It's no accident that Gordon Ramsay's latest cookbook, Healthy Appetite, serialised in The Times from next Saturday, kicks off with porridge. It's a reminder of his tough Glaswegian roots, and his father's view that only poofs add sugar rather than salt.

Ramsay learnt about healthy living the hard way - from his father, who died of a heart attack at 53; while his mother, who cooked healthily but smoked heavily, had a quadruple bypass two years ago. “I get so frustrated today when everyone blames children for eating badly,” he says. “It's not kids; it's parents. I think they should be fined for letting their children get out of control because it's our discipline, our standards that they follow.”

Intriguingly, Ramsay, 41, who is as famous for bad language as for his nine Michelin stars, doesn't emphasise this point by swearing. Indeed, he uses only a smattering of F-words in our two-hour conversation, which ranges from his battle with his weight and his old-fashioned views on parenting, to addiction - his brother's to heroin and his own to perfection - and the religious faith, which has seen him through his struggle with infertility and the premature birth of his twins, now aged 8.

Ramsay's language gets a tad fruity only when he has a pop at Delia Smith. One look at How to Cheat at Cooking was enough for him: “I was absolutely horrified. I'm embarrassed for her. I don't expect cooking from tins and frozen food from one of the nation's most precious individuals, who gave so much hope and security to domestic cooks. I'm bitterly disappointed, but more importantly, concerned that, as a nation we're going backwards and people will continue being lazy.”

He's not the martinet of his TV shows

It could be that Ramsay's language is tempered because we are talking in his front room in Wandsworth, South London, with giant furcovered beanbags and a cosy domestic hum in the background. Words fly out of his mouth in a breathtaking stream of consciousness, but there is no hint of the martinet who makes mincemeat of provincial chefs in the Channel 4 show Ramsay's Kitchen Nightmares.

When Ramsay's three daughters - Megan, 9, Holly, 8, and Matilda, 6 - arrive home from school, his face gets even squidgier than normal. Like a fond Victorian father he summons his brood in to hear their news before dismissing them to the care of his serene wife Tana, who happily gave up nursery teaching to look after them. The couple set great store by good manners, and it shows, even if Jack, Holly's twin, has started fining his dad when he isn't there to watch him play football.

One can only conclude that Ramsay is a bit of a Jekyll and Hyde. Or could it be that one of his performances - the irascible monster on TV or the charmer in our interview - is an act? If anything, it's surely the former: people who work with him testify to his kindness and consideration, and he inspires enduring loyalty. Of course, this ability to inspire loyalty is a plus for him: talented protégés, such as Angela Hartnett, who is opening Murano, an Italian-style restaurant in London this summer, run restaurants for him, under his brand, instead of setting up on their own as competititors. You might say that personal loyalty keeps the constantly expanding Ramsay empire thriving. He has just opened restaurants in Prague, Versailles and Heathrow Terminal 5, to be followed later this year by Los Angeles and Amsterdam, and he has added three pubs to his seven London establishments.

When it comes to healthy food at home, Ramsay admits to disguising veg and bribing his children. He agonises about seasoning, which is one of his obsessions. “I've got to protect the children's palates; I can't expose them to the amount of salt which with my palate I find perfection.” He adds: “At home we keep food exciting but plain. I had a humble upbringing and we didn't have a choice about food. What fascinates me today is that some of the parents that I meet are tailor-making dishes for each child in the family, providing an à la carte menu. They are being held to ransom.”

Ramsay's own childhood, with his younger brother, two sisters, heavy-drinking father and long-suffering mother, was spent moving from council estate to council estate in England after the family left Glasgow when he was still in a pushchair. They finally settled in Stratford-upon-Avon, where his mother cooked in the tea rooms and he grew up on steak and kidney pud and fish and chips. So he makes huge efforts to make sure that his own children are not “little snobs” about food or anything else, even if that means allowing his mum to take them to Butlins every August when he and Tana would really rather go to France. At weekends, the dishwasher is unplugged so the children get used to washing up.

Trying to keep life really normal

“We fight the lifestyle we've worked our arses off to create, and we do everything we can to keep life really normal,” he says. “When I watch Jack playing football on Saturdays I am horrified by the parents who are screaming at the coach saying they're not happy with the training and their son should be captain. The last argument Tana and I had was when Megan didn't get into the netball team. I said it was good news because she needs to know what it feels like to be rejected because it will make her more determined. Now she's in the B team.”

At the same time, Ramsay relishes the lifestyle that his estimated £60 million fortune brings. Last year he flew his mother to Mykonos in a private jet for a surprise 60th birthday. She is the remaining link with his younger brother Ronnie, a former heroin addict who recently left rehab in the US. Ramsay supported him financially for years, but stopped when Ronnie, 40, was arrested in Bali a year ago.

“I had to turn my back on him, otherwise I would have been bailing him out knowing that I was part of what got him in there. Of course, I'm dying to talk to him, but I can't because I could trigger another relapse; I'm scared to get close because I would end up spoiling things again. A distance needs to be created before we can resurrect a relationship. But it hurts me and I know deep down inside it must hurt him.”

Ronnie's heroin addiction is mirrored in Ramsay's much happier addiction to perfection - which he has never seen as a problem - and his relentless need to keep raising the bar. He is one of only three chefs in the UK with a three Michelin-star restaurant, but wants to match that in New York (where he has already got two within ten months of opening) and Paris, where his new restaurant opened last month.

He traces his phenomenal drive back to the failure of his footballing career with Glasgow Rangers at 18 because of injuries. He fell into catering by sheer accident; it was his mother's idea. “Getting into food was a way of hiding the hurt and the insecurity of not making it as a footballer. Even when I opened Aubergine at the age of 26, I was still running away from the hurt of football. But I was also getting better at something I was enjoying and I had realised early on that I wanted to be one of the best.”

There have been other tough times. When Tana failed to get pregnant after trying for two years, they had tests which revealed that Ramsay has a low sperm count, apparently owing to years near a hot stove, while Tana has polycystic ovary syndrome. “It was hard emotionally. We were both starting to lose self-esteem and at one stage we contemplated adoption. But because we both had a problem it was easier to work at together; we were both at an all-time low in terms of how inadequate we felt. When Tana finally got pregnant on the third attempt at IVF it was brilliant, and then soon after we had the twins, also through IVF. The big surprise was Tilly, because we had just let things get back to normal.”

“I want the kids to know there is a God”

The twins' birth, six weeks prematurely, was also traumatic. The babies went into intensive care and Jack was found to have a small hole in his heart, which should heal in time. At times like this Ramsay prays. He went to a Church of England school and about six times a year the family go to the church in Chelsea where he and Tana married in 1996. “I want the kids to understand that there is a God and that more times than not we need to turn to Him for help. I've got no reason to stop being religious because so far it's worked.”

After his superfit footballing years, Ramsay's appetite for exercise waned until he was 31, when a friend ordered him on to the scales after a game of squash. He was nearly 18st and had a “horrendous stomach”. Since then he has taken a characteristically macho approach: he boxes in his basement gym, runs to work and he trained for last week's London Marathon in a weighted jacket (he did it in 3hr 45min). And these days he never leaves home without his skipping rope since the boxer Ricky Hatton showed him a brilliant technique (three-minute rounds: one minute fast; one minute criss-crossing his arms; one minute on one leg).

He's down to 15st, looks lean for 6ft 2in, and has a super-healthy heart rate and cholesterol levels. He says endurance exercise helps him to de-stress.And he is keen to set a good example to his children; he hopes they will do part of the London to Brighton bike ride with him in June. “We don't go through this whole PlayStation bullsh** about idle kids,” he says. “Active bodies have active minds. I don't want them going off into cyberspace when they've got to focus on swimming, riding bikes and playing the violin.”

He tries to be a different kind of dad from his father. It helps that his father-in-law, Chris Hutcheson, who is also his business partner, is “the perfect role model and a phenomenal father figure”. He says: “I don't want to be in the position with Jack that I was with my father where, if things went pear-shaped, he would say ‘I told you so!' My father taught me a lot; everything he did I've done the opposite.”

Gordon Ramsay's Healthy Appetite (Quadrille, £20) is published on May 4 and is available from Times BooksFirst for £18, p&p free: 0870 1608080 or visit timesonline.co.uk/booksfirst

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