day 15 of each diet, biopsies were performed in the fasted state and 6 h after a meal. Body weight and composition were measured annually over 4 years. The outcomes for body weight, fat mass and % body fat were assessed using a linear two-stage mixed model. The mean (±SEM) increase in body weight and fat mass over 4 years was 0.29 ± 0.15 kg/year (P = 0.063) and 0.31 ± 0.15 kg/year (P = 0.051), respectively. The most consistent predictors of future body weight and fat changes were the ΔATLPL and ΔSMLPL responses (0-6 h) to a HC diet/meal. For the HC diet/meal, the subjects who had an increase in ATLPL activity/cell gained more % body fat over 4 years (P = 0.006) whereas subjects who had a decrease in SMLPL activity/g also had an increase in fat mass (P = 0.021). No significant relationships were observed between fasting ATLPL and SMLPL or enzyme responses to meals and any of the outcomes following the HF diet. In free-living adults the variability in tissue-specific lipoprotein lipase (LPL) responsiveness to a HC diet/meal predicts longitudinal changes in body composition.

Background: The prevention and treatment of obesity is a public health challenge., Objective: We investigated the effects of dietary composition, insulin sensitivity (S(I)), and energy balance on predicted changes in body composition., Design: In a randomized crossover design study, 39 normal-weight (n = 23), overweight (n = 8), and obese (n = 8) men and women (aged 25-36 y) each followed a 15-d isocaloric high-fat (HF; 50% fat) and high-carbohydrate [HC; 55% carbohydrate (CHO)] diet with a 4-6-wk washout period during the first year. During each treatment, energy balance was measured while the subjects were inactive by using indirect calorimetry on day 15, and S(I) was measured by using a euglycemic clamp study (40 mU . m(-2) . min(-1)) on day 16. Weight and body composition were then measured annually for 4 y. The outcomes for fat mass, percentage body fat, and weight were measured by using a linear 2-stage mixed model., Results: CHO balance (day 15) and S(I) (day 16) on the HC diet were highly and significantly correlated (r = 0.55, P < 0.001). On the HC diet, the subjects who had a higher positive CHO balance (day 15) gained less fat mass (P < 0.001), percentage body fat (P = 0.006), and weight (P = 0.024) over time. When adjusted for S(I), CHO balance remained a significant predictor of changes in fat mass (P = 0.021) and percentage body fat (P = 0.025)., Conclusions: On a HC diet, the subjects who had a higher positive CHO balance on day 15 while they were inactive gained less fat mass during 4 y, a predictive effect independent of S(I). As suggested in rodents, the capacity to expand the glycogen pool might reduce energy intake and protect against fat and weight gain.