Danni Duncan was diagnosed with stage 2 colon cancer at 39 after experiencing changes in her bowel movements, bloating, and extreme fatigue.Danni DuncanDanni Duncan, 40, had IBS since early childhood. Her symptoms improved when she changed her diet.When she started experiencing changes in her bowel movements, she assumed it was due to her IBS.She was diagnosed with colon cancer after experiencing extreme fatigue caused by severe anemia.From a very young age, Danni Duncan struggled with IBS symptoms."I remember being maybe around 5 or 6 and really being in so much pain, literally on my hands and knees in the bathroom," Duncan, 40, told Business Insider. She was put on elimination diets throughout primary school and diagnosed with IBS when she was around 11.Duncan, who lives in the Gold Coast of Australia, said she grew up eating McDonald's, frozen pizzas, and Pop-Tarts. As an adult, her IBS symptoms improved as she filled her diet with whole foods and cut back on alcohol. She also began training for marathons and became a fitness and nutrition coach.Duncan, a marathon-running fitness and nutrition coach, was shocked to learn she had colon cancer.Nicole Pas PhotographyThen, in her late 30s, she struggled to go to the bathroom again. She chalked it up to IBS and started taking Metamucil, a fiber laxative, to reduce constipation. She also felt persistent bloating for months after giving birth to her fourth child in September 2024.Eventually, at 39, she was diagnosed with stage 2 colon cancer."It was like I was coming out of my own body," Duncan said. "I kind of giggled and said, 'This can't be true. I'm supposed to live to be 100. That's how healthy I am.'"Severe anemia got her diagnosedDuncan unknowingly had severe anemia, which can be a sign of colon cancer.Danni DuncanWhen Duncan was about 20 weeks pregnant with her fourth child in 2024, her iron levels were the lowest they'd ever been. Even after an iron infusion, her levels remained low. Still, she said her doctor explained it away as a pregnancy symptom and suggested iron supplements.In early 2025, about five months after giving birth, Duncan started training for a marathon that March. She felt winded like never before.Even when she had slept and fueled well, she couldn't get her speed up. Come marathon day, she dropped out of the race when she was three-quarters finished. At the gym, she couldn't finish her sets and experienced dizzy spells in her kitchen.The breaking point was a month later, in April 2025, when she sensed she was going to faint one morning and stumbled onto her couch.Even after having her fourth baby, Duncan couldn't make sense of her extreme fatigue.Danni DuncanA blood test at the doctor's office revealed she had a hemoglobin level of 70 g/L, indicative of severe anemia (a normal level is considered 120 to 160 g/L for adult women). She was scheduled for another iron infusion the next day and a colonoscopy two weeks later, in May 2025, to rule out colon cancer.The colonoscopy showed a tumor in her colon.Duncan, whose 37-year-old friend died from colon cancer the year prior, initially thought of her kids growing up without her. "That thought broke me — I had a tear for a second, and then my mind just switched to like, 'What are we doing?'" Duncan said. "'I have to fight this because I have children.'"Exercising through chemo side effectsDuncan's treatment included surgery to remove the tumor.Danni DuncanLess than two weeks after learning she had colon cancer, Duncan underwent surgery to remove the tumor, including a right hemicolectomy in which part of her colon was taken out. She also had 17 lymph nodes removed outside her bowel wall, the tissue structure that forms the small and large intestines.While cancer wasn't found in her lymph nodes, it was found in the lymph node channels, leading to her stage 2B diagnosis. It put her at higher risk of recurrence because she was closer to stage 3, when the cancer would have officially spread to the lymph nodes. Her doctor wanted her to do four rounds of chemotherapy, considered a standard amount of chemotherapy for earlier-stage cancers, to reduce that risk.Due to the cold sensitivity she developed from chemotherapy, Duncan wore gloves when handling weights at the gym.Danni DuncanShe tried to stick to her routines, including regular walks, light bodyweight exercises, and runs on the weeks she didn't have chemo. Still, extreme fatigue and nausea sometimes wore her down.She also developed cold sensitivity, a common side effect from oxaliplatin, her chemo medication. "Everything seizes up," she said. "Your throat seizes up, you can't breathe; your face seizes up like you're having a stroke." She wore gloves to open her fridge door or hold weights at the gym.The hardest part, she said, was not being able to breastfeed, as chemo drugs can be passed on to the baby through breast milk. Duncan was diagnosed when her daughter was 7 months old and had planned on breastfeeding for far longer."I just loved
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