American explorer Colin O'Brady became the first person to cross Antarctica alone and unaided on December 26, when he reached the Ross Ice Shelf.

The 33-year-old skied 932 miles (1,500 kilometres) across the southern continent in 54 days without getting resupplied - which required him to carry everything he'd need throughout the journey on a sled. Everyone who tried to accomplish that feat before O'Brady either gave up or died.

But O'Brady traveled with impressive speed across Antarctica, completing the journey way ahead of his 70-day goal. That allowed him to beat British explorer Louis Rudd, who was also attempting to set the record.

As of Thursday afternoon, Rudd was about 50 miles (8 kilometres) away from his finish line at the Leverett Glacier.

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When O'Brady set off, his sled weighed 400 pounds (180 kilograms). It contained a tent, a sleeping bag, cameras, a satellite phone, and 30 pounds (14 kilograms) of fuel for cooking.

Most of the sled's weight, however, came from 220 pounds (100 kilograms) of food - enough to help O'Brady survive for more than two months.

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"It's a big math equation in that every calorie you add to your sled, of course, adds weight to the sled," O'Brady told Business Insider. "You want the most efficient calories, but in the lightest-weight packages."

Because O'Brady had to keep the weight load as low as possible, his diet sounded rather unappetizing. It consisted of oatmeal, freeze-dried meals, soup, and special "Colin Bars" that his sponsor, Standard Process Supplements, made for him.

There was no space for variety or fresh food during the trek, O'Brady said.

"I literally eat the same thing in the same sequence every day," he said in November.

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O'Brady said he started each day by boiling water for his oatmeal, into which he'd mix protein powder and extra oil as a source of fat. After that, he would eat about 500 calories' worth of the "Colin Bars" every 90 minutes.

Each bar contained a blend of nuts, seeds, coconut oil, and other whole-food supplements. Those were the source of the majority of his energy.

"Every little gram and ounce that I put in my sled has to be worth it, you know?" O'Brady told Business Insider before he embarked on the trek. "There's no playbook to go off of."

In the middle of the day, O'Brady ate ramen with extra salt and consumed a couple servings of veggie protein. Before one of his four freeze-dried dinner options - his favorite of which was chili - the adventurer would also eat four cups of chicken-noodle soup.

The food added up to about 7,000 calories per day, O'Brady said.

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"While the last 32 hours were some of the most challenging hours of my life, they have quite honestly been some of the best moments I have ever experienced," he wrote.

"I was locked in a deep flow state the entire time, equally focused on the end goal, while allowing my mind to recount the profound lessons of this journey."

This article was originally published by Business Insider.

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