Mothers-to-be child obesity warning

The same applies to mothers who are breastfeeding, scientists have warned.

Unborn babies and developing infants can have their eating habits programmed by their mothers' food choices, according to the findings.

Children exposed to "maternal junk food" in the womb or early in life may find it harder to resist an unhealthy diet as they grow older, say the researchers.

Dr Stephanie Bayol, from the Royal Veterinary College in London, said: "Our study has shown that eating large quantities of junk food when pregnant and breastfeeding could impair the normal control of appetite and promote an exacerbated taste for junk food in offspring.

"This could send offspring on the road to obesity and make the task of teaching healthy eating habits in children even more challenging."

Controlling appetite involves hormones which act on the brain to regulate energy balance, hunger and satiety - the sensation of "feeling full".

However feeding is not merely mechanical. It is partly governed by "reward centres" in the brain whose pleasure responses may override normal "feeling full" signals.

Previous research has shown that junk foods rich in fat and sugar inhibit satiety while promoting hunger and stimulating the reward centres.

The new research, carried out on rats, indicates that even before birth, exposure to junk food may induce an unhealthy taste for fatty, sugary treats.