A 39-year-old fitness coach mistook her colon cancer symptoms for IBS

Danni Duncan was diagnosed with stage 2 colon cancer at 39 after experiencing changes in her bowel movements, bloating, and extreme fatigue.

Danni Duncan Danni 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 Photography Then, 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.