The mirrors bolted to the walls of Sydney's bodybuilding gyms are crowded with impossibly muscled men. It's a smorgasbord of peak health and physical perfection.

But Joey Sheather can pick them. The men who have bulked-up too fast, whose passion for fitness has tipped over into obsession. The ones who will never be satisfied no matter how hard they shred or how much body fat they lose.

Their muscles are not just physical shows of strength. They are an attempt to forge emotional armour, says Sheather, a veteran personal trainer at Camperdown Fitness.

"These guys are trying to fix their feelings of inadequacy by building their physiques," he says. "They throw themselves into physical activity to have something to focus on other than those painful thoughts."

Muscle dysmorphia is anorexia's burly counterpart. It's the body dysmorphic disorder known as "bigorexia" that predominantly affects men.

People with muscle dysmorphia are consumed by an obsession that they are too small or underdeveloped and may take drastic and damaging steps to bulk-up, such as compulsively exercise, harmful diets and anabolic steroid and peptide abuse.

"It's very obvious," Sheather says of the increasing number of scrawny men whose bodies erupt with the rippling muscles of seasoned body builders with seemingly negligible effort.

The use of performance and image-enhancing drugs (PIEDs) doesn't necessarily point to muscle dysmorphia, and not every individual with muscle dysmorphia uses PIEDs. But researchers says the rising rates of PIED use of is the canary in the coal mine of an emerging public mental health issue.

"You get clients who might achieve something really positive, whether it's a strength goal or body fat loss, but all they are focused on is picking at the negative," Sheather says.

His job has become part personal trainer, part counsellor as he watches the increasing creep of muscle dysmorphia among his clients and more broadly among the growing culture of hulking masculinity on the gym floor and online.

"I had a client who was very unhappy and struggling emotionally. He had a very tough childhood and always felt isolated. He came to the gym to build himself a fantastic physique but he would go through some really down, really dark times."

One day, instead of training, Sheather pushed the young man into his office where a life coach counsellor was waiting for him. "We didn't train that day. It was the best thing I could do for him," Sheather says.

Sheather says he is often left emotionally exhausted after an endless procession of clients "mentally unload".

"We still train but often it's more important to them that I just listen and support them as they pour their hearts out," he says.

The changing shape of eating disorders

As Scott Griffiths sat in his undergraduate lecture on eating disorders, incongruous images of the burly acquaintance at his local gym muscled their way into his thoughts.

"The lecturer described how people with anorexia would [invariably] obsess about their weight, exercise compulsively, run flat-out on the treadmill, worried about what they ate and abuse laxatives and diuretics.

"The guy at the gym was different, but then not so different," Dr Griffiths says, now a National Health and Medical Research Council early career fellow.

He obsessed about his protein intake and muscle mass. He wasn't running on the treadmill, he was lifting weights and instead of abusing laxatives his drugs of choice were steroids, says Griffiths.

Then it clicked.

"Not all eating disorders are about thinness," saysGriffiths.

Modern eating disorders are often intrinsically fused with body-image issues. The coveted body type du jour for men is not a slender frame, but the opposite.

"If you're a young boy chances are you would describe your ideal body as muscular," Griffiths says ahead of his Sydney TedTalk: 'muscle dysmorphic, the make eating disorder'.

The title of the talk is a misnomer, Griffiths says, acknowledging men were diagnosed with anorexia and bulimia and women could also develop muscle dysmorphia, most notably within the bodybuilding culture.

But the stereotype of a young teenage girl starving herself to thinness is a myopic understanding of the chimeric life-threatening conditions.

Muscle dysphoria is the latest manifestation of eating disorder to rise from an image-obsessed Western culture that covets the muscled male physiques of blockbuster superhero franchises, pop stars and #fitspo Instagram feeds.

For every Arnold Schwarzenegger and Jean-Claude Van Damme movie of the '80s, there are now thousands of muscle men on social media posting daily videos and images of their rippled bodies.

"You can access a huge slew of idealised bodies to compare yourself to and that critical voice in your head that says 'this is probably not real' is often conspicuously quiet," says Griffiths.

He believes the forms eating disorders will take in the future will be dictated to a large extent by how greatly future societies value physical perfection and their new barely attainable ideal. "It has changed in the past and it is likely to change in the future. We have to be vigilant about new eating disorders that will turn up," he says.

On the timeline of eating disorders, muscle dysmorphia is in its infancy.

The first case studies of anorexia were reported by British physician William Gull in 1873. His most cited case study was a young woman, but Gull also identified a man with anorexia.

Body image was not a factor in the first documented cases. They were linked to piousness, a devotion to god and casting out worldly impurities, drawing some uncomfortable parallels to the modern phenomenon of orthorexia spurred on by extreme the "clean eating" and "wellness" industry.

Muscle dysmorphia has only been described in any great detail in the last 20 years. US researcher Harrison Pope, whose book The Adonis Complex was published in 2000, detailed what we called the male body image crisis.

The fraught diagnosis

People with muscle dysmorphia are often diagnosed with the catch-all EDNOS (Eating Disorders Not Otherwise Specified). The Diagnostic Statistical Manual (fifth edition) the psychiatric bible, listed it as a subtype of body dysmorphic disorder. Like other eating disorders, depression, anxiety and other mental illnesses often piggyback the condition.

But sceptics say the diagnosis is a fad.

"I sympathise concerns that psychiatrists and academics more generally are finding new ways to pathologise what is essentially a broad and diverse, normal array of human experience and behaviour," Griffiths says. "But after working with guys with muscle dysmorphia and with the rising rates of steroid use, this is showing all the signs of being a serious condition."

Some researchers claim muscle dysmorphia may be as common as anorexia, yet there is no good data to support this. "The burden of body image still disproportionately affects women and girls," Griffiths says.

But rising steroid use in Australia suggests muscle dysmorphia is more than an "aberrant curiosity". It's an emerging public health problem, he says.

Between 2000 and 2009 the proportion of all injected drug users in Australia who reported that the last drug they injected was steroids or other performance and image-enhancing drugs was 1 per cent. By 2014 steroid use had jumped sevenfold, a Kirby Institute report found.

Since 2011 steroids have been the number one drug of choice for new injection drug users in Australia, a practice that is still growing among new drug users.

"These rising rates makes it almost certain that muscle dysmorphia is increasing as well," Griffiths says.

A large population-based study by Macquarie University researchers found the prevalence of eating disorder behaviour including vomiting and dieting was increasing faster among men compared to women between 1998 and 2008. A separate study found 15 per cent of males had marked dissatisfaction with their bodies compared to 33 per cent of females.

Perfectionism becomes pathological

Perfectionism was a common trait among patients.

"People who are very driven, very meticulous are prone to falling into those habitual, obsessive patterns of dieting and exercise that are the hallmarks of these disorders," Griffiths says.

Some research suggested bullying and a fraught family environment were also risk factors, much like other eating disorders, as well as the need to exercise control over one's body to ease feelings of helplessness. Like other eating disorders the patients were at risk of severe physical as well as mental distress.

Prolonged steroid abuse could severely damage the endocrine system and cause infertility, and the risks associated with peptide use are a largely unknown. There was also evidence suggested muscle dysphoria was linked to high suicide rates.

A recent study found men with body image issues were four times more likely than women with eating disorders to go undiagnosed.

There is no good data on recovery rates among people with muscle dysmorphia, or gold-standard research on the success of treatments. But Griffiths says treatments recommended for other eating disorders including cognitive behaviour therapy and family-based therapy for younger patients was proving to be effective.

"It's a real battle to get guys to come forward," Griffiths says."Body image is stereotypically seen as a female problem and talking about mental health concerns is already discouraged by traditional masculine [culture] ... A big part of getting these guys help is trying to convince them that muscle dysmorphia is real.

"If you have the gym as a hobby and it's good for you and you genuinely feel good and accomplished about yourself, then more power to you. Absolutely don't change what you are doing and no good psychologist will cajole you," he says.

"But have an honest look at how you feel when you miss a training session or break your diet. Is it something you bounce back from in five minutes or does it wreck you for a week?"

Dr Scott Griffiths will appear as part of TedX Sydney 2017 on June 16.