Vlad Averbukh says he'll need a napkin at lunch. "It could be bloody." What he doesn't require is a fork. A follower of America's "paleo diet," or simply "the caveman lifestyle," New Yorker Averbukh does things the old-fashioned way.
"A lot of folks might find this unpalatable. But to me it tastes good," he says, lifting an uncooked cut of beef the size of a book.
Chomping on the raw meat in a small park by the Hudson River, Averbukh, a 29-year-old website manager, explains how paleo dieters are trying to turn mankind's clock back to the Paleolithic Era.
"The theory is that you only eat what our ancestors ate 10,000 years ago. It's what you could get with a stick in the forest," Averbukh says.
Professor Loren Cordain, author of "The Paleo Diet," bemoans the world's dependence on cereal grains, saying the departure from prehistoric menus has led to "diseases of civilization" like cancer, obesity and high cholesterol.
The Stone Age diet prioritizes seasonal fruit, lean meat, fish and very little intake of processed food, sugar, grains - including bread - or dairy products.
Many modern cavemen also like to fast and to eat at irregular times, much like those early hunter-gatherers.
The program is "not designed by diet doctors, faddists, or nutritionists, but rather by Mother Nature's wisdom acting through evolution and natural selection," Cordain writes on his website.
Along with pure, mostly raw food, the modern caveman adapts his exercise to mimic the exertions of hunting - or being hunted - instead of today's emphasis on endurance running or building muscles in the gym.
A guru from the paleo world's European wing, Frenchman Erwan Le Corre, conducts training sessions in the wild, throwing rocks, jumping, and running barefoot.
Men's Health magazine calls Le Corre "a perfect twin for Tarzan" and possibly "one of the most all-around physically fit men on the planet."
Averbukh, who builds websites, looks about as unlike a savage as you can get. Slight, with trimmed hair and beard, he is indistinguishable in his grey pleated trousers and black shoes from the crowds of office workers filing through lower Manhattan on a weekday.
The first clue that something might be different is when Averbukh starts doing pull-ups from a section of scaffolding. Deceptively strong for his frame, Averbukh pulls himself up with ease, then goes to a wall to stand on his hands.
"I like to do my exercise before I eat," he says. "The diet and exercises go together. It was part of our ancestors' lives. They had to exercise because they were hunting for food. We still need it."
Devotees swear they are healthier and more at peace than the millions of stressed, poorly nourished, overweight people outside the cave, or what Le Corre calls "zoo humans."
There are difficulties. Averbukh admits some friends find him a "freak" and he tries to make sure no one's around when he does his impromptu exercises.
For example, his habit of sprinting down streets in office clothes can attract unwelcome attention. "Once the cops really thought I'd stolen something," he said.
Neither is the ultra-simple life cheap. Paleo diners will only buy grass-fed organic meat and organic fruits and nuts. Averbukh reckons on a winter food budget of about 70 dollars a day.
The lifestyle also faces an uphill battle in attracting cavewomen. A city like New York teems with health-conscious females, but they typically favor lettuce and yoga over animal fat and street fighter-style acrobatics.
"It may not be as sexy and feminine to eat raw meat and animal products," Averbukh concedes.
One strong female backer of the paleo diet is Allison Bojarski, at the training program CrossFit NYC. She calls for "eating a diet that is in line with how humans co-evolved with their plant and animal environment."
But Bojarski draws lines at the extras. "I'm not about some crazy re-enactment of caveman times and lifestyle."
Certainly mainstream dieticians are unlikely to sit down any time soon at the Stone Age table.
"What we know from science, not just cavemen, is that a diet full of fruits, vegetables, fruits and plenty of whole grains, lean protein and healthy fats - that's what leads to longevity," said Keri Gans, spokeswoman for the American Dietetic Association.
"Let's think about how the cavemen lived. They didn't have very long lives," she added. "Unfortunately it's another fad. It's another gimmick of a diet."
Nutritionist Marissa Lippert called the diet "interesting" and said there was nothing wrong with very high quality, grass-fed meat.
"But the diet falls short in a couple of ways. We've evolved as a civilization over thousands and thousands of years," she said. "You're forgetting all the great sources of grains and really healthy complex carbohydrates."
Undeterred, Averbukh says urban cavemen are not only healthier, but a lot of fun. Next week, he's going out with a group to a farm "to visit the grass-fed animals."
He scoffs at grain eaters, vegetarians and "misinformation" about red meat.
In fact, he's already looking forward to his next meal: "Fatty bone marrow and then some berries."