When Nick LaCava settles into his boat on Saturday morning, for his first race of the London 2012 Olympics, he'll be facing a physical obstacle that's unusual among elite athletes, at least outside of combat sports. The American lightweight rower will have spent the preceding days sucking weight, whittling his 6'3" frame down to a meager 156 lbs. Not quite Christian Bale in The Machinist, but close enough.

Rowing is a sport that demands both sheer strength and endurance, and competitors in lightweight events — which require that each crew average 154 lbs per rower, with no single member exceeding 160 lbs — are tasked with the contradictory aims of building the strength and resilience of a Viking while maintaining a slender, fat-free body. By way of comparison, competitors of a similar stature in heavyweight rowing events (which form the majority of the sport) weigh in at around 205 lbs.

As the tallest lightweight on this year's U.S. squad, LaCava has it the hardest. "When you're really light, you don't recover as fast, and you're more prone to injury," he explains. "There's a mental component, too. You can get really stressed and unhappy when you're trying to cut weight."

How does he manage it? LaCava says that while he's always watching his diet, he spends most of the year above his 156-lb competition weight. Leading up to a regatta, he'll shed every spare pound from his frame.

"Everyone has their own crazy diet for cutting weight, but really it's simple: You have to use more calories than you take in," says LaCava. He structures his meals around training sessions, making sure to eat right before and right after each workout. He eats a lot of lean protein and piles of green vegetables, and cuts out sweets (his weakness) and other carbs.

On race days, LaCava will sweat out those last couple pounds and abstain from food and water before weigh-in. "As soon as you weigh in, all you want to do is stuff your face full of food, but you need discipline. Otherwise, all the blood will go to your stomach during the race." The main focus right before the race is rehydration.

"The toughest is when you have back-to-back races," says LaCava. "Because even after your race, you have to manage your weight, or else you won't make weight the next day." The Olympics will be better, because he can indulge in a hearty post-race meal and has a day in between races to get his weight back down.

Below is a sample of what LaCava eats on a typical training day, during which he'll row for three to four hours. No 12,000-calorie, Michael Phelps-style feasts for this guy.

Pre-workout breakfast:

Bowl of cereal

Post-workout breakfast:

Two eggs

Oatmeal

Yogurt

Fruit

Lunch:

Turkey sandwich with Swiss cheese and lettuce

Carrots and spinach

Midday snack:

Banana

Clif Bar

Dinner:

Pasta

Grilled chicken

Salad with kale, spinach, carrots, mushrooms

Ice cream

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