For decades men kept their mouths shut about what they ate unless they had a favorite burger haunt or a choice tip for grilling steaks. But things have changed. In Austin not long ago, during a picnic at his son's Montessori school, an advertising executive named Adam Butler was approached by Ezra Pagel, a 35-year-old software engineer. Pagel saw Butler carrying an Engine 2 bag. "Are you doing that diet?" he asked. Pagel himself was modifying his meals, holding fast to the guidelines of the Paleo "If you can't hunt or gather it, you can't eat it" Diet, which the 36-year-old Butler—a vegan—calls "intractable and Luddite." "It's such man-casting," he adds. "You're a freaking caveman, bro." Pagel is just as quick to speak up on behalf of his grocery list. He believes that humans are meant to eat meat. "Our teeth indicate that," he says. "Plus, it tastes damn good."

Despite their conflicting viewpoints, the two wisely avoided a full-blown food fight in front of their children. "It's kind of like talking about politics," Pagel says of the country's increasingly polarized diet debate. "I veer away from it." Easier said than done. The days when men fought over the last hot dog on the grill are long gone. Now they're more likely to throw down over wild boar vs. tempeh. They marvel that, thanks to their food choices, they no longer have to control portions, they feel healthier, and they have more energy. Some even rhapsodize about how their regimens make their bowels more efficient. Today—more than ever, it seems—you are what you eat. "When it comes to food, people are very opinionated," says Keri Gans, a registered dietitian and spokesperson for the American Dietetic Association. "They decide what works for them and then everyone else should be doing it."

Guys, in particular, get very attached to their meal plans. Unlike their wives and girlfriends, who often schedule outings to clothing stores in support of each other's efforts, men prefer to view weight loss as a blood sport. If there's money—or even bragging rights—on the line, they'll outfast Oprah.

John Durant, 27, went the Paleo route about three and a half years ago after noticing that he'd gained close to 25 pounds courtesy of the steady stream of take-out meals at his corporate-consulting job. After a few months of pastrami for breakfast and grass-fed beef for dinner, he had returned to fighting weight and even his straight male coworkers were telling him how great he looked. Dressed in a black polo shirt, his Equinox gym membership tag suspended from his key chain, he speaks of this transformation as if it were indeed some sort of religious experience. "Everybody these days wants to talk about food," he says. "On a date or at a party, all I have to do is start talking about my diet and I have people's attention for the next hour."

Travis Robertson, a 25-year-old cowboy-boot-clad vegan—or hegan—who hunts birds and deer for sport, is asked to explain his approach every single day, usually right after he pulls out a baggie of dried fruits and nuts. His pals were taken aback by his diet at first, he says. But they came around. Why? Because he could kick their asses. "I lost weight from some of those quote-unquote problem areas," he says. "In the summer, when we're at the lake, you can see a difference."

In this era of slim jeans, celebrity chefs, fitness freaks, and supersize soft drinks, it's easy to see how a guy might become obsessed with the fare on his table. Michael Pollan's Food Rules: An Eater's Manual lists no less than 64 guidelines for supping wisely (e.g., "Don't get your fuel from the same place your car does"). Men's Health's Eat This, Not That! iPhone app dismisses Dunkin Donuts' multigrain bagel with light cream cheese in favor of its more nutritious ham, egg, and cheese sandwich. "People talk about omega-3s," says David Barton, the founder of DavidBartonGym, who recommends a modified version of the Zone Diet. "You go out to eat and they want to talk about where the beef comes from. Is it grass-fed? There may have been a time when it looked fussy to worry about eating organic vegetables, but today it's politically correct."

In the end, there's no clear-cut evidence to suggest that vegetarians live longer than meat eaters or that Paleos are more hearty than hegans, but that doesn't stop the evangelists from championing their diet discoveries. John Durant simply can't resist the urge to ridicule hegans. "Hunter-gathers were serious badasses," he says. "Men who are vegan aren't the most masculine." Travis Robertson nimbly sidesteps the jab, but he does flex his muscles. "You'd never know," he says, "that so many right wing-conservative 25-year-old males are vegans." That's right. You'd be surprised how many men who look just like Tim Tebow eat precisely what Robertson eats.

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