“Mums who eat cake can make their babies fat” is the headline in the Daily Express today. It says that mums “who eat cakes and takeaways while pregnant or breastfeeding could end up with fatter babies”.
The newspaper reports are based on a study carried out in pregnant rats and their offspring. The offspring of rats fed a diet rich in hydrogenated fats during pregnancy and lactation had an increased level of body fat. The effects in pregnant women may not be the same. Mums will already know that a healthy, balanced diet is important, both for their children and for themselves when they are pregnant and breastfeeding.
Where did the story come from?
Dr Luciana Pisani and colleagues from São Paulo Federal University in Brazil carried out this research. The study was funded by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). It was published in Lipids in Health and Disease , a peer-reviewed scientific journal.
What kind of scientific study was this?
This was an experimental study in rats to see whether feeding the mothers a diet high in hydrogenated fats while they were pregnant and lactating would have any effect on eating patterns, weight or body fat in their offspring.
The researchers took rats at the beginning of their pregnancies and randomly assigned them to either a normal diet (controls) or a diet enriched with hydrogenated vegetable fats, which are rich in trans fatty acids. This diet was maintained through the pregnancy and lactation. Once the rats’ offspring were weaned (when they were 21 days old), the researchers took the male offspring and either fed them the control or fat-enriched diet. The offspring were weighed and their food intake recorded every week.
After 90 days, the researchers looked at the offspring’s body fat content, as well as the expression of genes and the levels of various proteins in the offspring’s tissues. It was not clear exactly how many pregnant rats were used in total; at least 40 offspring were examined.
What were the results of the study?
The researchers found there was no significant difference between the weights of the offspring when weaned from the different maternal diet groups. However, by seven weeks, the offspring whose mothers were fed the fat-enriched diet ate less food and weighed less than rats whose mothers were fed normal diets.
Rats whose mothers were fed the fat-enriched diet, and who ate the same diet themselves, had reduced metabolic efficiency. This means that they had to eat less food to put on the same amount of weight than the other groups. Offspring who ate the fat-enriched diet had about 40% greater body fat content than the other groups, regardless of their mothers’ diets. These rats also had higher levels of insulin receptors than the other groups.
What interpretations did the researchers draw from these results?
The researchers concluded that consumption of hydrogenated vegetable fat during pregnancy and lactation could have negative effects on the offspring, even if the offspring themselves do not eat this diet.
What does the NHS Knowledge Service make of this study?
This study suggests that the diet of pregnant and lactating rats may affect their offspring’s food intake, weight and body fat content. However, this experimental situation is in no way comparable to a human diet. Pregnancy and lactation in rats are not the same as in pregnant women. Mums will already know that a healthy, balanced diet is important, both for their children and for themselves when they are pregnant and breastfeeding.
Sir Muir Gray adds...
The headline should have read ‘Mothers who consume more energy than they need may put on weight, and have fatter babies’; as Marie Antoinette might have said – let them not eat more cake!