Colin O'Brady, a 33-year-old American adventurer, just became the first person to cross Antarctica alone and unaided.

O'Brady finished his 932-mile, 54-day journey on Wednesday.

His sled, which weighed 400 pounds at the start, mostly contained food, including oatmeal, freeze-dried meals, and special energy bars.

O'Brady said he ate the same items every day in order to consume a total of about 7,000 calories.

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 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 away from his finish line at the Leverett Glacier.

When O'Brady set off, his sled weighed 400 pounds. It contained a tent, a sleeping bag, cameras, a satellite phone, and 30 pounds of fuel for cooking. Most of the sled's weight, however, came from 220 pounds of food — enough to help O'Brady survive for more than two months.

"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.

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.

On December 16, just 10 days before he finished the trek, O'Brady wrote that he had "just enough" food to "hopefully" last until the end. He also noted that he had lost a lot of weight. The 6-foot-tall explorer normally weighs about 165 pounds, but he bulked up to about 185 for this trek. That extra heft and muscle mass did not last.

"My calves feel more like the size of my arms at this point," O'Brady wrote. "My watch is starting to slide around on my wrist and I’ve had to tighten the strap. However I managed another 20+ mile day on these skinny legs."

Read more: An American explorer just became the first person to cross Antarctica alone and unaided. Photos show his spectacular journey.

Colin O'Brady trains in preparation for his trek across Antarctica. Courtesy of Colin O'Brady

O'Brady said in one of his Instagram posts during the trek that accomplishing this goal would not have been possible without a healthy body and mind.

Despite his weakened condition and limited food supply, O'Brady decided to push through the last 80 miles or so of the journey without stopping for more than a meal break or short rest. It took him over 32 hours.

After he finally reached the finish on Wednesday, O'Brady posted a photo of himself calling his wife, Jenna Besaw, with tears in his eyes.

"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."