Recent findings from the Diabetes UK-funded DiGest trial reveal promising results for mothers with gestational diabetes. We asked Diabetes UK to share with us the latest findings, which show that a modest reduction in calorie intake during the third trimester of pregnancy is not only safe but can also have significant health benefits for both mothers and their babies. With gestational diabetes affecting thousands of women each year, these findings could help reshape dietary guidelines and offer new ways to manage the condition.
By Faye Riley, Research Communications Manager at Diabetes UK
Findings from the Diabetes UK-funded DiGest (Dietary Intervention in Gestational Diabetes) trial, published in Nature Medicine, show that reducing calorie intake in pregnancy is both safe and beneficial for women living with gestational diabetes and overweight or obesity.
The DiGest trial explored if a reduced-calorie diet could safely help women with gestational diabetes and a BMI over 25 kg/m2 minimise weight gain during late pregnancy and improve health outcomes for them and their babies.
Professor Claire Meek, who led DiGest at the Universities of Leicester and Cambridge, explained, “We know that reduced-calorie diets promote weight loss and improve blood glucose levels for people with type 2 diabetes, but this has never before been tested in women with gestational diabetes.”
The trial was a randomised controlled double-blind study involving 425 women. Participants were randomly assigned one of two different diet boxes from 29 weeks of pregnancy until they gave birth. The boxes contained all their breakfasts, lunches, dinners, and snacks. One group received a standard healthy balanced diet of 2,000 kcal per day. The other group received a lower-calorie, nutritionally complete diet, of 1,200 kcal per day.
The researchers monitored several antenatal and postnatal outcomes for mothers and babies, including bodyweight, insulin requirements, and blood glucose levels.
What did DiGest find?
The study found that a reduced-calorie diet during the third trimester of pregnancy is safe for women with gestational diabetes and overweight or obesity, and their babies.
The reduced-calorie diet reduced the need for long-acting insulin therapy at 36 weeks. In the control group, 39% required insulin, compared to 28% in the intervention group. While more research is needed to explore the drivers of this effect, Professor Meek highlighted its potential impact. “If we used a lower calorie diet in pregnancy nationally, one in eight women with gestational diabetes could avoid needing long-acting insulin, which we estimate would benefit 8,000-9,000 women every year.”
Overall, 40% of participants lost weight (average of 3kg) during the third trimester. However, researchers did not find a significant difference in weight loss between the control and intervention groups.
Regardless, modest weight loss across both groups was associated with several health benefits. Women who lost weight had better blood glucose control, with more time spent in target range (80% vs. 71%) and lower average glucose levels (5.63 mmol/l vs. 5.94 mmol/l). They also had lower blood pressure and a 48% reduced risk of delivering a large for gestational age baby, compared to those who did not lose weight. This is associated with safer births, and as babies born larger than average have an increased risk of developing obesity and type 2 diabetes in later life, there could be potential life-long benefits for the next generation.
The research team also monitored women for three months after they’d given birth. Dr Laura Kusinski, Senior postdoctoral scientist at the University of Leicester, said, “Since women with gestational diabetes are at higher risk of going on to develop type 2 diabetes, we were very interested to see if modest weight loss in pregnancy would be helpful longer-term.”
The study found that women who’d lost weight in late pregnancy maintained their weight loss and improved blood glucose levels postnatally. These lasting benefits are important. “Women who lost weight in pregnancy saw longer-term benefits, with a lower weight and lower blood glucose levels at three months after the birth. This suggests that weight loss in pregnancy may be an effective and achievable way to reduce the risk of type 2 diabetes after gestational diabetes”, explained Dr Kusinski.
What’s the impact of DiGest?
It is normal and healthy to gain weight during pregnancy to support the baby’s growth and development, and current guidelines do not recommend weight loss during pregnancy for women with gestational diabetes. Instead, they focus on eating well to avoid gaining too much weight and to help manage blood glucose levels.
However, findings from the DiGest trial suggest that losing a small amount of weight – about 3kg – in the third trimester of pregnancy can safely minimise overall weight gain and offer health benefits for mother and baby.
The results could help inform new evidence-based guidelines on dietary advise and weight loss for women with gestational diabetes and overweight or obesity. They may also provide a new strategy to help prevent type 2 diabetes in this high-risk group.
Dr Elizabeth Robertson, Director of Research and Clinical at Diabetes UK, commented, “Gestational diabetes touches the lives of thousands of women in the UK each year. If left untreated, it increases the risk of poor health for them and their baby not only during pregnancy but over their lifetimes too.”
“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.”
Clodie RoIph, a participant in DiGest shared her experience, “I felt honoured and fortunate to be offered the opportunity to participate in the DiGest study. It was easy to do, I really enjoyed the food, and it helped manage my weight over the last trimester of pregnancy and have a healthy baby girl. Diabetes research like this is invaluable.”
Professor Meek added, “We are so grateful to the mothers who took part in the DiGest trial, and to the great team at the Universities of Leicester and Cambridge who supported our work. For women with gestational diabetes with a BMI over 25 kg/m2, following a lower-calorie diet in pregnancy is safe and healthy, both for mothers them and their for babies.”
Professor Meek hopes that most women with gestational diabetes and overweight or obesity could safely follow this kind of diet with guidance from their pregnancy diabetes care team, without needing extra medical supervision. A healthy version of a reduced-calorie diet should focus on low glycemic index foods, plenty of vegetables, lean proteins, and some dairy, to ensure enough nutrients. Cutting out entire food groups, like carbohydrates, is not recommended as low-carb diets may not be safe during pregnancy.
How long will it take until this diet becomes standard dietary advice for women with gestational diabetes and overweight or obesity?
In order to become standard dietary advice, a number of steps would need to happen including understanding the cost effectiveness, how to deliver this programme in an NHS setting and including in NICE guidelines on diabetes in pregnancy.
How would this dietary approach be delivered?
More research is needed to understand exactly how this dietary intervention could be delivered. The results of this study show that this approach is safe and beneficial, but the approach to supporting those with gestational diabetes and a BMI over 25 within routine clinical care needs to be explored further. It is likely that such an approach would be alongside the support of your healthcare team.
How does this approach compare to the standard dietary advice for gestational diabetes? Does this mean NHS guidance should be updated?
Current guidelines don’t recommend weight loss during pregnancy for women with gestational diabetes. Instead, they focus on eating well to avoid gaining too much weight and to help manage blood sugar levels. However, current international guidelines for weight change in pregnancy were developed for women without underlying health conditions and have not been customised for women with diabetes or obesity who are at increased risk of pregnancy complications.
Findings from the DiGest trial, suggest that losing 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 mother and baby.
The National Institute for Health and Care Excellence (NICE) has recently published updated guidance on weight management in pregnancy and highlighted dietary recommendations for gestational diabetes as a key area needing further research. DiGest begins to fill this gap. NICE guidance: Maternal and child nutrition: nutrition and weight management in pregnancy, and nutrition in children up to 5 years’
What’s next?
Professor Meek is now leading a three-year postnatal follow-up study to explore the long-term effects of modest weight loss in pregnancy, including its impact on type 2 diabetes and prediabetes rates in mothers and growth outcomes in their children.
Future research could also examine how modest weight loss during pregnancy could provide further benefits for long-term postnatal health, especially if combined with self-management and educational programmes.
