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GQ's most unfit staff tested Britain's latest gyms and exercise fads to see which one burned the most fat, built the most muscle and hurt the least. Don't make your new year fitness resolution until you've read this…

Rebel by Matt Jones (33, 6ft 3in)

Everyone at 1Rebel is beautiful. The people who use the gym. The people who work at the gym. Even the staff at the smoothie bar - this is a London gym, so obviously there's a smoothie bar - would give me a run for my money on Hot or Not. This is relevant for one reason. Motivation. Something you need by the bucket to get through a Reshape class.

Essentially, it's high intensity interval training (sprint on a treadmill for a bit, lift up some weights, squat, do a few thousand press-ups, back on the treadmill, repeat for 45 minutes). But it's so much worse than that. The sweaty and pitiful are singled out and told to "add on" (run faster) or "push bigger" (lift a heavier thing up) by an instructor who looks like he's escaped from the front cover of Men's Health.

Then there are the mirrors.  They're everywhere, so when Mr Men's Healthshouts "Ask yourself WHY ARE YOU HERE? C'mon Rebels, push!" you have no energy spare to cringe at being called a "Rebel", and through eyes of chipped granite you can see your puce, sodden reflection staring back at you, answering his question.

At this point, you will look at your treadmill neighbour to see if they're also sweating through their knees (I phenomena I discovered at 1Rebel). They won't be. They will be beautiful, dry as a bone and taking a selfie, answering an email or fixing their perfect spun gold hair. 

You can deal with this in one of two ways. Go home and have a pizza, or knuckle down. Much to my surprise, I managed the latter. I quit drinking, swapped my breakfast for a Protein Works shake, ate two meals a day supplied by Yolo food(a new company that delivers healthy, balanced meals to you every day) and got myself some proper Saucony running shoes chosen after a gait analysis (you absolutely need these for 1Rebel or your knees will grind to powder).

Exploiting my position, I asked Olympic nutritionist, GQ's Fitness Correspondent and impossibly swole man, Ross Edgley, when best to go. He suggested engineering break days and maximizing recovery times to protect my imune system (work out too much and you get ill, apparently). As such, my workouts took place on Monday morning, Tuesday morning, Wednesday evening, Friday lunchtime and Saturday evening. 

The results were, frankly, astonishing. The green shoots of a six-pack emerged and my fitness levels shot up. OK, so I was a long way off 1Rebel-beautiful after three weeks but I'm proud to announce that I can run for slightly less than an hour without sweating through my knees. 

The results (before and after 1Rebel)

Body fat percentage: 20.5%/16.4% (-4.1 percentage points)
Body mass index figure 25.4 (Overweight)/24.8 (Healthy Weight)
Weight 93.9kg/90.8kg (-3.1kg)
Hips measurement 91cm/89.5cm (-1.5cm)
Arm measurement 38.6cm/39cm (+0.4cm)
Thigh measurement 61.3cm/61.5cm (+0.2cm)
Belly measurement 95cm/92cm (-3cm)

We trained at 1Rebel St Mary Axe. Get Saucony shoes via Saucony and Yolo Food via Yolo Food Company 

Barry's Boot Camp by Conrad Quilty-Harper (28, 6ft) 

Barry's Boot Camp is the best gym I've ever been to. Admittedly, it's the only gym I've ever been to, but that's beside the point. For someone like me who's sustained a very unhealthy disdain for gyms and gym goers ever since my last school PE lesson (one of the happiest days of my life), this is quite a feat. Everything at Barry's is taken care of: you only have to turn up wearing appropriate clothes and shoes. Everything from the changing rooms, which have built-in number pad locks, to the showers, which dispense free Malin + Goetz shampoo, is inclusive and high quality.  

The do-everything attitude extends to the trainers who are experts in the various different training techniques and the psychology of getting lard arses like me to enjoy having my body destroyed and built up again. Yes, I enjoyed Barry's Boot Camp. Despite learning on my second class that it was possible to retch from exercise. Despite developing tendonitis in my right ankle which meant I couldn't walk properly for three weeks (get your gait analysed before you start and buy proper running shoes). And despite creating a sea of sweat on the floor, grunting and screaming in agony at every single class. This is all possible thanks to the perfectly balanced carrot and stick approach of my trainers Alex, Jay and Taylor. They know how to safely push you to and beyond your physical limits.

The first week at Barry's Boot Camp, after never exercising more than the occasional cycle commute, is like getting hit by a bus. And you might even prefer that. You'll feel dizzy getting off the treadmill. You'll physically and impulsively scream in agony. You'll cry climbing stairs and sitting on toilets. But after just three weeks you'll also benefit from a rush of endorphins every afternoon, you'll discover what having muscles actually feels like, and you'll get a sustained surge of testosterone which translates into an appetite for food, sleep, sex, and life in general. I've learned to love exercise, and it's all thanks to Barry's Boot Camp. 

The results (before and after Barry's Boot Camp)

Body fat percentage 21%/18.7% (-2.3 percentage points)
Body mass index figure 25.8 (Overweight)/25.1 (Overweight) (-0.7)
Weight: 86.4kg/83.9kg (-2.5kg)
Hips measurement 93cm/93cm (no change)
Arm measurement 31cm/32cm (+1cm)
Thigh measurement 61cm/62cm (+1cm)
Belly measurement 96cm/93cm (-3cm)

We trained at Barry's Bootcamp East London 

Crossfit by Nick Carvell (29, 5ft 11in)

I've had a few friends being inducted into the cult of Crossfit. However, past the seemingly obligatory shirtless selfies I saw these friends post on Instagram, I really had no idea what the exercise regime entailed - and that's exactly why I wanted to do it. Turns out it's military circuit training with a mix of bodyweight exercises (pull-ups, burpees) and Olympic weightlifting - in short, not really something for the feint hearted. Thankfully, the masters at Crossfit Blackfriars - Mateo, Matt and Brian - are there to guide you through. 

While it's hard work (fair warning: you'll probably vomit), what you learn quickly is that Crossfit is the perfect halfway house between personal training and group work - you're trying to beat your own personal bests on circuits, but supervised at all times by an expert (much needed if, like me, you've lifted little more than a mug before). You'll also learn that Crossfit acolytes are crazy for official merch - a few classmates thought I was an old-timer at my first session because of my Reebok Nano 5.0 trainers and matching branded kit. Sadly, my shaky moves dashed that impression immediately.

It was damn tough for a fitness newbie, but beyond the results (that I was very pleased with), what I really valued were the skills I picked up - especially how to lift properly - and the camaraderie of the group. If you're the kind of guy really wants to change, but still needs egging on to achieve your goals, then this is the regime for you. 

The results (before and after Crossfit)

Body fat percentage: 23%/21.2% (-0.8 percentage points)
Body mass index figure: 24.3 (Healthy Weight)/25.8 (Overweight) (+1.5)
Weight: 79kg/82kg (+3kg)
Hips measurement: 108cm/100cm (-8cm)
Arm measurement: 36cm/32.5cm (-3.5cm)
Thigh measurement: 68cm/63.5cm (-4.5cm)
Belly measurement: 103cm/91.5cm (-11.5cm) 

We trained at Crossfit Blackfriars. Get crossfit kit via Reebok  

The Orange Theory by John Hitchcox (32, 5ft 10)

With a heart rate monitor strapped to your chest, each hour session consists of a high intensity mix of running, rowing and floor work (arm, leg and ab exercises) while you gaze upon televisions that display the percentage of your maximum heart rate you're currently working at, your BPM and the calories you've burned so far. It's also colour-coded based on the zone you're currently sitting (read: struggling) in.

The grey and blue zones are barely worth mentioning, it's the green zone and above you need to be aiming for. Green means you're in the fat burning zone and you'll spend most of your session here. Once you reach around 84 per cent of your maximum heart rate you hit the orange zone - and this is where the good stuff happens. Not only are you burning through your fat you'll also continue to burn calories for up to 36 hours after exercising: the afterburn. Essentially, bonus exercise without the effort. Win. Above orange is the red zone, which is where professional athletes tread (or sprint) and is for conditioning for actual sport. The great claim of Orangetheory is that, as long as you spend 12-20 minutes in the orange zone and above, you will burn up to 1,000 calories per session.

In the UK, the Orangtheory franchise is run through David Lloyd and it was the Islington studio I visited. Guiding you through the ordeal is a trainer who sets the plan for each session, which varies day-to-day. The trainers are excellent and tread the perfect line between being enthusiastic and encouraging without stepping over into being pushy and army-like. It also turns out that each class (thankfully) consists of normal human beings of varying fitness levels and body shapes. Not as scary as first thought.

I'm not going to lie though, the first week was a struggle. Luckily you can choose the right exercise for your fitness level and I spent most of it in the lower band of the class, selecting to be a "power walker" during the running machine section of each class, occasionally opting for "jogger" but never venturing into "runner" territory. A sit up was a struggle and I couldn't give you ten if you paid me. Gradually, through week two, I was able to pick up the pace and I was actually enjoying it. By week three I was running and/or rowing around 6km each day at a decent speed and was able to actually do press ups. Kind of. 

This amount of running holds its risks for the unfit. During one session I started to feel pain in my knee, but rather than push me on toward injury the trainer saw something wasn't quite right (before I did) and suggested an alternate exercise thus saving me from abusing myself further and the embarrassment of giving up after seven classes.

You also have to consider the amount of calories you're actually burning. Depending on your starting position, using up to 1,000 per day for three weeks without adjusting your diet could end in a Christian Bale style transformation. Not Batman, the other one. I'm talking Machinist potential. Alternatively, binging on the wrong food could mean not having the energy to even complete a session. To compensate I sought professional help in the form of Fresh Food Fitness. They designed a four-meals-a-day diet that had the right fats, carbs and protein to see me through, while aiding muscle gain and loss of body fat. Each day's food is prepared fresh and delivered to your door before 6am, saving you the hassle and meaning it actually tastes of food. Real food.

As for the results, there's no doubt Orangetheory works. I may not have gained inches on my bicep (although I'm certainly more toned) but it's impossible not to lose body fat, increase stamina and feel incredibly smug after three weeks. No six pack, but I can certainly feel abs beneath the surface of what was once some sort of forgotten void where muscles dared not venture. In fact, I lost an inch and a half from my belly, an inch from my waist and can now run for forty minutes without dying. The crazy thing is that I'm still going, which is the best recommendation of all.

The results (before and after Orangetheory)

Body fat percentage: 20.2%/16.5% (-3.7 percentage points)
Body mass index figure: 23.2/23 (-0.2)
Weight: 73.5kg/72.9kg (-0.6kg)
Hips: 86.4cm/83.8cm (-2.6cm)
Arm: 31.7cm/31.7cm (no change)
Thigh: 52.7cm/53.9 (+1.2cm)
Belly: 85cm/81.2cm (-3.8cm)

We trained at Orangetheory through David Lloyd in Islington. Get Fresh Food Fitness via Fresh Food Fitness

Heartcore by Ryan Grimley (23, 6ft 1in)

My first class started at 7am at Heartcore's City studio, so when I arrived I was neither bright eyed nor bushy tailed. To say I felt out of my depth was an understatement. But after learning how the Reformer Pilate beds operate (don't ask) and working out my downward dog from my elbow I was on my way, sticking to a plan of 21 classes and a strict diet that stripped out carbs and alcohol.

I had two classes in my fitness plan, TRX suspension training and Pilates. The first is the calorie killer and involves bodyweight exercises while you're suspended from the ground on rubber bands. Apparently, you'll burn 700 - 1,000 per 55 minute class, but also builds strength, flexibility and balance.

Then there's the Pilates, which is heavily focused on core strength and toning and involves pulling on various ropes and handles and, for me, results in full-body shaking. Nevertheless, the balance of two classes meant my workout was a great attack on the flab.  

A week and a half in, I was 12 classes down, using muscles I didn't even know I had. It was a case of call it quits or suck it up. My Adidas Ultra Boosts were well beat in, I ached everywhere, but a few things kept me from calling it quits. Firstly, the facilities. I rotated between three studios (Fulham, Chelsea and City), all of which had showers, towels, deodorant and three different shampoos (obviously), so there was no excuse to stay in bed.

Then there was the wellbeing. Having never really taken on this much exercise, I discovered that - despite the aches and pains - you actually feel a lot better in your own body. Your mood's better, you sleep properly and your concentration levels go through the roof. 

Then there were the visual results. By the end of the three weeks I had a visiblesix-pack, my arms were bigger and more defined and my man boobs had turned into muscle. The first class might have intimidated me, but once I'd made it to three weeks I was skipping to the gym. 

The results (before and after Heartcore)

Body mass index figure: 24.9 (Healthy weight)/24.1 (Healthy weight) (-0.8)
Body fat percentage: 20%/17% (-3 percentage points)
Weight: 85.7kg/83kg (-2.7kg)
Arm measurement: 35cm/35.5cm (no change)
Chest measurement: 99cm/96.5cm (-2.5cm)
Thigh measurement: 48cm/50cm (+2cm)
Belly measurement: 95.3cm/89.4cm (-5.9cm)

We trained at Heartcore in Fulham, Chelsea and City via Heartcore

Broga by Max Williams (24, 5ft 11in)

My first session of broga was among the most traumatic hours of my life. A stark realisation of my complete inflexibility and ungainliness. Touch my toes? I could barely reach my knees. Downward Facing Dog caused my arms to ache after a matter of seconds. Don't mention the chaturangas (planks with a push-up). I had to keep my knees grounded in order to lift my torso off the ground. 

I left the gym cursing. Yet after half an hour something strange happened. An enormous sense of well-being descended. My limbs felt loose, supple. My joints sang. True, this sensation was later replaced by some rather intense aches but for a moment I glimpsed enlightenment.

That whole first week was a challenge. I was stretching muscles that I'd literally never stretched before, forcing my body into contortions that seemed specifically designed to inflict maximum amount of pain. Broga is not something you immediately pick-up. A good trainer, at least at the start, isn't important but mandatory. You need support when attempting your first handstand since the age of ten. 

But my God, you feel those benefits. After a fortnight I had shoulder muscles for the first time in my life. My whole upper body looked stronger, better built. And the legs! 15 days of stretches, strains and squats really moulded those pins into shape. Chaturangas? I'll do them on my head. (And basically had to.)

However the gain isn't limited to physique. By the end of the course I was looser and more flexible than ever before. My concentration improved. My resolve was stronger. I felt calmer, more relaxed. The breathing control and focus trained by broga benefits many aspects of life. It won't dramatically build muscle or shed weight in the manner of extreme boot camps or rebel insurgencies but that isn't the point. Broga is a sustainable, and surprisingly enjoyable, workout for both mind and body. Go investigate. 

The results before and after Broga

Body mass index: 26 (healthy weight)/25 (healthy weight) (-1)
Body fat percentage 24%/21% (-3 percentage points)
Weight: 85kg/82kg (-3kg)  
Waist measurement: 95cm/94cm (-1 cm)
Arm measurement: 32cm/34cm (+2cm)
Thigh measurement 59cm/63cm (+4cm)
Belly measurement 98cm/96cm (-2cm)