Mum's fatty diet and obesity

Mothers who eat an unhealthy diet in pregnancy may cause their children to over-eat in later life, the BBC's news website reports.

But the study the story is based on was carried out on rats, and its relevance to humans is not clear.

“A high-fat diet in pregnancy may cause changes in the foetal brain that lead to over-eating and obesity early in life,” the website reports. It is based on an animal study that found that when pregnant rats were fed a high-fat diet, their babies, “Ate more, weighed more... and began puberty earlier”.

It’s important to maintain a healthy balanced diet throughout life, including during pregnancy. Pregnant women should follow advice from their doctors and midwives about their diet, as sometimes they may need to eat more or less of certain foods to support the healthy development of their baby.

Where did the story come from?

Dr Guo-Qing Chang and colleagues from The Rockefeller University in New York carried out this research. The study was funded by the National Institutes of Health in the US. It was published in the peer-reviewed Journal of Neuroscience .

What kind of scientific study was this?

This was an animal study that looked at how a high-fat diet in pregnant rats affected the brains of their offspring. In particular, the researchers were looking at whether the levels of proteins which stimulate the appetite (called orexigenic peptides) were increased in the brains of the offspring because the mothers had eaten a high-fat diet.

The researchers fed half the group of pregnant rats with a high-fat diet (50% fat) and fed the other half with a balanced diet (25% fat) from the sixth day of pregnancy until giving birth (about two weeks). The rats could eat as much of the food as they wanted, whenever they wanted. Three times a week, the researchers measured how much the rats ate, and they were weighed weekly. Overall, throughout their pregnancies, the high-fat and balanced diet rats ate a similar amount of calories and they had similar weights at the time they gave birth.

After the rats gave birth, the babies of the high-fat diet mothers were divided into two, and half were given to the balanced-diet mothers to foster. The other half remained with their mothers, who continued to be fed a high-fat diet until 15 days after the birth. Offspring from high-fat and balanced-diet mothers were followed from the time they were weaned (21 days after birth) until a few weeks after puberty (70 days after birth). Only male offspring were followed up after birth.

During follow-up, the rats’ behaviour and physiology were assessed, and their weight and body composition were measured. All the groups of offspring were given access to a balanced diet until day 50, and after this they were given access to both the balanced diet and the high fat diet for 10 days. The researchers looked at the levels of the appetite-stimulating proteins in the rats’ brains during their development. They compared the brains of all the differently fed groups of offspring and investigated how any changes might be occurring.

What were the results of the study?

The researchers found that the offspring of mothers that were fed a high-fat diet during pregnancy had higher levels of appetite-stimulating proteins in their brains. This increase started when the offspring were in the womb (from day six of gestation) and lasted up to 15 days after birth. The high-fat diet seemed to stimulate the nerve cells in certain regions of the brain to divide more often, and to develop into cells that produced appetite-stimulating proteins.

The babies of the mothers fed a high-fat diet during and after pregnancy had higher body weights at 30 and 70 days after birth than the babies whose mothers were fed a balanced diet. The offspring of the mothers fed a high-fat diet during and after pregnancy also had higher calorie intake, preferred the high-fat diet to the balanced diet and had higher levels of fats in their blood. By day 70 there were similar changes in the offspring of the mothers fed a high-fat diet during pregnancy which had been fostered to balanced-diet mothers.

What interpretations did the researchers draw from these results?

The researchers conclude that the brain changes they saw in the offspring of mothers fed on a high-fat diet, “May have a role in producing the long-term behavioural and physiological changes observed in offspring after weaning”. They suggest that this effect might have contributed to “the increased prevalence of childhood obesity over the past 30 years”.

What does the NHS Knowledge Service make of this study?

This study expands on previous work that has shown that in animals such as rats, maternal diet during pregnancy can affect the offspring’s feeding behaviour. Although this work has identified some changes in the brains of the rats that might contribute to this phenomenon, it is not possible to say whether these findings apply to humans.

It is important to maintain a healthy balanced diet both during pregnancy and after the baby is born. Pregnant women will have different dietary requirements to women who are not pregnant, and they may need to eat more or less of certain foods to support the healthy development of their baby. Pregnant women should follow advice from their doctors and midwives about their diet.

NHS Attribution