Mamas on Bedrest: The Skinny on Low Glycemic Index Diets and Gestational Diabetes

December 5th, 2011

Gestational Diabetes is on the rise and is increasingly the cause of excessive weight gain during pregnancy, difficult delivery and injury during delivery to both mother and baby. According to a MedScape Reference Article,

“Abnormal maternal glucose regulation occurs in 3-10% of pregnancies, and gestational diabetes mellitus (GDM), which is defined as glucose intolerance of variable degree with onset or first recognition during pregnancy, accounts for 90% of cases of diabetes mellitus (DM) in pregnancy. However, the rising prevalence of diabetes mellitus—21 million people (7% of the population) have some form of diagnosed diabetes; another 6 million people may be undiagnose —particularly type 2 among women of childbearing age in the United States, has resulted in increasing numbers of pregnant women with preexisting diabetes. Currently, type 2 diabetes mellitus accounts for 8% of cases of diabetes mellitus in pregnancy, and preexisting diabetes mellitus now affects 1% of all pregnancies.”

Scientists at the University of Sydney in Sydney Australia have done extensive research into glucose metabolism and have been at the forefront of the Low Glycemic Index research. Through their research, they discovered that not all foods and in particular not all carbohydrates, are metabolized equally. While some foods, proteins for example, are metabolized slowly requiring more time to be broken down resulting in a steady release of energy (sugar) into the blood stream, other foods are very rapidly broken down (simple sugars such as those in processed foods), causing spikes in blood sugar levels and stressing the body to rapidly remove the excess blood sugar from the blood stream. Much of their work is posted on a very useful website called The Glycemic Index.

Jennie Brand-Miller, PhD is one of the leading experts on the Glycemic Index. She and her colleagues at the University of Sydney conducted a study to determine if a low glycemic index (LGI) diet could have an impact on pregnant women’s glucose metabolism (reducing sugar spikes and insulin resistance) and hence lower their chances of developing gestational diabetes and the associated complications for mothers and babies.  They compared a LGI Diet with a High Fiber Diet in 99 pregnant women diagnosed with Gestational Diabetes between 20 and 32 weeks gestation. They assigned the women to one of two healthy diets containing similar proportions of protein, fat and carbohydrate — but one with a low glycemic index (target GI <50) and the other with a high-fiber (HF) content and moderate GI (target GI ~60).

The researchers found that fewer women gained excessive weight on the LGI diet (25%) than the HF diet (42%), and fewer needed insulin treatment (53% vs. 61%). However, newborn outcomes were virtually the same in both groups. Mean birth weight in both arms was 3.3 kg (7.26 lbs), the rate of macrosomia (excessive nutrient {fat} storage in the infant) was 2.1% with the LGI diet compared to 6.7% on the HF diet. While these differences were noted, they were not statistically significant, and hence the researchers concluded,

“this randomized controlled trial of an LGI diet versus a conventional high-fiber diet found no differences in key pregnancy outcomes in GDM.”

While its easy to appreciate the scientific method behind their conclusions, I respectfully disagree and hope that people (pregnant women at risk for or who may have developed gestational diabetes) won’t read this information and essentially “toss all caution to the wind”.

Often in science a finding is given value only if it shows a statistical significance.  This means that there has to be a specific, measurable numeric difference between that which is manipulated in the study and the control to make the results relevant. While that makes sense in many cases, (in a medication trial for example with no measurable benefits and potential negative effects should not be prescribed!), should all “scientific” findings be evaluated this way? This question becomes important in this case when we look at the findings of the study. Women who were put on the LGI diet were less likely to gain excessive weight and were less likely to require insulin. Yet, because the birth outcomes of the babies didn’t yield significant differences, they authors seem to say, “there is no value in following a LGI diet if you are pregnant and at risk of developing gestational diabetes.

That’s where things get sticky. It is well known that it isn’t safe for mothers to gain excessive weight during pregnancy as the excess weight can lead to complications such as Gestational Diabetes, dysfunctional labor and labor and delivery complications (especially in the case of cesarean sections). So if there is a method, essentially a lifestyle change, that can help mothers curb excessive weight gain which would lead to a reduction in these outcomes, which is non-toxic to mothers and their babies, even though there is no guarantee that babies won’t store excess fat, why not at least try it? Additionally, mothers who followed a LGI diet were less likely to require insulin. Isn’t that a good enough reason to recommend a LGI diet for women at risk?

Science is a good thing and it’s a good thing to make medical recommendations based on well designed, evidence-based research. However, we cannot become so rigid in our thinking and “throw the baby out with the bath water” when the science shows promise, but the numbers are not “statistically significant.” In my opinion, if a woman is at risk for developing gestational diabetes or has been diagnosed with gestational diabetes, I think that she should be educated about the glycemic index and counseled to make low glycemic food choices.

If you are a mama on bedrest and want to learn more about making the Glycemic Index and following a LGI diet, sign up for our Complimentary 30 min Bedrest Breakthrough Session. It’s a way to learn the basics Low Glycemic eating and foods and products we’ve found to be helpful in maintaining a low glycemic diet. To schedule your complimentary consultation, share a comment below or send an e-mail to

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