A low glycaemic (GI) diet during has no significant impact on infant birth weight, but can substantially lessen maternal weight gain, an Irish study has found.

The study found that women who went on a low GI diet during pregnancy gained less weight than those who did not go on the diet.

Of the 800 women who took part in the study carried out by Prof Fionnuala McAuliffe and Dr Jennifer Walsh of UCD, the low GI group gained an average of 1.5 kilograms fewer in weight than the group that received no dietary intervention.

A low GI diet is a weight-loss diet based on controlling blood sugar, including controlling certain carbohydrates. Carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream, have a low GI.

The UCD research also found that a low GI diet during pregnancy led to better control of sugar levels, therefore translating into fewer cases of diabetes during pregnancy (gestational diabetes).

Prof McAuliffe said the findings had important implications for the maternal and subsequent health of women, particularly those who might be prone to excess weight gain during pregnancy and those at risk of poor control of sugars.

"The results of our study indicate that a low GI diet has a significant positive effect on gestational weight gain and maternal glucose intolerance, which means a healthier mother and a healthier infant."

Prof McAuliffe, of the National Maternity Hospital and the UCD School of Medicine and Medical Science, was awarded first prize for research for the study at the recent annual meeting of the Society for Maternal-Fetal Medicine in San Francisco.

The research was supported by grants from Health Research Board Ireland and the EU.