The first time a bloke at the gym offered to buy Drew Harrisberg’s insulin from him, the exercise physiologist assumed it was a one-off encounter with a foolish fitness freak.

But when it kept happening, with countless others willing to pay a pretty penny for the syringes that keep him alive, the Sydney sports scientist made a disturbing discovery.

“There’s a growing number of men who are looking for any way to get extra muscle on their frames, and they’ll do just about anything to achieve it,” Mr Harrisberg, who was diagnosed with type 1 diabetes when he was 22, told news.com.au.

“Insulin is the most anabolic hormone in the body, and so they believe that by injecting it, they’ll bulk up. I’m asked often to sell it. It’s crazy.

“Everyone has insulin anyway. The idea that having extra will make you even bigger is just so silly and so dangerous. You don’t need to inject it — you’ve already got it.”

Mr Harrisberg has seen people in possession of insulin needles and even on occasion witnessed someone injecting it.

“The obsessive ones talk about it a lot. It’s fatal at the wrong dose. It can kill you in minutes. It’s so potent and powerful,” he said.

The news this week that a young man from New South Wales died from caffeine toxicity, after unknowingly ingesting a small but fatal amount of pure caffeine powder, has shone a light on supplements that are growing in popularity in fitness circles.

Lachlan Foote, who was 21 when he died, wasn’t a regular gym-goer, but mates bought and shared around protein and caffeine powder.

He had no clue how potent the latter was — experts say very few people who use pure caffeine know how dangerous it is. Mr Foote died on the bathroom floor of his family home after collapsing.

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Pure caffeine is one of a number of powders used by a growing cohort of the image-conscious and fitness-obsessed gym population.

Walk into the locker room of just about any gym and you’ll see groups of musclebound blokes chugging down protein potions and sharing powders with each other, Mr Harrisberg said.

But this isn’t just the domain of competitive bodybuilders. The supplements obsession has bled over into the mainstream, he said.

“What bothers me about all of this is that obsessive bodybuilders are literally willing to do anything. I think we’re losing what it means to be healthy, actually healthy and not just muscular,” Mr Harrisberg said.

“The supplement obsession is no longer just for the obsessive bodybuilder trying to win trophies at competitions. The everyday gym-goer is so into it. I don’t know how it happened.”

It’s that normalisation of muscle obsession that is helping to drive a boom in steroid demand, authorities say.

“The majority of steroid users in Australia, the UK and other countries around the world are motivated by physical appearance,” Scott Griffiths, a male muscle dysmorphia expert at the University of Melbourne, said.

“Simply put, contemporary steroid users want to look better, feel more confident and feel more attractive. Consequently, more users than ever are at risk of developing body image and eating disorders, including anabolic-androgenic steroid dependence and muscle dysmorphia.”

Jane Fitzpatrick, a sports and exercise medicine physician and an associate professor at the University of Melbourne, said fitness supplements were totally unregulated.

“You don’t really have manufacturing standards, and as a consequence, the supplement you buy could contain ingredients not on the outside of the packet or different concentrations,” she said.

Professional athletes are increasingly warned to steer clear of supplements — even popular brands — due to the potential for contamination.

And that contamination could extend to trace amounts of anabolic steroids, Dr Fitzpatrick said.

“That doesn’t necessarily make them unsafe as such. It certainly makes them inappropriate for an athletic population subject to anti-drug protocols.

“In recent times, the number one cause of a returned positive drug test in an athlete in Australia has been supplements use. In most cases, the athlete wasn’t aware that there was something of concern.

“We educate our athletes that most supplements should be regarded as contaminated.”

A growing trend among fitness enthusiasts is the do-it-yourself approach to supplements, Deakin University nutrition science expert Shaun Mason said.

People buy a number of powders, pills and potions marketed as beneficial to workouts and muscle gain and make their own concoctions, Dr Mason said.

“It’s cheaper to buy in bulk and make your own. It’s readily available over the counter or online. People might share it among friends,” he said.

The widespread use of highly caffeinated pre-workout products is of concern to sports science and health professionals, he said.

“When it comes to gym training and exercise, caffeine is one of those compounds that has been shown to have potential performance benefits. That’s across a range of sports, from short and intense activities to long endurance activities,” Dr Mason said.

“The risk of pure caffeine is that it’s so easy to overdose. If you’re putting an unmetered amount in a drink, that’s a potentially toxic dose.

“It’s cheaper to buy in bulk and make your own. It’s readily available over the counter or online.”

Mr Harrisberg said he wouldn’t touch pure caffeine because he’s aware of how dangerous it is in even small doses, but he’d seen its popularity first-hand.

“Pure caffeine obviously gives a stimulant effect, it makes people feel pumped up for the gym. A lot treat it as a fat burner,” he said.

“People make their own cocktails with various ingredients and it gets even more dangerous.”

Dr Fitzpatrick said the average person had a perception caffeine was totally safe.

“Therefore, if someone is using pure caffeine they might assume that a little bit more (than recommended) can’t be that bad. The problem is the concentration in a teaspoon. It’s enormous, and it’s rapidly absorbed all at once,” he said.

Following Mr Foote’s death and reporting this week about the findings of a coroner’s report, the Government has ordered a review into the sale of pure and high caffeine products in Australia.