Reduced calorie diet in late pregnancy could aid women with gestational diabetes, Cambridge research suggests

A reduced calorie diet in late pregnancy is safe and beneficial for pregnant women with gestational diabetes, a study has shown.

The approach could benefit 13,000 women every year if rolled out nationally, researchers at the University of Cambridge and University of Leicester say.

One in 20 pregnant women develop gestational diabetes and most are advised to change their diet to manage blood sugar levels and reduce complications during pregnancy, birth and after birth.

But it has not been clear whether reducing calorie intake would be safe or helpful.

Prof Claire Meek, who led the Dietary Intervention in Gestational Diabetes (DiGest) trial in Cambridge and Leicester, said: “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.”

The trial involved 425 pregnant women with gestational diabetes and a body mass index (BMI) over 25 kg/m2, who tested one of two diets from 29 weeks of pregnancy until they gave birth - a standard healthy, balanced diet of 2,000 kcal per day and a nutritionally complete reduced calorie diet, which was nutritionally complete, of 1,200 kcal per day.

The participants completed weekly diet boxes with all their meals and snacks and the researchers monitored their weight, blood sugar levels, insulin needs plus their health and their babies’.

A reduced calorie diet during the third trimester of pregnancy was found to pose no health risks and was safe for women with gestational diabetes and their babies.

Just 28 per cent of women in the group on this diet needed long-acting insulin to manage their blood sugar levels, compared to 39 per cent of those on a standard diet.

This suggests it improved women’s insulin production or sensitivity, helping them to manage blood sugar levels more effectively.

“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,” said Prof Meek.

Across both calorie diet groups, women lost an average of 3kg in their third trimester and the researchers found no difference in weight loss between the groups.

However, there were several benefits for those had lost weight in either group including:

- Lower blood sugar levels and seven per cent more time spent in range and
- Improved blood pressure levels.

A 48 per cent 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.

Women were monitored for three months after they had given birth and the researchers found those who had lost weight in late pregnancy maintained their weight loss and improved blood sugar levels postnatally.

Such longer-term benefits are important because women with gestational diabetes have a tenfold higher risk of going on to develop type 2 diabetes.

Maintaining a healthier weight and more stable blood sugar levels can lower this risk.

The findings suggest modest weight loss - of around 3kg - in late pregnancy could be an effective way to reduce the likelihood of type 2 after gestational diabetes.

However, researchers stress that not all pregnant women with gestational diabetes need to lose weight. The findings apply to women with gestational diabetes who are overweight or living with obesity.

And there is no evidence that reducing calories or losing weight is safe or appropriate for other pregnant women.

Diabetes UK, which funded the study, stresses that the research took place in the third trimester of pregnancy, when the baby’s essential organ development has already taken place. There is no evidence reducing calories earlier on in pregnancy is safe.

Participants were closely monitored by healthcare professionals and pregnant women with gestational diabetes should not reduce their daily calorie intake to 1,200 on their own.

A three-year follow-up study is now under way to investigate any longer-term benefits, including the impact on type 2 risk.

Clodie Rolph, 42, from Suffolk, who took part in DiGEST, 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, which funded the work, 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.”