Everyone knows a picky eater. There's always that one friend who won't eat foods that touch each other or vegetables of a certain color. Perhaps even you were a picky eater as a child, preferring to have only one particular food on your plate.

Most of us outgrow these food habits. Or at the very least, we learn to introduce other foods for a somewhat balanced diet. But sometimes, a person emerges who is determined to put all other picky eaters to shame.

Dan Janssen is this person. And whether you're grossed out by his habits or an admirer of his courage, there's undoubtedly something very special about him.

NOTHING BUT PIZZA.

For over 25 years, Dan Janssen has eaten nothing but pizza. No pasta, no eggs, no salads, just pizza. It all started when he was a teenager. Dan, a wood craftsman based in Maryland, decided he was going to eat to cut meat out of his diet for ethical reasons. Ordinarily, this would still leave a person with many options.

But Dan also hated vegetables and so he started to eat pizza to supplement his bare-bones diet. He realized he didn't particularly miss other foods, so as he ascended into adulthood, Dan made pizza the main and single member of his dietary food group.

Since he doesn't eat meat and hates vegetables, the only pizzas he's eaten since then have been the cheese variety. That right. Nothing but dough, tomato sauce and cheese - with the occasional addition of mushrooms.

But Dan's diet has led to some pretty serious health problems.

He's been diagnosed with diabetes and he frequently has low blood sugar. When he has a diabetic episode, he's been known to pass out wherever he is. In fact, he once wrecked a brand new car when he passed out behind the wheel and swerved off the road.

But Dan's diet is also related to traumatic experiences he had as a child. As a five year old, he was kept in a closet by his babysitter when he refused to eat her Brunswick stew.

That same year he was rushed to the hospital after being fed some poisonous mushrooms. The memory of throwing up uncontrollably that night after drinking an antidote of Coca-Cola and Karo syrup was enough to put him off vegetables for the rest of his life.  

These days, Dan sees a therapist to help him understand his aversion to other foods. But he says the only reason why he sees her is because her office is near one of his favorite pizza spots.

To make up for his vitamin-deficient diet, his fiancee makes him drink a smoothie full of proteins and fibers. But Dan says he'll probably eat only pizzas till he dies.

He's not sick of it and does not think his health problems are serious enough to force him to include other foods into his diet. He encourages others to eat only the food that make them happy.

"There's a lot of guys, a lot of women out there too who say 'I'd love to do that everyday,'" Dan says. "You can."