I saw one of the white-food kids a couple of weeks ago — a 9-year-old boy who lives on French fries, chicken fingers, white rice and white bread. Some white-food kids are so strict that their parents have to warn the restaurant that if there’s a little ceremonial dusting of parsley on the French fries, the child won’t eat them.

My patient’s mother was despairing: He won’t touch a vegetable, she said. He isn’t getting any healthy food at all. Some picky eaters are scrawny, but this one was chunky. In fact, it’s surprising to me how often a parent tells me, if I express some concern about the rapid rate of weight gain, that the child hardly eats anything, the child has no appetite, the child is incredibly, heartbreakingly, picky. And though I could tell you a perfectly true story about a mother who said just that as her child sat in the exam room, munching his way through a large bag of pizza-flavored Doritos, the truth is that it can be genuinely painful for parents to watch their children refuse food, and worry that they are somehow failing to provide the necessary vitamins, protein and vegetables.

People are often pretty judgmental about picky eaters, disapproving strongly of the children themselves (“So unadventurous, so fearful of new tastes!”); of their parents (“Don’t they know it’s their responsibility to make the rules!”); and, inevitably, of our degenerate and too-permissive times (“Why, when I was a child, we ate what was put in front of us, and no nonsense!”).

Dr. Natalie Muth, a pediatrician in Vista, Calif., near San Diego, who is also a registered dietitian and the co-author with Sally Sampson of “The Picky Eater Project,” to be published by the American Academy of Pediatrics next month, told me that it’s important to expose children to different flavors even through what the mother eats during pregnancy and breast-feeding. (The techniques used in the book were explained in more detail last year in a series of posts on the Motherlode blog.)

She said many children become comparatively picky around the age of 2, so it’s important to expose younger children to many foods, many times. They are more open to trying new things in that first year of eating solid foods, between 6 and 18 months, and multiple exposures help them learn to like different flavors.

“I talk about training your taste buds; it can take a lot of tries to like something,” Dr. Muth said. “You don’t even have to chew and swallow, just take it on your tongue.”

And that 2-year-old who may be developmentally more neophobic — nervous about new things — also is developmentally ready for all the struggles of separation and independence. “We’re all born liking sweet and salty, and a 2-year-old is no exception,” said Dr. Muth. “But also, a 2-year-old is trying to assert himself.”

When those struggles persist around food, and parents find themselves faced with that picky eater, the idea is to go on offering foods, go on encouraging repeated tastes, go on letting the child see other family members eat different foods — to do all that but to let the child make the actual decisions about what to eat. “There’s a division of responsibility, which was first described by the dietitian Ellyn Satter,” Dr. Muth said, “parents choosing what’s offered and when, the child choosing what to eat of what’s offered.”

As a pediatrician, I worry when children don’t gain weight — or sometimes, when they gain too much, like some white-food eaters. We start with the assumption that picky eaters are just picky, and studies have shown that while they may not eat many vegetables, they generally take in about the same amount of food as other children.

Parents may find it helpful — and reassuring — to give multivitamins to children whose diets are very limited, even as they are encouraging them to expand their range.

“A hungry child will eventually eat,” Dr. Muth said. “Your best shot is having your child hungry at mealtimes when there is a variety of food.”

And though it can be a long process, Dr. Muth says, she encourages parents to keep trying, and not to give way to the temptation to create parallel meals. “One family, one meal,” she said. “Maybe include something that your child will eat, but don’t cater to the picky preference by making a second meal or making some alternative always available.”

The child will either come around or else learn to cook, she said, and children who do learn to cook have been shown to be more interested in trying new foods.

This can be a long process, and very distressing for parents; pediatricians can help make sure that the child is, in fact, growing normally, and help address the question of whether something else might be going on.

In those rare cases when a child doesn’t grow properly, you have to consider more serious issues, from food allergies and GI problems to autism and other developmental issues.

I have a pediatrician friend whose own baby wouldn’t eat. He did fine on breast milk and formula, but when it came time to make the transition to solid foods, he just didn’t seem to have any appetite. It was impossible to get food into him, and his growth failure was significant enough that his pediatrician began diagnostic tests for some of the many possible syndromes and chronic illnesses that can cause what we call failure to thrive.

The child was also slow to start talking, and it was his speech therapist who suggested that there might be a connection to his difficulties with eating. He needed specialized occupational therapy to help his mouth do its various jobs; when he got better at chewing and swallowing, he began to gain weight and grow.

But most children don’t have a serious medical problem. Yet despite a parent’s best efforts to offer a variety of foods, some children are pretty resistant. I know that the mother of that 9-year-old in my exam room thought that she was failing her son, and she probably worried that I was judging her for his weight gain, and for giving him all that white food, which was the only food he would eat.

Those were not the messages I intended to send, but the emotional overtones of eating and feeding continue to be powerful for parents, as their children grow up. We feel directly responsible for what our children eat — and what they don’t eat — but the negotiations around autonomy and responsibility are more complicated than that.

“It’s not a lost cause,” Dr. Muth said. “We can help kids be more healthy and adventurous eaters, but it takes time.”