Does junk food during pregnancy give children a sweet tooth?

Eating junk food while pregnant increases the chance that your child is more likely to eat an unhealthy diet, high in sugar and fat, and be at increased risk of obesity, The Sun reported. “Mums who scoff doughnuts, biscuits, crisps and sweets pass on a taste for fatty and sugary snacks to their babies … kids are then more likely to opt for fast food in later life.”

The Independent reported: “Developing infants can have their eating habits programmed by their mothers’ food choices.” It quoted the researchers, who said it “could send offspring on the road to obesity and make the task of teaching healthy eating habits in children even more challenging.”

This stresses the need for a healthy diet during pregnancy. The newspapers also say that eating junk food while breastfeeding has a similar effect.

The original research is a study that investigated the effects of unhealthy junk food diet on pregnant rats’ offspring. Although the study suggests that this area could be studied further in humans, no conclusions can be drawn from this animal study about the effects on human babies of the mother’s diet during pregnancy.

Where did the story come from? 

Stephanie Bayol, Samantha Farrington and Neil Stickland of The Royal Veterinary College, London, UK, conducted this research. It was funded by the Wellcome Trust and published in the British Journal of Nutrition .

What kind of scientific study was this?

This was an experimental study in rats that was designed to try to examine the effects of diet during pregnancy and breastfeeding on the offspring’s diet, to see whether it could be a potential factor in the development of obesity.

In this study, rats were mated and, once they were pregnant, they were divided into two groups: 14 were fed on healthy, nutritional food and 28 were fed a junk-food diet with open access to biscuits, muffins and doughnuts, in addition to access to the balanced food.

After the birth, the first group of 14 rats continued on the same diet while suckling their offspring. Half the junk-fed rats continued eating junk food, and the other half switched to the healthy, nutritous food while the newborn rats were suckling.

After the newborn rats were weaned (at 21 days), the offspring of each of these three groups was divided into two. Half the litter was given junk food and the other half nutritous food, to give a total of six groups of offspring.

The offspring were then monitored until they were 10 weeks of age. Food intake and body mass index (BMI, calculated from body length and weight) of each rat was recorded daily.  Light beams were used to measure the level of activity of each of the rat groups. This allowed the researchers to monitor any effect that activity may have on BMI.

What were the results of the study?

The researchers found that the pregnant rats that were given open access to junk food chose to eat the junk and not the healthy food. They over-ate, and developed a greater BMI and reduced activity levels than the junk-food-fed rats. The results that were relevant for the offspring were:

• The junk-fed pregnant rats had lower birth weight offspring; this lower BMI was maintained in the offspring from mothers switched to healthy food from junk food while suckling.
• The three groups of offspring who were weaned on to junk food all over-ate, regardless of what the mother had eaten during pregnancy and suckling. The researchers found that the group of offspring who were in the junk-food eating group and were from a parent given junk both while pregnant and suckling ate the most of all three groups. These rats also showed a preference for eating food rich in fat and sugar over the protein-rich foods.
• The offspring who were weaned on to a healthy diet alone were not subsequently found to over-eat, even when the mothers had been fed junk food throughout pregnancy and suckling.
• There was no difference in activity levels between any of the groups of offspring.

What interpretations did the researchers draw from these results?

The researchers concluded that rats who are given open access to palatable high-sugar, high-fat foods will overeat and show a preference for these types of food. They found that if rats have been exposed to these foods while their mother was pregnant and suckling this makes the preference stronger, and that this could be prevented by eating a balanced diet while suckling. The study, researchers say, “emphasises that healthy eating habits should be encouraged, not only in young children but also in pregnant and breastfeeding women, to help combat the obesity epidemic.”

What does the NHS Knowledge Service make of this study?

This study is an interesting animal experiment into the effects of diet in pregnant and suckling rats. As the authors themselves raise, diet during suckling may play a key role in long-term appetite of offspring; it was the junk-food-eating offspring whose mothers were fed junk food during pregnancy and suckling that differed most from other groups. However, this research does not examine the effects of exposure to junk-food only during suckling.

It seems common sense that a healthy diet during pregnancy and breastfeeding would be the most sensible choice both for mother and baby. However, this study alone does not provide the evidence to support this conclusion in humans. The causes of the growing obesity epidemic among young people are complex and include many social, lifestyle and medical factors, of which diet during pregnancy and breastfeeding may or may not be one. Further studies of diet during pregnancy in humans are needed before even indications of a possible link can be made.