A Diet Game-Changer

Research conducted by investigators at the University of Colorado College of Nursing and School of Medicine/Division of Endocrinology and Maternal-Fetal Medicine at Anschutz Medical Campus could pave the way for pregnancy nutrition guidelines across the world.

“Randomization to a Provided Higher-Complex-Carbohydrate Versus Conventional Diet in Gestational Diabetes Results in Similar Maternal 24-Hour Glycemia and Newborn Adiposity” was published in Diabetes Care, the American Diabetes Association journal, last month. CU Nursing Professor and Associate Dean of Research and Scholarship Teri Hernandez, PhD, RN, conducted the research with CU Medicine Professor of Medicine and Obstetrics/Gynecology Linda Barbour, MD, MSPH. Their research team included CU Nursing Lifestyle Grants and Contracts Program Manager Nicole Hirsch, MS, Senior Professional Research Assistant Emily Dunn, MS, RDN, CDE, Professional Research Assistant Kristy Rolloff, BS, and eight other medical professionals.

Pregnant women are usually diagnosed with gestational diabetes mellitus, or GDM, at the end of their second trimester. The Centers for Disease Control says there typically aren’t GDM symptoms. Someone’s medical history and risk factors might lead to a diagnosis. The CDC reports a woman’s blood sugar level usually returns to normal after a baby’s birth, but about half of women with GDM develop type 2 diabetes within 10 years of their pregnancy.

“(A GDM diagnosis) is usually a big shock,” Hernandez says. “Even if we as providers could have predicted which women could develop it, most women are very surprised.”

“One of the biggest complications of gestational diabetes is that the baby overgrows and is born too big with increased body fat. It sets them up for a lifetime of heightened risk for being overweight and having obesity,” she says. “So most of our intervention efforts in pregnancy try to normalize birthweight and prevent the development of excess fat stores.”

Changing Diets During Pregnancy

Nutrition therapy for GDM has typically focused on a low-carb diet. In this study, researchers tested the hypothesis that a diet with higher complex carbs and lower fats could improve maternal insulin resistance, and 24-hour glycemia, and prevent excess adipose tissue development in the infant.

“The idea was to give women options,” Hernandez says. “Women don’t like having to cut out carbs, especially when they are pregnant. A lot of times when they feel nauseated, carbs can help provide some relief.”

Researchers studied 46 women who were 28-30 weeks pregnant between 2015-2020. They were randomly put into two groups: the CHOICE diet, which consisted of higher complex carbs and lower fat, and the conventional diet, which had lower carbs with higher fat. Simple sugars were controlled and identical. All meals (except snacks) were provided for the entire study, and women recorded their meals and monitored their blood sugar levels four times per day. Women were also advised to exercise 30 minutes per day.

About two weeks after the baby was born, the mother and infant had their body composition (fat mass) measured at Children’s Hospital Colorado.

What they discovered was game-changing: both diets resulted in excellent blood sugar control. There also was no difference in newborn body fat or birth weight, maternal 24-hour glycemia, or insulin resistance. The diets were identical in calories and there was no difference in weight gain between the diets which was limited to ~ 4 lbs. from the start of the diet until delivery.

“We were surprised, but we were kind of hoping for those results,” Hernandez says. “What this means is that it establishes that one diet isn’t better than the other. Our research suggests women with diet-controlled gestational diabetes might have more options than we thought.”

Concerns About a Woman’s Diet

Hernandez wanted to conduct this study because she was concerned about diet patterns for pregnant women who eat a low-carb diet. During a low-carb diet, people tend to eat more fat.

“Women concerned about having a big baby would say, ‘I’m not going to eat carbs’. They cut carbs down to these low levels,” Hernandez says. “For example, women told me they would go to McDonald’s, order a McMuffin, and not eat the muffin. They were just eating the fatty part. That was their eating pattern, so I was concerned that women with GDM were eating too much fat.”

Hernandez says the principles shown in this study apply to the duration of a pregnancy, focusing on overall diet patterns and making healthy choices. Women should also control gestational weight gain since it is a main risk factor for gestational diabetes.

“Women with GDM are at a high risk for type 2 diabetes,” she says. “As a nurse, I took care of many, many men and women who had cardiovascular disease. A high percentage of them also had diabetes. So diabetes and cardiovascular disease co-exist.”

What Happens Next?

It’s unlikely a study like this will ever be conducted again. The study was technically difficult to achieve, mostly because all the food was provided to the participants. Hernandez says the hope is to take these findings and put them into international clinical guidelines.

“This isn’t about one diet over the other,” she says. “It’s about diet patterns. It’s important to have the right number of calories and to control simple sugars and saturated fat. We’re not saying to eat as many carbs as you want. You have to choose the right ones in the context of your diet pattern.”

“What we’re hoping will happen is that it will help providers, nutritionists, and certified diabetes educators with a broader range of options for women,” she adds. “This study will also lead to more research and more change.”

“The significant clinical impact of this study lies in its unique randomized controlled design in which all meals were provided, and calories were held constant for the remainder of pregnancy so that a rigorous comparison could be made between diets that varied only in macronutrient content, not calories,” Barbour says. “Demonstrating that up to a 100-gram difference in complex carbohydrates achieved similar glucose control and infant outcomes if simple carbs are avoided, fat is limited, and calories are controlled offers for the first time a choice to mothers with diet-controlled GDM that they can liberalize healthy carbohydrates with strong science behind it.”