Until just two years ago, Marcus Wendling had never spent a day sick in bed.
He’d never been diagnosed with anything, never taken a single prescription drug, and didn’t even have a regular doctor.
In May 2023, the father-of-three from Ohio had just completed his first Ironman — a grueling 70-mile swim, bike, and run challenge that only elite athletes even attempt.
But shortly after completing the feat, Wendling noticed small amounts of blood in his stool.
He brushed it off, assuming it was just the toll of pushing his body to its absolute limit — after all, the Ironman is a punishing six-plus-hour ordeal not for the faint-hearted.
Months later, at age 47, Wendling was given a diagnosis that blindsided him: stage three rectal cancer that had already spread elsewhere in his body.
Shockingly, aside from the occasional spotting, he had no symptoms. No pain, no fatigue, nothing to suggest something sinister was growing inside him.
Now, Wendling is speaking out — warning that cancer can strike even the fittest and healthiest without warning, and urging others not to ignore even the smallest signs.
Marcus Wendling (pictured here with his wife Beth), was diagnosed with stage three colon cancer last year, despite living an intensively active lifestyle
The above graph shows the increase in US colorectal cancers in men and women from 2000 through 2021
Doctors across the country are growing increasingly alarmed by a mysterious rise in aggressive colorectal cancers in younger, otherwise healthy adults.
Just yesterday, a new study suggested a surprising possible culprit: a common stomach bug picked up during childhood.
Wendling told DailyMail.com: ‘I was always on top of my health and fitness. I was fortunate to go into this whole thing healthy.’
More shocking was the fact the cancer had been growing inside him despite putting his body under immense physical strain.
Wendling had been juggling his industrial manufacturing company company, hitting the gym six days a week and spent his weekends doing 50-mile bike rides in preparation for the Ironman.
He finished the race in about six hours.
Soon after, in May 2023, he went to the doctor for the blood in his stool. Routine bloodwork came back normal.
His doctor did, however, recommend he get a colonoscopy, in line with the recommended age of 45.
In November 2023 doctors found a large polyp – a growth of abnormal tissue – in his rectum. While polyps can be harmless, they can also turn into cancerous tumors.
Because of the location of the polyp, it couldn’t easily be biopsied or removed with minimally invasive surgery, so doctors remove part of Wendling’s colon in March 2024.
The surgery revealed stage three rectal cancer that had spread to his lymph nodes, small structures that filter fluid throughout the body and help the immune system get rid of threats.
Wendling is pictured here in January with two of his children, Rachel and Sam. He is now cancer free after 12 weeks of chemotherapy
Wendling started chemotherapy about two months after his diagnosis, in May 2024.
After 12 weeks of chemotherapy, he is cancer free, which he puts down to his intensive exercise routine and balanced diet.
He said: ‘I got so lucky. Part of it [surviving] is your lifestyle.
‘We never know when we’re going to face stuff like this, so you want to go into something as healthy as possible.
‘I think that allowed my body to handle the aggressive chemotherapy as best as it could.’
Throughout the entire 12-week chemotherapy regimen, Wendling was still able to work, hit the gym and go for two-mile jogs.
He told this website he had very few side effects from the chemotherapy, with the main one being neuropathy, a type of nerve damage that causes a pins-and-needles pain in areas like the fingers.
He said: ‘Our children are 20, 18 and 14, and we own a company. We have a lot of stuff going on.
‘So to me it was like, “Hey, let’s just power through this and get through it the best we can.”‘
Doctors don’t know exactly what caused Wendling’s cancer, but genetic tests showed he did not have any cancer-causing mutations. He also has no family history of the disease.
Being under 50, Wendling is what’s known as an early-onset case, which is rising in young people.
According to the latest data, early-onset colon cancer diagnoses in the US are expected to rise by 90 percent in people 20 to 34 years old between 2010 and 2030.
In teens, rates have surged 500 percent since the early 2000s.
Lifestyle factors like diet, lack of exercise and sedentary lifestyle have all been blamed, though these causes fail to explain why physically fit people like Wendling have increasingly been diagnosed with colorectal cancer.
Dr Samuel Akinyeye, a gastroenterologist at The Ohio State University Wexner Medical Center, where Wendling was treated, told DailyMail.com these factors cause the colon to ‘lend itself to higher inflammatory states, which is a better environment for colon polyps and potentially colon cancer to thrive in.’
The latest evidence, published earlier this week, suggests childhood exposure as young as 10 years old to a toxin released by E. coli bacteria could increase the risk of colon cancer by triggering inflammation and altering the balance of the gut microbiome.
However, experts are still working to hone in on specific causes for Americans with no known risk factors.
Dr Akinyeye said exploring the role of bacteria is ‘the next step’ to understanding the rise of colorectal cancer in young adults.
Wendling, pictured here with friends, told this website he is looking forward to resuming Ironman competitions and staying active now that he is cancer free
Wendling is now preparing for his next Ironman on May 10 in Florida. It will consist of a 1.2-mile swim, a 56-mile bike ride and a 13.1-mile run.
He is once again off all medications and only has to undergo surveillance scans to see if the cancer grows back every three months.
Though the recommended age to get a colonoscopy in the US is 45, Wendling’s children will have to start when they are 10 years younger than he was at diagnosis, around 37 years old, since they have a direct family history.
For now, Wendling is just focused on beating his personal best and making sure he doesn’t miss his childrens’ sporting events this summer.
‘We’re just full steam ahead now,’ he said. ‘We’re very happy to be living in normalcy.’
