Boyzone in the buff: Irish boy band reveal their toned bodies at reunion gig

In a bid to outdo their reunited rivals Take That, Boyzone have spent weeks in the gym getting in shape for their comeback tour, which kicked off in Belfast on Sunday night.

Their hard work obviously paid off after their first show of their UK comeback tour opened to rave reviews.

Full Monty: Boyzone show off their newly-toned bodies in a homage to the classic British comedy.

The Dublin-born singers are now married thirtysomething fathers compared to youthful teenagers when they were first put together by X Factor judge Louis Walsh in the early 1990s.

But because they are older, their fans are too, meaning they can push the boundaries with their raunchy stage show.

To promote their comeback tour, the group showed off their six packs in a homage to the 1997 British comedy Full Monty for this week's Heat magazine.

Reunited: Boyzone take to the stage after an eight year hiatus at the Belfast Odyssey Arena

At the city's Odyssey Arena on Sunday, the quintet started the show in boyband trademark  white trousers and knee-length jackets, before changing into a tight trouser and skimpy t-shirt combination, which showed off their newly-toned bodies.

The high-energy show involved the band - comprising of Ronan Keating, 31; Stephen Gately, 32; Mikey Graham, 35; Shane Lynch, 31; and Keith Duffy, 33 - dancing on treadmills and writhing around with scantily-clad female dancers.

The Belfast Telegraph declared the gig a success after witnessing the delighted response of thousands of screaming fans.

Clinch: Ronan Keating gets to grips with a sexy female dancer

The Telegraph's Patricia McDonagh wrote: " The pain of the past was well and truly put to bed during the sell-out concert in front of thousands of screaming fans at the Odyssey last night, the first of their Back Again... No Matter What tour.

"It was a raunched-up show for the grown-up Boyzone, with half-naked dancers gyrating along to the hits."

When Boyzone decided to reform late last year, they were told by their management they would have to lose weight.

Keating said: "We're all on diets and we've been training in the gym every day. I'm probably the fittest now that I've ever been. I think we all look better now than before.

"We had all put on a few pounds and the directors took one look at us and said, 'For starters you're all going to have to lose some weight or get in shape or we're going to have to pull all the dance routines."

Treading the boards: The group performed a high-energy routine on treadmills

Heart-throb: Stephen Gately flexes his muscles on stage

When the group first started out in 1993, all five were seen as young, free and single.

Fifteen years later, four of the five are married and gay bandmember Gately entered into a civil partnership with Andrew Cowles in 2006.

Keating has three kids with wife Yvonne, Duffy has two with wife Lisa, Lynch's second wife Sheena is pregnant with their first child and Graham has two children, one with wife Karen and another from a previous relationship.

Boxing clever: Boyzone members Keith Duffy and Shane Lynch work up a sweat

Boyzone are just the latest in a string of 1980s and 1990s pop act to reunite in recent year.

Take That's comeback has been a huge success, but the Spice Girls embarked on half of their world tour before cancelling the remainder of the dates, leaving many fans disappointed.

However, All Saints parted ways with their record company last year after just one single.

Graham tells this week's Heat magazine: "I do think Take That getting back together was a catalyst for us to do the same.

A couple of us went to see their first comeback show, and I remember calling Shane straight away. I thought, 'We've gotta try and so something now.'

"If ever the timing was right to start something, it was then and Shane agreed. Then I was on to Ronan - he'd seen it as well - and the other boys were interested too. Slowly over a two-year period, it came together."

Keating admits he was the only holding up the reunion when the band first discussed it several years ago, because he was enjoying a successful solo career.

He said: "The break was only supposed to be 12 months. A break led to a break up and I was the reason that the band didn't get back together.

"Things were going really well for me and I wasn't going to drop that. It created some animosity between some of us."

As they were: The group at the height of their fame in the 1990s