How many people can't stand the texture of fish, can only stomach grilled chicken or refuse to eat their vegetables?
Scientists at Duke University in North Carolina are compiling the first global registry of "picky eaters" in the hope of discovering why some people have trouble with food.
They believe it may help find a genetic reason for some eaters' intense dislike of certain foods, like broccoli, or beans with a "fuzzy" texture.
They note some eaters' pickiness is so deep-seated it interferes with their jobs, their relationships and their social lives.
"This is an area that is vastly under-explored," says Dr Nancy Zucker, director of the Duke University Center for Eating Disorders.
"We have no idea how prevalent it is and how it affects people's lives."
The findings have given heart to picky eaters who say they are not taken seriously because most omnivores consider their fussiness a choice or a childish habit, not a medical condition.
Neither is picky eating socially acceptable, in the way that vegetarianism or other voluntary diets are.
"The worst thing about being a picky eater is other people," says Rhonda West of Virginia.
"They're just mean. It starts with your family thinking you're doing this on purpose, that you're trying to gain attention or just being a difficult child - but it's none of the above. They're asking us to do something that's equivalent to eating dirt every day."
Rice swallowed whole
Ms West, 42, says she began rejecting food as an infant, refusing to breast feed or accept substitutes.
As an adult she only eats fruit, white rice swallowed whole because she doesn't like the texture, French fries, and plain meat.
"Texture is just as important to me as taste, because if something is slimy, like pasta or sea food it sends my senses to the moon," Ms West says.
"Tomatoes look good but I can't get past the squishiness. It's like biting into a big fat maggot."
Eating pasta is like "having a live worm in your mouth", she says.
Research into obesity, food cravings and how people perceive different tastes has raised the possibility that genetics are responsible for picky eaters' finicky tastes.
Professor Beverley Tepper, of Rutgers University in New Jersey, is part of a group researching why people react differently to chemical compounds in food.
She says the ability to detect bitterness is inherited and contributes to people's preferences for some foods rather than others.
"Taste differences are a combination of genetics and personal characteristics, but there are other variables - some of it might be psychological."
"Maybe there are genes out there that cause picky eating. We don't know yet."
Ms West is convinced she was born with her food preferences, although she says they were compounded by constant childhood battles with her parents, who tried to force her to eat foods she didn't like.
Jenny Nikolaisen of Virginia also believes genetics play a role because she comes from a long line of picky eaters. For the most part, she eats only plain meat and potatoes, baked or fried, and has the same meal of hamburger and chips for lunch virtually every day.
"A lot of times when I try something new, it causes me to gag," says Ms Nikolaisen, 34, adding that at times she can talk herself into eating foods not on her usual menu.
"I tried broccoli once and it felt like little trees in my mouth," she says.
"It was a really weird feeling and I never tried it again."
Like many picky eaters, Ms Nikolaisen feels excluded from social situations because people criticise the way she eats.
"When you say you don't want this or you don't want that," she says. "They think you're closed-minded and that you're like that in every area of life, and that's just not the case."
Influence on children
James Matta of Rhode Island lives off white carbohydrates - bread, pasta, pizza and potatoes.
He doesn't like chicken or green vegetables but will eat some fruit. He prefers processed, pre-packaged meals.
"It's hard to accept this about myself," says Mr Matta, 47.
"This issue has been a problem for me throughout my entire life. I think it's psychological, from being told to eat food I don't like and having the obsessive thought that I'm going to throw up. But I would like to know whether it is a medical condition."
Some picky eaters are so convinced that their behaviour is genetic that they're frightened of passing it to their children.
"My daughter and I are both picky eaters even though I have done everything in my power to make her unlike me," says Heather Hill of North Carolina.
"I wouldn't even eat in front of her because I didn't want to mess her up."
They eat macaroni and cheese, crackers, chocolate milk and French fries, but Ms Hill, 40, says they're fit and healthy.
"People think this is something you choose, but I don't have a choice," she says.
"Could I physically do it? Eat something I don't like? Probably. But I would vomit."
Thousands of picky eaters have already taken a Duke University survey, but Dr Zucker says it's too early pinpoint any single reason for their food preferences.
Even if the research doesn't find a medical reason why some people can't stand certain foods, picky eaters hope it will at least give them some scientific recognition and help lessen the social stigma.
"There are people with definite biological vulnerabilities, influenced by experiences that have shaped them," Dr Zucker says.
"I think we can pretty safely say it's going to be many things. We're also hoping to learn from the people who are struggling, what they have found that helps them.
"That will fuel intervention strategies for people who want to expand the range of foods they eat."