"Identification and timely treatment is key to successful outcomes. The success of treatment is reduced with the duration of the eating disorder."
Dr Mackersey said eating disorders could be resistant to treatment after they had been established for a few years and chronic eating disorders tended to have a pattern of relapsing symptoms.
If a person suspected someone had a eating disorder, Dr Mackersey said the first step was to talk to the person and try to convince them to see their GP.
"It is common that people with eating disorders do not want assistance and do not want to hear the concerns of others. There are many reasons for this such as embarrassment or a fear of gaining weight."
Food Solutions owner and dietician Fiona Boyle helps treat eating disorders alongside psychologists.
"If you are worried about a young child that might be displaying signs, one of the key things is to get assistance as early and quickly as possible."
Mrs Boyle said there were a number of warning signs. These included changing their eating patterns - for example they may choose to start following a vegetarian diet then begin restricting other foods, introducing food rules such as sugar free, eating less than normal, obvious weight loss, talking about certain body parts they are not comfortable with, not wanting to eat takeaways with the rest of the family, or getting busy around meal times.
"Their whole personality can change because they are not feeling particularly well and they are trying to fight the messages in their head so they become withdrawn. They can suffer from depression or become more irritable."
Mrs Boyle said treatment was often a two-pronged approach, with psychological help and advice from a dietician about healthy living and what is normal.
Good Talks director Rachel Hansen, who teaches workshops with groups of people about how to love and trust your body, said she looked at what fed into an eating disorder with her groups.
"With the increase of social media and things, we've become a far more visual society. Of course, with photos, the quickest and easiest critique on someone is their physical beauty or lack of.
"For this generation of teenagers, there's a really big increase in the focus on how you physically look and, with the rise of selfies and things, teenagers spend a lot of time editing photos of themselves before showing them to the world."
Ms Hansen said it was easy for teenagers spending all that time critiquing images of themselves to get into a space of self doubt, especially if the teens were comparing their own photos to ones in magazines or of celebrities paid to look good on social media.
She said many young girls did not realise how people with big social media followings manipulated and edited their photos to portray a certain image.