Dan Benintendi

Dan Benintendi (Brandon Thibodeaux, For the Chicago Tribune / April 26, 2012)

"Dan was a guy who could barely walk a few blocks before the surgery," Kim said. And while surgery helped make Benintendi's transformation possible, it also created two new realities that needed tending to.

Endurance athletes need to consume thousands of calories a day in a carbohydrate-rich diet to replenish glycogen in their muscles, and they need adequate hydration to make up for sweat losses and avoid dehydration. But the typical gastric bypass patient is advised to eat very small meals and not drink 30 minutes before or after eating to avoid overloading their tiny pouch.

It takes time to acclimate the body and pouch, and Benintendi, like any gastric bypass patient, said learning what his new stomach liked and didn't like was a matter of trial and error. Though he needed more carbs for more intense exercise, it took a while to get used to bread, pastas and other carbs that fuel his sport. "Now (Dan's) body's adjusted, and he's gradually increased his caloric demand and the absorption of the calories and nutrients he needs," Kim said.

"The way I do it is to eat all day," said Benintendi, who takes in 4,000 to 5,000 calories a day over nine to 10 meals. "I eat tons of grains and nuts, veggies and good proteins and fats, a good variety of foods, but I still have to eat for fuel and workouts so it's a constant grazing thing — plus my stomach's a little bigger now, the size of a tennis ball."

"You have to be strategic. I eat every hour-and-a-half to two hours, so it's a challenge, but I make it work for me.

"I take in the same stuff as other athletes — gels, Cytomax, Gatorade — I can pretty much tolerate anything when I'm training. If I'm sitting at home and eating something with a lot of sugar, it can give me a problem, but when the body's burning its glycogen stores, I can tolerate the high concentration of sugar better without gastric distress."

On his successful 104-mile run, for example, he ate everything from cookies to pizza to a vanilla shake — all in small doses.

Another post-surgical reality involves managing the excess skin resulting from extreme weight loss. For Benintendi, "he'd strap all the skin in when he did his races," explained plastic surgeon Dr. Ghada Afifi, who last year removed 11 pounds of skin from Benintendi. "I've operated on a lot of people who've become athletes after losing 100-plus pounds, and they need to have that skin removed because it interferes with their efforts."

Today, Benintendi is 6 feet 2 and weighs 215 pounds. His body fat measures just 11 percent, down from his pre-surgery measure of 59 percent. He says his relationship with food has changed.

"The thought of how it tastes is secondary," he said. "I think about what food will do for me. If I'm going to take a week off I dial down the food, and I'm OK with that; I'm running my life rather than letting my life run me."