Orthorexia nervosa, a term coined by an American doctor in the late 1990s, describes when a person becomes unhealthily obsessed with righteous eating, the purity or quality of food, to an extent their physical or mental health suffers.

Cutting out fats, sugars, carbs and processed food were common hallmarks of modern diet doctrines.

Butterfly Foundation chief executive Christine Morgan said obsessive eating could be easily hidden and even enabled in the current age where #cleaneating, #sugarfree and #lowcarb posts cluttered the online world.

Ms Morgan said there was typically two ways orthorexia took hold.

"It can be a case of choosing to adopt what you think is a healthy lifestyle and then becoming focused in on it to the exclusion of all else," she said.

"But it can also, for someone with an eating disorder like anorexia nervosa, become a banner under which you hide the fact you are actually restricting food and cutting out food groups."

Ms Morgan said the recent wellness boom and torrent of "health" advice meant food and exercise assumed a focus that was disproportionate to other things in life.

"Our obsession for all things food seems entrenched and there are no signs of it abating," she said.

"It is accompanied with a large range of armchair experts. For those with a vulnerability of tipping into an eating disorder, which manifests in very distorted behaviours around eating and exercise, then it is a minefield to navigate through all of that."

Ms Morgan said it was crucial not to ignore early warning signs such as health deterioration, withdrawal from social activities and feelings of anxiety or self-loathing about food or exercise choices.

The Merrymaker Sisters, Emma and Carla Pappas, said prior to their Paleo diet days they both hit "rock-bottom" on a 12-week strict, fat free, sugar free, calorie counting diet.

The girls lost weight so dramatically their menstruation stopped.

"It actually made our bodies start to shut down, we were so thin, so tired, no energy," Emma said. "We were in a bad place."

The former Canberrans, who began a health coaching business while living in the ACT, decided to end their strict Paleo diet after they noticed how fixated they were about their food and felt an overwhelming stress about maintaining control and sticking to it.

In their "darkest" moments they recall withdrawing from activities that might tempt them to stray from the regime.

"Self loathing and negative body images has been something Emma and I have struggled with since ages 11," Carla said.

"The way we were eating and feeling guilty didn't help that. Alleviating the pressure of not eating a certain way or not being strict allowed self love to come back into my life. I was able to focus on loving myself instead of punishing myself for those guilty feelings for 'falling off the wagon.'"

The sisters said changing their mindset about what was important in life was essential as was remembering that healthy came in all shapes and sizes.