New research we funded has shown that a reduced calorie diet in late pregnancy is safe and beneficial for women with gestational diabetes who are living with overweight or obesity.
The findings lay the foundation for new clinical support that could help thousands of women with gestational diabetes avoid the challenges of insulin treatment and improve health for them and their babies.
The Dietary Intervention in Gestational Diabetes (DiGest) trial was led by Professor Claire Meek at the Universities of Leicester and Cambridge. The results, published today in Nature Medicine, will be presented at our Professional Conference in Glasgow next week.
Gestational diabetes can develop during pregnancy and affects around 1 in 20 pregnant women.
Most women with the condition are advised to make changes to their diet to help manage their blood sugar levels and reduce the risk of complications during pregnancy, birth and beyond. But it hasn’t been clear if reducing calories would be safe or helpful. This is what DiGest investigated.
Professor Meek explained:
“We know that reduced calorie diets promote weight loss and improve sugar levels for people with type 2 diabetes, but this has never before been tested as a way to help women with gestational diabetes minimise weight gain.”
What did the trial involve?
In DiGest, 425 pregnant women with gestational diabetes and a Body Mass Index (BMI) over 25 kg/m2 tested one of two different diets from 29 weeks of pregnancy until they gave birth:
- A standard healthy, balanced diet of 2,000 kcal per day.
- A nutritionally complete reduced calorie diet of 1,200 kcal per day.
Participants received weekly diet boxes with all their meals and snacks. The researchers monitored their weight, blood sugar levels, insulin needs and the health of mum and baby.
The results
The results confirmed that a reduced calorie diet during the third trimester of pregnancy did not pose any health risks and was safe for women with gestational diabetes and their babies.
Women following this diet were less likely to need long-acting insulin to manage their blood sugar levels.
In the standard diet group 39% of women required insulin treatment during their pregnancy, compared to 28% in the reduced calorie group. This suggests that the reduced calorie diet may have improved women’s insulin production or sensitivity, helping them to manage their blood sugar levels more effectively.
Professor Meek said:
“If we used a reduced calorie diet for this group nationally, we predict one in eight women with gestational diabetes could reduce their need for insulin, which we estimate could benefit up to 13,000 women every year.”
Across both the standard and reduced calorie diet groups, women lost an average of 3kg in their third trimester. Researchers didn’t see a difference in weight loss between the groups. But those who’d lost weight in either group saw several benefits compared to women who hadn’t. This included:
- Lower blood sugar levels and 7% more time spent in range.
- Improved blood pressure levels.
- A 48% lower risk of delivering a large baby. This is linked to safer births and reduced risks of obesity and type 2 diabetes for the child later in life.
The research team continued to monitor women for three months after they’d given birth. They found women who lost weight in late pregnancy maintained their weight loss and improved blood sugar levels postnatally.
These longer-term benefits are important because women with gestational diabetes have a tenfold higher risk of going on to develop type 2 diabetes.
Since maintaining a healthier weight and more stable blood sugar levels can lower this risk, these findings suggest that modest weight loss in late pregnancy could be an effective way to reduce the likelihood of type 2 after gestational diabetes.
Professor Meek and team are now running a three-year follow-up study to further investigate any longer-term benefits, including the impact on type 2 risk.
Clodie Rolph, 42, from Suffolk took part in DiGEST. She said:
“I was really surprised, and a little upset, when I found out I had gestational diabetes. Taking part in the DiGest study has had a really positive impact on my health and I’m so grateful to have been given the opportunity.
"It was easy to do, I really enjoyed the food and it helped manage my weight over the last trimester of pregnancy. Although challenging at times, all the extra monitoring, eating healthier and being more active was worth it to have a happy, healthy baby girl.”
Dr Elizabeth Robertson, Director of Research and Clinical at Diabetes UK, said:
“We’re proud to have funded this pivotal research that addresses a critical missing piece in our understanding of how to safely treat gestational diabetes with dietary changes. With this new understanding, we have the opportunity to help more mothers experience a healthy pregnancy, give birth to healthy babies, and reduce their risk of type 2 diabetes in the future.”
What does this mean for people with gestational diabetes?
It’s normal and healthy to gain weight during pregnancy to support the baby’s growth and development. But gaining too much weight can carry risks.
These findings suggest that clinical support to lose a small amount of weight (around 3kg) in the third trimester of pregnancy is a safe way to minimise overall weight gain, and is linked to health benefits for mum and baby. But this approach might not be suitable for everyone.
It's important to note:
- Not all pregnant women with gestational diabetes need to lose weight. And these findings apply only to women with gestational diabetes who are living with overweight or obesity. There’s no evidence that reducing calories or losing weight is safe or appropriate for other pregnant women.
- This study took place in the third trimester of pregnancy, when the baby’s essential organ development has already taken place. There’s no evidence that reducing calories earlier on in pregnancy is safe.
- Participants were supported by healthcare professionals who made sure they were monitored closely, and their diet was nutritionally complete.
If you’re living with gestational diabetes and overweight or obesity and considering making changes to your diet, it’s essential to first talk to your healthcare team for personalised support on how to do so safely. Pregnant women should not reduce their daily calorie intake to 1,200 on their own.
