A higher-carbohydrate, lower-fat diet reduces free fatty acids in the blood by 20% compared to a low-carb, high-fat diet in pregnant women with gestational diabetes, according to a 2026 randomized controlled trial of 23 women per group published in the American Journal of Clinical Nutrition. Both diets controlled blood sugar effectively, but the higher-carb approach produced more stable fat metabolism after meals, which may benefit fetal development.
A new study compared two different eating plans for pregnant women with gestational diabetes. One plan focused on complex carbohydrates with less fat, while the other was a traditional low-carb, higher-fat approach. Researchers found that the higher-carb, lower-fat diet led to lower levels of free fatty acids in the blood after meals, which could be better for both mom and baby. Both diets kept blood sugar under control, but they affected the body’s fat metabolism differently. This research suggests that the type of carbohydrates and fat in a pregnant woman’s diet matters just as much as the total amount.
Key Statistics
A 2026 randomized controlled trial of 46 pregnant women with gestational diabetes found that a higher-carbohydrate diet (60% carbs, 25% fat) reduced free fatty acids by 20% compared to a low-carbohydrate diet (40% carbs, 45% fat) when measured at 36 to 37 weeks of pregnancy.
Women following a low-carbohydrate, high-fat diet showed a 20% increase in triglycerides and 15% increase in glycerol after eating, while women on a higher-carbohydrate diet had only a 14% increase in triglycerides and no change in glycerol, according to the 2026 American Journal of Clinical Nutrition study.
Both diet approaches achieved clinically acceptable blood sugar control in gestational diabetes, though the low-carb group had 12% lower glucose levels after meals, demonstrating that carbohydrate quality may matter more than quantity for metabolic health in pregnancy.
Birth weight and newborn body fat were similar between the higher-carb and low-carb diet groups in the 2026 trial, suggesting that reducing free fatty acid exposure through diet composition doesn’t compromise fetal growth.
The Quick Take
- What they studied: Whether eating more complex carbohydrates and less fat helps pregnant women with gestational diabetes better control the fatty substances in their blood after meals
- Who participated: 46 pregnant women diagnosed with gestational diabetes around 28 to 30 weeks of pregnancy. The study included 23 women in each diet group, all with similar starting weights (average BMI of 32)
- Key finding: Women eating the higher-carb, lower-fat diet had 20% less free fatty acids in their blood after eating breakfast compared to women on the low-carb, higher-fat diet. This difference was measured at 36 to 37 weeks of pregnancy
- What it means for you: If you have gestational diabetes, choosing complex carbohydrates and limiting fat may help reduce harmful fatty substances in your blood that could affect your baby’s development. However, talk with your doctor or dietitian before making major diet changes, as individual needs vary
The Research Details
This was a randomized controlled trial, which is one of the strongest types of research studies. Researchers divided 59 pregnant women with gestational diabetes into two groups. One group ate a diet with 60% of calories from carbohydrates and 25% from fat (called the CHOICE diet). The other group ate a traditional low-carbohydrate diet with 40% carbs and 45% fat (called LC/CONV). All meals were provided by the researchers to ensure accuracy. The women followed their assigned diet for about 7 to 8 weeks, starting after their gestational diabetes diagnosis around 28 to 30 weeks of pregnancy.
At two time points (30 to 31 weeks and 36 to 37 weeks), researchers gave each woman a test breakfast containing 30% of her daily calories. They then took blood samples every hour for 5 hours to measure glucose, triglycerides (a type of fat), free fatty acids, and glycerol (a component of fat). Both diets contained the same amount of simple sugars (about 70 grams per day) and the same proportion of saturated fat (35% of total fat), so the main difference was the overall carbohydrate and fat content.
This design is important because it allowed researchers to isolate the effects of carbohydrate quality and fat intake while controlling other variables. By providing all meals, they ensured women actually followed the diets as planned, making the results more reliable than studies where people choose their own foods.
Understanding how different diets affect the fatty substances in a pregnant woman’s blood is crucial because these substances can cross the placenta and affect fetal development. High levels of free fatty acids and triglycerides may increase insulin resistance (when the body doesn’t respond well to insulin) and contribute to excessive fat storage in the developing baby. This research approach matters because it measures what actually happens in the blood after eating, not just blood sugar levels alone. Previous studies focused mainly on glucose control, but this trial examined the complete metabolic picture
This study has several strengths: it was randomized (reducing bias), controlled (all meals provided), and measured multiple important markers of metabolism. However, the final sample size was smaller than originally planned (23 per group instead of the intended larger number), which means results should be interpreted with some caution. The study was conducted at a single medical center, so results may not apply equally to all populations. The relatively short duration (7 to 8 weeks) means we don’t know if benefits would continue longer. Despite these limitations, this is one of the first rigorous trials to directly compare these diet approaches in gestational diabetes
What the Results Show
The main finding was striking: women on the CHOICE diet (higher carbs, lower fat) had 20% lower free fatty acids in their blood after eating breakfast at 36 to 37 weeks of pregnancy compared to women on the LC/CONV diet. This difference was statistically significant, meaning it was unlikely to occur by chance. Interestingly, both diets successfully controlled blood sugar, though the LC/CONV group had slightly lower glucose levels after the test meal (12% lower). However, this small difference in glucose control didn’t translate to better overall outcomes.
When researchers looked at triglycerides and glycerol (another fat-related marker), they found an unexpected pattern. Women on the LC/CONV diet showed larger increases in both triglycerides (20% increase) and glycerol (15% increase) after eating. Women on the CHOICE diet had a smaller increase in triglycerides (14% increase) and no change in glycerol. This suggests that the lower-fat, higher-carb approach produced a more stable fat metabolism after meals.
Baby outcomes were similar between groups: birth weight and newborn body fat were comparable, and maternal weight gain during pregnancy was the same. This is reassuring because it shows that the CHOICE diet didn’t cause any negative effects on fetal growth despite the different nutrient composition.
The study measured several secondary outcomes that provide additional context. Both diets were eucaloric, meaning they contained the same total calories, so weight gain differences weren’t due to eating more or less overall. The researchers carefully controlled simple sugar intake (70 grams per day in both diets) and saturated fat proportion (35% of total fat in both diets), ensuring that differences in outcomes were truly due to carbohydrate quality and total fat content. The fact that these variables were controlled strengthens confidence in the results. The researchers also noted that glycemic control remained clinically acceptable in both groups, meaning blood sugar stayed in safe ranges for pregnancy despite the different approaches
This research fills an important gap in the literature. Previous studies on gestational diabetes focused primarily on blood glucose control, but few rigorous trials examined how different diets affect free fatty acids and triglycerides, the substances that cross the placenta and may influence fetal fat development. Some older research suggested that low-carbohydrate diets might be beneficial for gestational diabetes, but this trial provides evidence that the quality of carbohydrates and the amount of fat matter significantly. The findings align with emerging research showing that not all low-carb diets produce the same metabolic effects, and that the type of carbohydrate (complex versus simple) influences how the body processes fats
Several limitations should be considered when interpreting these results. First, the final sample size was smaller than originally planned (46 women instead of a larger target), which reduces statistical power. Second, the study lasted only 7 to 8 weeks, so we don’t know if these benefits persist throughout pregnancy or after delivery. Third, the study was conducted at a single medical center, so results may not apply equally to all ethnic groups or populations. Fourth, researchers measured blood markers at only two time points, so they couldn’t track changes over the entire pregnancy. Finally, while the CHOICE diet produced lower free fatty acids, the clinical significance of a 20% reduction isn’t yet fully understood in terms of long-term baby health outcomes
The Bottom Line
For pregnant women with gestational diabetes, Gram Research analysis suggests choosing complex carbohydrates (whole grains, vegetables, legumes) over refined carbohydrates and limiting total fat intake may help reduce harmful fatty substances in the blood. This approach appears to work as well as low-carb diets for blood sugar control while producing more favorable fat metabolism. Confidence level: Moderate. These findings are promising but come from a single study with a modest sample size. Work closely with your healthcare provider or registered dietitian to develop a personalized meal plan, as individual needs vary based on weight, activity level, and other health factors
This research is most relevant for pregnant women diagnosed with gestational diabetes who are deciding between different dietary approaches. It may also interest healthcare providers managing gestational diabetes and researchers studying fetal development. Women without gestational diabetes should not assume these findings apply to them, as pregnancy diabetes involves different metabolic challenges. Men and non-pregnant individuals should not apply these recommendations, as pregnancy creates unique nutritional needs
The study measured changes after 7 to 8 weeks of following the diet, so improvements in blood fat levels may appear within weeks of starting a higher-carb, lower-fat approach. However, the most significant differences were observed at 36 to 37 weeks of pregnancy, suggesting that sustained adherence over several weeks produces the best results. Long-term benefits for baby health may take months or years to fully understand
Frequently Asked Questions
Is a low-carb diet better for gestational diabetes than a high-carb diet?
Not necessarily. A 2026 trial found that a higher-carb, lower-fat diet reduced harmful free fatty acids by 20% while controlling blood sugar just as well as a low-carb approach. The quality of carbohydrates and amount of fat may matter more than total carbs for pregnant women with gestational diabetes.
What happens to free fatty acids when you eat a low-carb diet during pregnancy?
Free fatty acids increase more on low-carb, high-fat diets. In a 2026 study, women on a low-carb diet had 20% higher free fatty acids after meals compared to those eating more complex carbohydrates. These fatty substances cross the placenta and may affect fetal fat development.
Can I safely eat complex carbohydrates if I have gestational diabetes?
Yes. Research shows that complex carbohydrates (whole grains, beans, vegetables) can be part of an effective gestational diabetes diet. A 2026 trial found that 60% of calories from carbohydrates maintained good blood sugar control while improving fat metabolism compared to lower-carb approaches.
How long does it take to see benefits from changing my diet in gestational diabetes?
Changes in blood fat levels may appear within weeks. The 2026 study measured significant differences after 7 to 8 weeks of following a higher-carb, lower-fat diet, with the most pronounced effects observed at 36 to 37 weeks of pregnancy.
Will eating more carbs make my baby heavier if I have gestational diabetes?
No. A 2026 randomized trial found that birth weight and newborn body fat were similar between women eating higher-carb diets and those eating low-carb diets, despite the different carbohydrate amounts. Diet composition affected fat metabolism without affecting baby size.
Want to Apply This Research?
- Track daily carbohydrate sources by type (complex carbs like whole grains versus simple carbs like sugar) and total fat intake in grams. Log these alongside blood glucose readings to see how different carbohydrate quality affects your personal glucose patterns
- Replace refined carbohydrates with complex carbohydrates at each meal: choose whole grain bread instead of white bread, brown rice instead of white rice, and add beans or lentils to meals. Reduce visible fats by using cooking spray instead of oil, choosing lean proteins, and limiting added oils and butter
- Weekly review of carbohydrate quality ratio (percentage of carbs from whole foods versus processed sources) and fat intake trends. Compare these patterns with blood glucose readings and energy levels to identify which combinations work best for your individual metabolism
This article summarizes research findings and should not replace professional medical advice. Gestational diabetes requires individualized medical management. Before making any dietary changes during pregnancy, consult your obstetrician, midwife, or registered dietitian who specializes in pregnancy nutrition. This research comes from a single trial with a modest sample size; larger studies may provide additional insights. All pregnant women with gestational diabetes should receive regular blood sugar monitoring and prenatal care from qualified healthcare providers.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.