Shortly after Christmas, it came to my attention that I’d become fat.

It wasn’t an instantaneous realisation. There had been signs. I was only looking at myself front-on in the mirror to maintain the illusion I was still trim. The waist size in my pants had crept up. And I’d avoid glancing sideways at shop windows as I passed.

The power of wilful ignorance did the rest.

But when the pudgy bits started seeping out the sides; when I tried sucking in my paunch and nothing shifted, I realised, finally, that something had to be done.

Cheese, mainly, was to blame. And an appetite that had not diminished since I was a rangy 19-year-old with a white-hot metabolism built for burning carbs. I was that guy spinning the lazy susan at the end of a Chinese banquet, sopping up the remaining sauce with the remnant rice. Then licking the bowl.

In my latter, fatter, years, I’ve also been the guy on the couch in front of the TV shovelling French brie into my mouth at the rate of about $50 a week.

My brand was all appetite, no avoirdupois. Now the love handles were getting big enough to operate a barn door. I’d become stout. Beefy, even. Not noticing wasn’t cutting it any longer.

Vanity was finally demanding its say in the age-old battle against gluttony.

About a year ago, my brother and his wife lost bucketloads of weight. So at a Christmas get-together, we consulted the oracles. Their tip was to follow the late Dr Michael Mosley’s Fast 800 weight-loss program, as they had done. For a maximum of 12 weeks, they said, you follow a very strict plan laid out, recipe by recipe, for three meals a day. The weight will fall off, they said.

The trick with this diet is that, between them, those three meals deliver only about 800 calories (3350 kilojoules) a day – half of what the body would normally consume. It sounded extreme. Monastic, even.

My wife and I looked at each other, chins jiggling in agreement.

“We’re in,” we said.

Spoiler alert: in 10 weeks, I lost more than 16 kilograms and she about 12. I went from obese on the BMI to “healthy” for the first time in years. I feel great. Alert. Energetic. Limber, even. Also hungry, pretty much all the time.

But now, when I ride my bike, I fly up hills because I’m no longer dragging the equivalent of a half bag of cement in my saddlebags. At the gym, I’m attending to my core again - because I have one.

So, how was the journey? Well, at times, tough.

Here’s how it works. You buy the app for $125 and start fasting on a Monday. The program lasts up to 12 weeks, unless you reach your target weight sooner.

The app generates a weekly shopping list. You cook the recipes. You eat them. Then you wonder what’s for the main course.

“Guardrails,” my wife said. “Don’t give me choice. Give me rules.”

“Enjoy the flagellation,” said my brother, who might have been a penitent in a previous life.

During one particularly deep afternoon slump, I wondered how long I had to go. I did the calculation. It was day 2. There were 82 left. 

At the start, my legs twitched at night. The internet told me it was cortisol, the stress hormone coursing through my system. I reckon it was my fat, sensing danger, rising up in self-defence.

I also peed a lot. Perhaps it was the extra water recommended because I was getting less liquid through my food. My wife, who actually read the extensive educational material provided in the app, and followed the exercise program, told me the fat was being excreted through my urine. It was a comforting thought when I got up during the night, yet again, to leak.

And boy, was I hungry. The first night I got home from the office to the smell of dinner cooking – chicken and bok choi. I hovered over the pan, “helping”. Then I paced. Then loitered for a while. After that, I hopped from foot to foot as the garnish went on. Finally, I was allowed at it.

What saves this diet is the recipes. Obsessed as Mosley was by the Mediterranean (an obsession that arguably killed him), the Fast 800 is full of tasty, nutritious meals that, despite their paucity, are simple and strangely satisfying.

It should be called the Spinach 800, though. That would be more accurate.

Not being my normal mode, self-denial turned out to be tricky. During one particularly deep afternoon slump, I wondered how long I had to go. I did the calculation. It was day 2. There were 82 left.

Mid-afternoon, I might text my wife. “Peckish,” I’d say. “Me too,” she’d reply.

Some days, I experienced an emotion I can only describe as grief as I put the last forkful of dinner in my mouth.

The hardest times, though, were after dinner. In those hours, a small but insistent voice would say one simple but compelling word: cheese.

I made herbal tea instead. My whole family swears by tea, but I’m infamous for disparaging it as a “gratuitous hot drink”. Now I slug it down. It tastes just as horrible, but it’s something to put in my face – and an aid to extra pee.

I did, though, genuinely look forward to the meals. Yoghurt and berries for breakfast never tasted so good. Who knew you could turn zucchinis into a low-carb substitute for noodles using just a special kind of peeler-grater? Or that they taste sensational with prawns and lemon zest?

Mozzarella and parmesan (diet cheeses, apparently) got a thorough workout.

Spinach (did I mention that?), paprika and capsicum were on high rotation. Spinach featured in everything from breakfast smoothies and omelettes, as a bulking agent in lunchtime salads, and as the main feature, with paneer, at dinner.

There were precious few carbs. And I mean precious. We high-fived each other one morning when a few meagre grams of rolled oats appeared on the breakfast menu.

What else delighted? Mushroom stroganoff; mozzarella chicken; pork balls in soup; pizza base made of mashed cauliflower. I discovered the joys of quark, cottage cheese and berries – and, importantly, that being hungry would not, in fact, kill me. At least, not immediately.

I learned to eat more slowly. Gobbling food meant it was gone too soon.

Socially, it was a mixed bag. At the start, all people noticed was the not drinking and the canape refusal at parties. I was acutely aware of bad breath brought on by ketosis.

Towards the end of the program, people noticed the weight loss. That was nice. (Except for the colleague who, worried, asked friends if I had cancer.) I hate that some people might think we were on Ozempic.

After reaching my target weight, carbs could make a slow comeback, and it turns out a little goes a long way. After eating a couple of slices of toast and a rice cracker or two, my morning bike ride felt like someone was propelling me. It felt like putting rocket fuel in the tank of an old Camry.

I do think, though, that I’ve become slightly carb-phobic. At a function recently, a bowl of fluffy white bread rolls looked a bit like hand grenades.

But the self-satisfaction is strong.

Because she loves me, my wife didn’t tell me I’d been walking around looking eight months pregnant. Well, to be accurate, she waited until after I’d pissed out my lard baby to tell me that. It’s one of the reasons I love her.

Vanity restored, my next project is a six-pack – and a reintroduction to my beloved cheese vendor without courting corpulence.