Joining the ranks of anorexia nervosa, bulimia nervosa and binge-eating disorders now is "orthorexia nervosa", a form of compulsive "righteous eating" bordering on paranoia.

It could take an extreme form of raw food eating that aims to "align bodies, minds and souls" by feasting on "cleansing and immune-boosting" raw foods which retain enzymes.

Or, a clean food regime with no gluten, dairy or sugar. Or, food recipes to cleanse the gall bladder.

Increasingly seen among health professionals, yoga masters and performing artistes in the West, this obsession of eating healthy becomes an eating disorder when orthorexics become fixated on food quality and purity.

What and how much to eat, and how to deal with "slip-ups" and accompanying guilt make life difficult for followers, often isolating them from society and even family members.

The objective, besides the obvious one of good health, often covers compulsion for complete control, improving self-esteem, search for spirituality through food, and using food to create an identity.

Self-esteem is closely tied up with the diet and the practitioners sometimes feel superior to others.

So how does one recognize the symptoms, when it is a thin line between healthy eating and orthorexia nervosa?

If thoughts about food worry you for more than three hours a day, or if you feel guilty when transgressing your healthy eating rules, then chances are that you are on the road to orthorexia, if not already there. Your eating behaviour will result in distress and health issues.

Orthorexics can be plunged into gloom by digressing from strict eating tracks and feel guilty after eating a piece of bread.

They become anxious about when their next carton of kale, chia or quinoa hit is coming, or eat only at home where "superfood" intake can be tightly controlled, writes The Conversation

An Italian study found prevalence of orthorexia nervosa of 57.6%, with a female-male ratio of two-to-one. Similarly in some other cities.

A form of OCD?
There is a growing debate on whether the disorder needs to be clubbed with already classified ones such as anorexia nervosa and bulimia nervosa, or treated as a distinct one.

Clinicians arguing that orthorexia nervosa be recognised as a separate eating note distinct pathological behaviour, including a motivation for feelings of perfection or purity rather than weight loss, as in other disorders.

Some agree that orthorexia has elements of OCD (obsessive compulsive disorder).

It was American doctor Steven Bratman who coined the term "orthorexia nervosa" in 1997 after emerging from a brief tryst with the disorder himself.

Describing his experience in a commune in upstate New York where he developed an unhealthy obsession with eating "proper" food, he says the "need to obtain meals free of meat, fat, and artificial chemicals had put nearly all social forms of eating beyond my reach. I was lonely and obsessed".

If this is a disorder, can it be cured?

Yes it can but first, the orthorexics must first admit there is a problem, then identify what caused the obsession.

This will involve working through underlying emotional issues.

While orthorexia is not a condition the doctor can diagnose, recovery requires professional help often, say experts.