The 25-year-old did not know about the disorder, and now her family is calling for more restrictions on the diet industry and believe more warnings should be put out in relation to high-protein diets.
According to PerthNow, Hefford's death certificate said an intake of bodybuilding supplements was one of the causes of death.
Her mother, Michelle White, said Hefford had ramped up her gym activity and began a strict diet earlier this year for a bodybuilding competition to be held next month. She was going to the gym twice a day and eating a lot of protein as well as taking supplements.
In the weeks before she died, Hefford told her family she was tired and felt "weird".
"I said to her, 'I think you're doing too much at the gym, calm down, slow it down," White told PerthNow.
White said her daughter's death was a complete shock.
"I couldn't believe what the doctors were telling me, she was dying. I said, 'You have to give her more time,' because she didn't look sick, she looked beautiful," she said.
Hefford, a mother of two, donated her organs and White said she saved four lives.
"Losing Meegan, it's so awful and I still can't believe she's gone but I have to focus on the positives that at least I had 25 years with her and she jammed so much into her life, it's almost like she knew her time would be short," she said.
White said she hoped her daughter's death would encourage the supplements industry to enforce stricter regulations.
She found a number of protein supplement containers in her daughter's kitchen as well as a detailed diet plan.
"I know there are people other than Megan who have ended up in hospital because they've overloaded on supplements," White said.
"The sale of these products need to be regulated."
Health experts said taking supplements was risky, even for people who did not have a medical condition.
Australian Medical Association WA president Dr Omar Khorshid told PerthNow people should stick to a balanced diet.
"I think the problem with the supplement industry is that it's really designed to make money for the companies which sell the products and not to provide any significant health benefit for the vast majority of people taking them," he said.
"This case is obviously tragic and illustrates that you may not know you have a health issue that alters the way you metabolise."
