Will works out most days, driven by a worrying obsession to bulk up his 16st body until he looks like his idol, muscly film star Arnold Schwarzenegger.

“It made me question his commitment to our relationship because I am always second best to the gym,” says Danielle.

Banker Will has been bodybuilding obsessively for the past 18 months.

“I love the buzz and just want to get bigger,” he says.

But Will’s desire to put on muscle has gone way beyond the usual fitness kick.

“Exercise now affects my emotions – if I don’t look massive, my confidence drops and I feel down,” Will, 22, explains.

“Even when I’m exhausted or injured I just train through the pain and tiredness.”

Danielle, a trainee prison warder from Sutton, Surrey, says Will’s addiction to the gym is ruining their relationship.

“When he gets in at night he whips his shirt off and checks his reflection before asking me if I can tell which muscles he’s been working on,” she explains.

“He’s never satisfied. He wants biceps as big as Arnie’s – 17in – and a body like the men he sees in the fitness magazines.

He’s delusional and can’t see how fantastic he looks already.”

Will’s attitude is typical of athletica nervosa – a condition, on the increase in men, which makes sufferers so anxious about their body that they exercise too much.

Alan Currie, psychiatrist with eating disorder charity beat, says: “Athletica nervosa is where exercise is used as a means of body control and people don’t know when to stop.

"The sufferer will see things differently to how other people view them and may not be open to reason.”

Fiona Marley, from Coventry, believes this is also true of her former boyfriend Liam Moynihan, 30, a personal trainer, model and actor.

The 21-year-old university student split from Liam 10 months ago, finding it impossible to have a normal relationship with a man whose life was dominated by
his quest for the perfect six-pack.

She said: “We could never go out for a whole day.

"I’d say: ‘Let’s go to Blackpool to the beach, let’s go to Manchester to the shops’, but he refused to miss a workout.

“He hardly drinks so we couldn’t go to the pub either.

"If he had a photo shoot coming up it would be even worse.

"He’d cut out carbs or fast completely and even reduce his water intake so his abdominal muscles had better definition.

"But the lack of food made him moody and difficult.

“Even when he didn’t have a modelling shoot, he was still obsessive, taking photos of himself on his mobile after having a spray tan.

“In the end we parted because his heart was set on training, not romance.”

Liam says: “Fiona couldn’t accept how important exercise is to me but I’d go mad if I couldn’t go to the gym – I get really agitated if I miss a day.

2My body image can change completely within just 24 hours.

“I go from looking OK to looking awful.

2When I flick through fitness magazines, I feel a million miles away from where I want to be.

2But I’m not obsessed, I’m dedicated.

“Fiona’s right, though, there is a pattern to my behaviour.

"She’s the fifth girl who has left me because of my training.”

Last month a study by psychologists at Winchester University proved that the more magazines a man reads, the more likely he is to suffer from athletica nervosa.

So while many men work out to try to attract a girlfriend, they may find their obsession destroys the resulting relationship.

It’s a lesson Will may soo"n learn.

As Danielle concludes: “Ultimately I will say enough is enough – a relationship just can’t survive when exercise is more important to a man than his lover.”

Is your man obsessed with the gym? Does he worry more about his weight and appearance than you? At what point does a healthy attitude to fitness become a dangerous obsession? Would you let it compromise your relationship?

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Photography: Giles Park Hair and Make Up: Sadie Hewlett at Time Styling: Nana Acheampong