One hundred and three, one hundred and four,” I counted the number of steps in my head; I was too out of breath to say them out loud. My legs were wobbly, my thigh muscles pumping as I forced myself up the steep hill.

To distract from the burn I began humming the theme tune to Rocky, imagining myself competing against the grey tracksuit-clad boxer Balboa as he sprinted up the steps of the East entrance of the Philadelphia Museum of Art in the hit movie.

Only I wasn’t getting ready to compete in the ring by pounding the streets of a cold, inner city. The only thing I was fighting right now was the flab as I tackled my first day at the luxury No1 Boot Camp in the beautiful surroundings of Ibiza.

Normally known for its celebrity tourists – Mick Jagger, Robbie Williams, P Diddy and Kate Moss are all regulars – or as the clubbing capital of the world, I was here to see a different side of the Balearic island.

Based in the quiet, rural idyll of the north east, a mere 30-minute drive from Ibiza Town, the fitness retreat might as well have been a million kilometres away. Instead of a huge conglomerate hotel I was staying in a luxurious villa with jacuzzi, outside swimming pool and resident personal trainer Ricky Parcell and nutritionist Kate Whale; there were no clubs around, only the nearby Atzara boutique hotel and spa, and the other guests weren’t here to party. They had come to lose weight and get fit. Like me.

A year in Dubai and my weekends of brunch, beach and the beautiful life had seen me gain 18kg. My hard-earned ripped torso had disappeared under a paunch and my once-chiselled jawline now boasted an extra chin. I’d tried hitting the treadmill and the cross-trainer but temptation was always only a five-star hotel and restaurant away, so I decided to use my annual holiday to ship out and get myself in shape.

So here I was on my first morning, after being woken by blaring music at 6.15am, with sweat running in rivers down my back, sticking my hair to my head in the 36C heat, while marching military-style after Ricky and the 12 other boot camp guests (11 women, and an ultra-fit action-man type). We’d already done a 20-minute ‘box-a-run’ through the countryside, stopping along the way for military-style exercises on the spot: boxing, lunges, jumps, sprints, with only a quick stop for breakfast – four tablespoons of muesli with milk – before heading to the hills.

Now, reaching the top, panting and grateful the climb was finally over, I was ready for the descent. But the only way from here was up – Ricky led us up a mountain, where the path became so narrow we could only put one foot in front of the other, and I daren’t stumble because of the sheer drop down to the sea 200 metres below.

Up, up and up we went, clambering over rocks, through pine trees, past ancient stone ovens in the middle of nowhere, and past Can Vali, where French footballer Zinedine Zidane was holidaying. Luckily, I’d been told to bring hiking boots as this was no morning stroll, but a climb towards the sapphire-blue sky, ending with us perched on top of the rocks above the azure sea.

To pile on the pressure, when there was space for it, those at the front were told to loop back round and encourage the stragglers – me included – to move it even faster.

Three hours later, scratched by the trees and every muscle aching from the arduous climb, we arrived back at the foot of the mountain. “Take a dip in the surf,” Ricky, an ex-marine, ordered and I ran into the Mediterranean Sea, the cold salty waves soothing my battered body.

It was mid-morning and I was ready to go to bed, I didn’t have any energy left. Luckily after a lunch of tomato soup, which was absolutely delicious but sadly a tiny portion, we were allowed a two-hour break.

Some of the guests went to read books and sunbathe by the pool. I hit the sack and went straight to sleep until 2.30pm, when it was time to start exercising all over again.

“I know why they call it a boot camp,” I thought, holding on to mine to do 50 sit-ups. We were outside the villa, where the trainers had set up a circuit for us to pound a boxing bag, do bleep tests, where we had to race against the clock and do pull-ups, push-ups – every kind of ups – and the real army move: burpees.

Burpees are, for the uninitiated as I was, the hardest exercise ever, even by soldiers’ standards, consisting of squatting down, doing a push-up and then jumping up as high as possible. It hurts, and we had to do 45 minutes of them per day.

By the end of the afternoon, I was in agony. My leg muscles were like lead and I feared I was going to collapse. “Next year I’m going to Las Vegas,” I promised myself, hobbling indoors, every muscle and sinew on fire. Luckily, I’d booked a massage for every night. I’d imagined this boot camp would hurt and I was right.

After a shower, I gingerly climbed a few more steps to the rooftop terrace and lay, watching the sun turn orange then pink as it sank over the hills, soothed by a cool breeze as one half of the Dutch couple, Abi and Bunky, offering facials and massages, kneaded my tender muscles. To say it was the best hour of my life right then was an understatement.

I had never worked so hard, or been so exhausted, and this was the only way I was going to be able to get up the next morning and move without wincing.

Massage over and it was time for dinner. We ate together, devouring our noodles with vegetables washed down with glasses of water. We weren’t allowed salt, sugar, sweetener or dessert, but no one complained. But that was because we were all too tired to talk.

That was why we were here though – to improve our fitness and our bodies, so no one sneaked out to explore the island or the nearest restaurant. I can’t say it was all because we were so highly motivated. We didn’t have the energy to go anywhere except to bed early as we’d be up early again the next morning for another packed day of exercises.

My first day, I soon learnt, was pretty indicative of the rest: hikes, sometimes with a guide – islander Toby Clarke – to point out the plants, wildlife and picturesque coves, nooks and crannies (every view was breathtaking but then again a large amount of the White Isle is Unesco World heritage sites) and military-style exercises. It could have been a blur of classes but the other guests on the course – who were all much fitter than me and very friendly – and the beautiful scenery made it enjoyable.

And it wasn’t all about fartlek training – it means ‘speed play’ in Swedish and mixes continuous training with interval training – and Tabata training – high intensity interval training – both of which hurt and reduce girls (and sometimes boys) to tears. We had fun too. One day we had relay races in the pool, along with volleyball, where we laughed and could have all been old friends at a villa splashing about.

We had to compete with each other but the real competition was with ourselves – pushing our bodies to be faster, walk or run further, and perform each exercise better. It was a mental as well as a physical battle and I kept myself going with one thought: paella.

Overlooking the sea, just a short stroll away from the villa, was a restaurant with smells of Spanish fare that tempted us most nights as it wafted up on the breeze. “Let’s eat there on our last night,” I told the others. They all agreed – after all, what better way to celebrate losing lots of weight than with a slap-up meal? So when I was doing planks, squats and boxing moves I imagined taking my first spoonful of paella – it inspired me to work harder so I could have seconds.

As the days rolled on, we bonded over talk about repetitions, ripped abs (some of them now had them, I could only dream) and restaurants. But the pain subsided, and I discovered that I quite liked working out. Even the fartlek training. And all of us were looking better, feeling fitter and losing inches as well as kilos. I only lost 1kg*, but Ricky told me I’d lost eight inches all over, and had actually increased my biceps and thighs.

“Muscle weighs more than fat, you’ll shed lots more weight next week,” he said. I went to change – and grinned. The jeans I’d worn on the way over had been tight with my stomach bulging over the waistband. Now they were loose.

Delighted, we all went to change for our last supper. We all looked so different dressed up for a night out and hit the road to the beachside restaurant with a spring in our superfit steps. “Delicious,” I said, minutes later tucking into a plate of paella. “Even more delicious,” I said after that, devouring another portion. Right then I didn’t care how many calories or fat my dinner contained, I just wanted to enjoy my evening with my new boot camp buddies.

Climbing the steps to the plane back to the UAE, I felt so elated by the past week’s achievements I was tempted to sprint up them Rocky-style, and raise my hands over my head at the top in triumph. It had been a hard week’s ‘holiday’, but it was definitely worth it.

*Oliver lost 1kg at the boot camp and has lost a further 13kg since.