Showing how restrateurs lose weight...

There comes a point in every young man's life when he must look in the mirror and think to himself: hmm, pig or twig? Hero or zero? Especially if he works in a restaurant and is surrounded by freshly sourced, beautifully cooked food every day, with no threat of washing-up to do afterwards.

The day of reckoning came recently to restaurateur brothers Sam and Eddie Hart, who found enormous success in London when they opened their Spanish restaurant, Fino, in 2003, followed by the tapas bar Barrafina earlier this year. Influenced by their Majorcan mother and extensive travels, the brothers are passionate about all things Iberian, and the customers who flock to both restaurants have happily matched their passion for sherries, fluffy potato croquetas, richly flavoured Spanish hams grilled with sweet, yellow fat, plus gambas al ajillo, smoky morcilla, crisp pork belly and individual tortillas made to order three different ways. Yum yum, yes please.

Of course, there are lots of less calorific items on both restaurant menus, but when you cut into their classic tortilla, the yolky insides weep over stacks of soft potato in an utterly distracting way. The Fino chips come slathered in a chillied-up brava sauce speckled with thyme. It's all so delicious, and the Hart brothers thought so, too.

"But the problem was, when Sam and I opened Fino, we sat down and had lunch and dinner there every day. We ate the menu. We had to; it was all about quality control. It was the same with Barrafina,'' says Eddie.

So with the triumphant expansion of the brothers' nascent empire came growth of another sort - and this time the development was rather more unwanted. To put it bluntly, Sam and Eddie were getting fat. With their penchant for smartly tailored suits and neat haircuts, the Eton-educated brothers were beginning to look like the Tweedledum and Tweedledee of the restaurant industry. Something drastic had to be done.

"All of a sudden, you look at yourself and think, oh dear, I'd better do something about this,'' says Eddie. "I kept noticing that my trousers didn't fit any more and thought, hmm that's strange.''

"And Eddie has always been thinner than me,'' says Sam, who is 32 and married with two children. "At 13, I was too heavy to play for the school at rugby sevens. I have got a bigger frame, but I am greedier of course.''

Eddie, who is two years younger and has a girlfriend, says, perhaps rather sadly: "We have another brother who works in the City. He's the real sportbilly.''

Over a family dinner at St John restaurant in London, as they tucked into a last supper of bone marrow and suet pudding, the brothers decided to get fit. In fact, they decided that the only way they could stop the rot was to start triathlon training. "Plenty of drink had been taken. We were at the brandy stage at the point when we agreed to do it,'' says Eddie, "but the next morning, we decided to go ahead anyway.''

It is not surprising. Triathlon, which is the fastest-growing sport in Britain, is becoming an increasingly popular means of getting fit, with about 500 events taking place annually up and down the country. Ten thousand people participated in the 2007 London Triathlon at the beginning of this month - half of whom were competing for the first time.

The sport involves a continuous race comprised of a swim, followed by a cycle and then a run. Part of a triathlon's popularity is that the training is more varied and interesting because of the multi-discipline demands. In the triathlon itself, competitors race against the clock, which starts as they begin the swim and stops when they cross the finishing line after the run. Triathlons can be various distances: a proper Olympic triathlon involves a 1,500m swim, a 40km bike ride and a 10km run. The Hart brothers feared this might be too ambitious for a couple of out-of-shape restaurateurs, so opted instead for a three-quarter triathlon, which involved an 800m swim, a 30km bike ride and a 7.5km run. Still not exactly a walk in the park. They began training on March 17 and took part in their triathlon on July 22. The results were spectacular.

In the space of only 67 days, the brothers lost 21 kilos between them, look as sleek as seals, and say that they both feel much better, physically and mentally, than before they started.

How did they do it? They joined a gym and started cycling to work. The only professional help they received was a few swimming lessons each. "The swimming was the scariest bit,'' says Sam, "but it's amazing how you improve after only a few coaching lessons.''

Eddie's fitness regime also involved making the Fino and Barrafina chefs promise not to give him his favourite foods.

"I have a concrete rule with the chefs. No croquetas, no tortilla, no Fino chips with brava sauce and definitely no pork belly,'' he says.

"I try to eat just fish and salad,'' says Sam. "I'm very strict on Mondays, less so as the weekend approaches. Sometimes I have a glass of wine on a Friday. We have both realised that you have to have a regime. If you want to be in this business for the long haul, you've got to make a decision to be disciplined. Despite the popular myth, there aren't that many jolly, fat restaurateurs. And almost no overweight chefs.''

Certainly, many older and more experienced chefs and food professionals have managed to work out a fitness regime that counters the calories they have to consume in their line of work. It normally involves running for about 100 miles before breakfast and jogging on the spot for hours every time they even think about a nice slice of chocolate cake, or some more of that rabbit wrapped in pancetta with a side of gratin dauphinoise.

Gordon Ramsay, Michel Roux Jnr from Le Gavroche and Phil Howard from The Square are all dedicated marathon runners. Heston Blumenthal is a kick-boxing champion. Tom Aiken plays polo and cycles everywhere. Nigel Slater swims every day. They are all practically professional athletes, and in addition to this they watch what they eat.

Gordon Ramsay does not fill his boots with three-star Michelin cuisine on a daily basis. Anything but. He will regularly have only a fresh fruit smoothie for breakfast ("but a bucket of it'') and something simple, such as cheese on toast, for lunch. Michel Roux Jnr may cook sublime dishes such as lobster mousse with caviar and champagne butter sauce for his Gavroche customers, but at home he eats poached chicken, lamb with couscous and grilled mackerel.

He wrote a book about what he eats when he trains for marathons, and how his desire for red meat, cheese, butter and even wine diminished the fitter he became. All these men have discovered that there is more than one way to concentrate on good food, and that if you want to survive and thrive in the industry, it is the best way forward.

Sam and Eddie Hart gained early experience of the restaurant industry - their father is the owner of the Michelin-starred Hambleton Hall Hotel - but there are lots of things to keep learning as they go along.

The newly lean brothers feel that keeping fit is now an important part of their lives and look forward to more training challenges in the future. They are considering taking part in a champagne-sponsored bicycle race, which involves a 300km cycle from London to Reims. That sounds demanding.

"Yes, but you get to collapse inside Château Bollinger at the end,'' says Eddie. That sounds as good a way as any to live a life.

* Fino, 33 Charlotte Street, London W1; 020 7813 8010. Barrafina, 54 Frith Street, W1; 020 7813 8016. See our reviews of their restaurants elsewhere on Are You Ready To Order

The British Triathlon Federation: www.britishtriathlon.org

Lean cuisine: Eddie and Sam at Fino, above, and how they looked before their fitness campaign, left. Below, training for the triathlon. In only 67 days, the brothers lost 21 kilos between them