On the morning I was to speak with Jeffrey Weiss about his 2025 memoir, Racing Against Time: On Ironman, Ultramarathons, and the Quest for Transformation in Midlife, I willed myself out of bed and went to the fitness center to swim.

Because that’s what Weiss would do.

Racing Against Time chronicles Weiss’ fitness journey, tracing his evolution from high school and college tennis to powerlifting, then eventually marathons, Ironman Triathlons, and ultramarathons well into middle age. It’s the story of how physical training has transformed his life—and how the dedication and discipline required to reach ever more ambitious goals have shaped him both personally and professionally.

Kirkus Reviews praises Racing Against Time as “a motivational sports memoir…. Running throughout the text is a clear sense of Weiss’ spirit of adventure, resilience, and iron will, which he drew upon while pushing toward his next milestones.” The book builds toward the ultimate milestone, the punishing 72.2-mile Tahoe Midnight Express ultramarathon, in which Weiss notes the possibility of contending with issues other than stamina:

With only two days to go, the race director held a Zoom orientation. During the call, I learned there actually are bears out there. I had thought the reference on the website to not feeding the bears was just a joke. The director assured us, however, that they are not dangerous. They might charge toward you and pretend to attack, but they would not actually do that. They just wanted food. Of course, I would be running with a backpack loaded with gels and snacks, which certainly seemed like food to me, but if the organizers weren’t worried about it, I decided, I shouldn’t be either.

If there’s one lesson Weiss has taken from his decades of training, it’s that pushing physical limits is ultimately an exercise in discovering one’s hidden potential. “We are capable of surprising ourselves,” he says.

He recalls a time when he thought otherwise. “Before I became serious about running, I told a friend that I was as likely to run a marathon as I was to walk on the moon,” he says. “I’m on the large side from my powerlifting days, so I don’t have a traditional runner’s body. If you’d asked me when I was 17, 25, 30, 40, or 45, I would have said there was no way I could be a serious runner. But fundamentally, I persisted and found I could do longer and more challenging races.”

The turning point came when he was 48, the year his father died. From his father (a patent lawyer) and his mother (an immigration judge), he inherited not only a strong work ethic, but also a commitment to education. As with his fitness regimen, he took the latter to an extreme, earning undergraduate and law degrees and two master’s degrees in international law and biotechnology.

But his father’s passing was “very much a reminder that I was getting older,” he says. “Life is finite. I was approaching 50, and I wanted to age in the way that would make me the happiest.”

He ran his first 10k as an adult that year, in part to erase what he called a “previous failure” when he attempted to run a 10k when he was 17 and walked the last two kilometers. “That always gnawed at me,” he says.

Fitness has always been a big part of Weiss’ life. When he stopped playing tennis, he became immersed in powerlifting. But life happens. “When my former wife and I had kids, I fell out of the practice of exercising six to seven days a week,” he says. “I missed it. It was always in the back of my mind [that] I should be exercising regularly. But I had a family and professional responsibilities, and I told myself that it was just not the right time. After my father died, I realized that the time was now, and there was no more putting it off.”

Running isn’t the only arena in which Weiss has set ambitious goals. He left a private law practice in 2012 to become an executive of a startup that sold in 2023 for $3 billion. He recently joined another startup.

Weiss, who lives in Tel Aviv, doesn’t consider himself a full-time writer. “I am a writer who is interested in becoming a better one,” he says.

Writing was another in a series of goals he was determined to achieve. He says he’s always been a reader. “In high school, I’d become interested in a particular subject and read everything I could find about it. That prepared me to write nonfiction.”

Weiss has a writing regimen. “I write for an hour, six days a week,” he says. “I’ve been doing that for years and years. I find a subject that’s interesting to me and that I would want to read a book about. Then I think, ‘Maybe that’s a book I should write.’”

His first book was I Am My Brother’s Keeper: American Volunteers in Israel’s War for Independence 1947-1949, which is about North Americans of all faiths who fought with Israel in its war for independence. His second was Fighting Back: Stan Andrews and the Birth of the Israeli Air Force, the biography of an assimilated Jew and World War II veteran who became one of the Israeli Air Force’s first fighter pilots.

While Weiss was inspired by several books about running, fitness, and health (among them Chris Crowley’s Younger Next Year, Carol Dweck’s Mindset, and Rich Roll’s Finding Ultra), he thought there might be value in his own story. “Part of it was wanting to pay it forward for people who were just getting started” on their own fitness journeys, he says. “And I’m a sucker for the classic American story that moves toward something hopeful and has a happy ending. I felt that if I was able to finish ultramarathons at my age, there was something encouraging in my story.”

Weiss also doesn’t consider himself a fitness evangelist. “I try to encourage people to take fitness seriously and make it a regular part of their lives,” he says. “Extreme sports gave shape and direction to the way I approach training, and I like that focus. But not everyone needs or wants that. It’s just a part of my life. My days are enriched by it. We live in a time when there’s a focus on longevity, and regular exercise absolutely will extend that period of your life in which you’re able to do the things you love, whether it be hiking, skiing, walking around the block, or holding grandchildren.”

Weiss, 64, loves that he’s still in motion. He’s scheduled to run the Chicago Marathon in October. “I do hope people take away from Racing Against Time that regular exercise can have transformative effects on us. We tend to place limits on ourselves. We think, ‘I could never do X.’ It’s good to challenge yourself and ask, ‘Am I selling myself short?’ If you approach fitness the right way, it’ll change what you think you’re capable of. It doesn’t mean you’ll always succeed. I had two big races I wasn’t able to finish, but you learn how to draw lessons from those experiences and stay positive and find other challenges. That’s a good way to live life.”

Donald Liebenson is a Chicago-based writer who is published on vanityfair.com and in the Washington Post and other outlets.