"To some extent it's a matter of personality," Gerth said. "One child likes to eat, and eat a lot, and will eat anything. Another is fussy and eats like a bird."
Besides personality, psychological factors play a role. "Sometimes it's a display of independence," Gerth pointed out. Eating is a personal matter, he said, and by refusing to do so children are drawing a line between themselves and their parents with the message, "You're not going to tell me what to do". Trying to make them eat something against their will is especially ineffectual in their defiance phase and can even strengthen their defiant attitude, he warned.
"In many cases, children carp about food to be the centre of attention," noted Thomas Ellrott, director of the Institute for Nutrition and Psychology in the German city of Goettingen. Parents only make things worse if they argue with the child about food day-in and day-out, he said. Then the carping becomes a ritual.
"Parents' own eating habits also play a role, of course. Parents are, after all, role models for their children," said Ute Alexy, a member of the scientific staff of the Dortmund-based Research Institute of Child Nutrition.
Parents who regularly snack on chocolate and crisps, not fruit and vegetables, should not be surprised if their child does the same. By the same token, they can be a positive influence by setting a good example, "for example by eating a desirable food in front of the child with pleasure", Alexy said.
The way a child becomes acquainted with a food is also important. "Children are often sceptical towards unfamiliar things - a perfectly normal reaction that's a product of evolution," Alexy explained. If the first attempt at getting a child to eat a particular food is unsuccessful, parents should not give up, she said, but rather try and try again. "Unfortunately, it takes some children longer to accept unfamiliar foods."
Some children participating in food tests do not accept a food until the 18th time it has been presented to them, in fact.
The adaptation process can be accelerated by varying the way a food is prepared. A child who rejects carrot salad can be given carrot puree, for example. Or a food can be imaginatively dressed. Children are often more likely to try fruit and vegetables when they are shaped like animals or smiley faces.
If this fails to win a child over, there are other tricks to be tried, such as combining the disliked food with a liked one - vegetables with a blob of ketchup, for example - cooking together or regularly inviting the child's omnivorous best friend over for dinner.
Exhorting a child to eat by saying things like, "Come on. Eat it already. It's healthy", is counterproductive, according to Ellrott. "It'll make children associate 'healthy' with 'doesn't taste good'," he said.
Whatever the reason may be for a child's stubborn refusal to eat many foods, exasperated parents should never try to force the child to eat something.
"It's important that they always foster enjoyment at meals and not apply pressure," Alexy said. So while it is the responsibility of parents to offer their child balanced meals, the child should be allowed to decide what and how much to eat. Otherwise an eating disorder could result.
- AAP