Christine Cronau thought she was living a healthy lifestyle - she was a vegetarian, followed a low-fat diet and had slimmed down.
But by age 30, Ms Cronau had been diagnosed with chronic fatigue.
"I thought I was just doing the hard yards as a working mother, and that everyone sort of felt like that," the mother-of-two said about feeling continuously exhausted.
When Ms Cronau became pregnant with her first child, she decided to become as healthy as she could. A few years down the track, she altered her eating habits again with the aim of being "super healthy".
She became a vegetarian and her meals consisted of wholegrains, unrefined foods and little fat.
"I always ensured that I combined my grains and legumes so that I was getting enough protein. Unfortunately, instead of my health improving, it started to decline," she said.
There were no obvious signs that things weren't quite right.
"You don't realise it until it becomes quite bad and then you realise that there's something wrong," Ms Cronau said.
When she was diagnosed with chronic fatigue, she learned that her "healthy" diet was in fact doing her damage.
"What I thought was healthy food was actually making me sick," she said.
"Even though I was combining foods, my blood tests showed that I was severely protein-deficient. I was losing calcium from my teeth and bones, and I was only in my late 20s."
When people are diagnosed with chronic fatigue, the amount of oxygen patients are getting into their blood cells is measured, Ms Cronau said.
"The guy who diagnosed me said, 'If you had just run a marathon your (oxygen) levels would be 20 or so and then they'd come back up to a normal level of 80,' and my levels were 19 all the time.
"So it was like I had just run a marathon all the time."
Australian Medical Association Council of General Practice chairman Brian Morton said sufferers of chronic fatigue experienced tiredness over a period of at least three months.
"It's a tiredness, weariness, physical fatigue that is more severe and chronic than one would expect from perhaps a simple infection," Dr Morton said.
He said there were theories about how people got chronic fatigue but some researchers said it could be caused by viruses such as glandular fever.
No one had been able to prove the cause and effect, he said.
Dr Morton said there was no specific treatment for chronic fatigue, but a good diet could help.
He said treating associated medical problems was a step in the right direction.
"If you're chronically fatigued then you're likely to become depressed," he said.
"People usually do respond well with antidepressants and it's not to say chronic fatigue is purely in the mind because we don't know and people's symptoms are different to just pure depression.
"But they will also benefit from a reasonable diet.
"If there are abnormalities in the diet maybe that does predispose to chronic fatigue syndrome."
Ms Cronau, now 40, credits her nutritionist for getting her back on track to a healthy lifestyle.
"He explained that fat is an essential nutrient and what we've all done these days is cut fat out of our diet," she said.
"So really, a lot of us are running on empty because it changes the pH in our bodies and then we become sick.
"A lot of people think that fat causes heart disease when in actual fact it's sugar and all the processed carbohydrates (we eat).
"If we are able to grow it then that's a healthy food, whereas if you go into the supermarket and buy a loaf of white bread, that's obviously not something we were designed to eat."
Ms Cronau said eating natural fats such as butter and coconut oil was essential for people's diet.
"So when we actually cut those out - and they're normally replaced with carbohydrates or sugar - it really upsets the balance of our body," she said.
Brisbane-based Ms Cronau describes chronic fatigue as the burning of adrenal glands (which develop hormones and are affected by intense stress).
To deal with her lack of energy, she eliminated all sugar from her diet and cut down on carbs. She also reintroduced natural healthy fats. Her symptoms disappeared, she said.
Now Ms Cronau is a second Dan black belt in Rhee Tae Kwon Do and has "loads of energy". She has also written a cookbook, based on 10 years of research on nutrition.
"I wasn't satisfied to eat boring foods for the rest of my life and I didn't want my children missing out because I cut sugar out, so I developed simple, easy recipes for all my favourite foods," she said, listing chocolate, ice cream and cake.
She said the cookbook, Great Health is a Piece of Cake, was the result of her diagnosis of chronic fatigue.
She touts it as an expose about dietary truths that have been ignored in the food industry.
Throughout the pages are simple recipes for dishes such as apple pie, corn chips, sushi, roast turkey and mayonnaise. She also lists foods people should avoid (including soy), foods to eat (unprocessed raw butter) and tips for maximising health.
Ms Cronau said people did not have to skimp on delicious foods to be healthy.
"That's the biggest concern for a lot of people; they don't want to miss out on their favourite foods and they also don't want to be deprived and hungry, which is what happens when you go on a diet," she said.
"What I've tried to do is make a substitute for just about any type of food, including chocolate ... so you can certainly have everything."