Gillian McKeith interview: Fighting fit

Apparently, her 14-year-old daughter Skylar keeps her up to date with the latest sounds, and along with eight-year-old Afton, they like nothing better than to dance about McKeith's London home. "We put on the iPod and dance like crazy, jumping on the units. It's brilliant. I love dancing," says McKeith. "As well as the Ting Tings, I like Katie Melua, Take That, the Jonas Brothers, Girls Aloud and Paolo Nutini. Well, my daughter uploads them, so they're her choices, really."

With best-selling books and TV shows including Channel 4's You Are What You Eat, it's perhaps no surprise that the evangelical McKeith has hit on the medium of music to help spread her healthy-living message. That said, it's not immediately obvious how funky beats will help promote a regime of exercise, fruit, veg and fish, not to mention detoxing and colonic irrigation.

Her 30-minute Walking Workout downloads come in a choice of 1970s disco, 1980s Top 40 and Girl Power hits. All very easy on the ear, but just when you think she might have gone soft, she points out the name of her latest book – The Boot Camp Diet: 14 Days to a New You. And then you hear that familiar voice, breaking into Madonna's 'Give it 2 Me', barking instructions and dispensing nutritional advice and encouragement like a martinet. "My daughter said, "You're not going to talk through the songs, are you?' But I am. I say things like, 'Did you know that keeping moving moves your bowels?' and 'Left, right, one, two, no slacking!'." The songs are peppered with Gillianisms, such as "Get that bahookie moving." The tone is somewhere between encouragement and warning.

"Everyone likes music and if you put my voice with it, it will motivate them. There is a dance beat through all the tracks, so you can work out or walk to the beat, getting faster as you move forward. I say forward because I've followed clients and seen them nip round the corner and stop."

Followed? "Yes. I have to or they don't do it. It's like having more children. Some of these people haven't walked in years!"

So Sergeant-Major McKeith is on to you 'orrible lot, and with her voice in your head you won't even be able to think about going awol. Throw in an accompanying book and a website stuffed with recipes and advice, and the guru of poo is waging a war on several fronts at once. So, given the 'boot camp' theme and her rather persuasive personality, does she have military connections? "No, just Brownies and Guides, although my grandfather was in the Black Watch and my father's 19-year-old brother was killed in Holland in the Second World War. When I was young, I hitchhiked alone to Holland to see his grave. I can't believe I did that!"

I can. But for someone who provokes such strong reactions ("Shrew" and "Food fascist" being two of the milder epithets), in person McKeith is much softer and funnier than she appears to be on television. She blames the editing process for her harridan image. "I have a very robust sense of humour and like to laugh. Sometimes it comes across as finger-wagging, but what people see on telly is an edited character. I'm actually much worse!"

McKeith is used to dividing opinions, and is also used to criticism, not least about her qualifications. When challenged, she rattles them off. She has a BA in modern languages and linguistics from the University of Edinburgh, a master's in international relations from the University of Pennsylvania, and another master's and a PhD in holistic nutrition via a distance-learning programme from the American Holistic College of Nutrition. Last year, she was awarded a master herbalist diploma from the Australasian College of Health Sciences. She is a member of the National Association of Nutrition Professionals, a post-graduate member of the Centre for Nutritional Education in England and has certificates from the London School of Acupuncture and the Kailash Centre of Oriental Medicine. Phew!

What about the Advertising Standards Authority asking her to stop using the title 'Doctor' on her advertising, which she did in February 2007? McKeith insists this only related to advertising materials of her products, and that she is free to use the title as she has a PhD in holistic nutrition. "I don't mind people asking questions about my education. I am extremely proud if it, and it is important as a practitioner to always enhance it," she says.

"When you really believe in something and are passionate about helping people to empower themselves and make their lives better, you have to take a stand and accept criticism. But I also get thousands of e-mails and letters from all over the world, from people who have tried my methods, saying they work, and that keeps me going."

McKeith says that she works to make a difference. "The world is in a crisis. Never before have we seen obesity and diabetes on such a scale. Someone has to speak out, and of course there will be people who won't like it – my mum, for instance; she doesn't like to hear it."

Ah yes, her mother. McKeith is on record as saying her mother is scared to come for Christmas dinner. Is she serious? Is her mother too frightened of a Christmas without black bun and shortbread to venture south from Perth? "Yes, she's terrified!" says McKeith breezily.

But does she come? "Yes, she comes. And brings her sausages in a blanket and sits in the naughty corner! I make her aduki bean stew and mung bean casserole, and she tells me to get off my soapbox," she laughs, with a mixture of exasperation and affection.

"She is very set in her ways. I used to find it irritating, but she's a good benchmark. If I can persuade her to accept something, I can persuade anyone. She will try things, though, and is a very big fan of aloe vera juice. She suffers from diverticulitis, from past smoking and a poor diet, and she swears by it for that."

McKeith's children, in contrast, are big fans of her diet. "They grew up with it, and don't know about kebabs."

A recent stay in a Swiss hotel did give younger daughter Afton the opportunity to call room service for pizza, however. And when they didn't have any, she asked them to send out for it. "At seven," laughs her mother, voice filled with admiration at her youngest's initiative. "She's a Mini-me."

While McKeith blames her own mother for her inability to cook, it was she who inadvertently set her off on a mission to "empower people to improve their lives through information, food and lifestyle", says McKeith. "She didn't want me in the kitchen, so when I left home I didn't know how to cook for myself properly and lived on white rice and chocolate clairs."

Three stone overweight and suffering from migraines, fatigue and painful periods, McKeith was introduced to a microbiotic diet by her boyfriend Howard, now her husband, and had an epiphany that set her off on the road to fame and fortune. "We all know the kind of food I grew up with – a typical Scottish diet. We'd have meat three times a day. I certainly never ate a mango, and had no idea what macrobiotic meant."

Is there nothing at all she misses about the Scottish diet? "No!"

Square sausage? "No!"

Scotch pies? "No!"

Pudding suppers? "No!"

Deep-fried Mars Bars? "There's no such thing. I don't believe that. No one would ever eat that."

They do. For the first time in the interview, the ebullient McKeith falls silent. She has never heard of a deep-fried Mars Bar, yet claims to be a nutritionist and a Scot? Now I am doubting her credentials.

McKeith's restlessness can partly be explained by her need to keep moving to deal with the constant pain she suffers from scoliosis, a condition that causes curvature of the spine. Fellow sufferers include Liza Minnelli, John Lydon and Princess Eugenie, who had an operation to correct it in 2002.

McKeith's scoliosis is severe, but was undiagnosed until she had a fall in her 30s – by which time it was too late to operate. A petition on her website calls for spinal testing to be reinstated in schools. "There's not a moment of my life I'm not in pain, but I don't take painkillers. I deal with it by positive thinking, an hour of pilates a day and keeping moving. It could have been avoided if more had been known about it when I was young." As well as compressing her organs, her condition makes McKeith shorter, and she admits to being self-conscious about her height. "I should be six and a half inches taller. The next person who says, 'Aren't you little', I'm going to slap!" she says.

It's also in a bid to cover her back that McKeith wears her hair long. "People make comments about me having long hair at my age (various reports suggest she was born in 1959, but she refuses to confirm this]. Why shouldn't I? My hair is lovely – and it also hides my curve."

Hiding the curve was also the motivation for the gold dress she wore to the 2005 Baftas, which saw her described as "a turkey wrapped in gold BacoFoil". Despite the furore, though, McKeith was delighted. "I never laughed so hard," she says. "Even now when I look back on that day, I laugh my head off. At least at the Baftas Gillian McKeith's back was never noticed or talked about.

"I often wonder if it was a lack of vitamin D, from growing up in Scotland where there's a lack of sunshine, that caused the scoliosis, so I make sure my children get plenty of sun. I dance, exercise and lift weights. I can't do anything more. Well, I could go and live in Spain, I suppose," she suggests half-heartedly. She'll never do that, though. She wouldn't trust us to behave while she was away.

IF HER relationship with her mother is loving but maddening, she found her father Robert much easier to get on with. "My dad passed away three years ago. We were very close, and it's only now that I feel as if I'm starting to deal with it. In fact, I haven't been able to talk about it until now. I really miss him," she says.

"The only thing we ever disagreed on was his smoking. Then, in 1992, he had a massive heart attack and was told he had just two months to live. He stopped smoking and lived until 2005. His last message to me was to tell people never to pick up a cigarette. It might sound a bit trite, but he developed cancer of the oesophagus from smoking, and at the end couldn't eat, couldn't take his heart medicine…" Her voice trails off.

Regardless of the health issues in the McKeith household, it's clear there was no lack of love or interest in Gillian and her younger brother, and the health guru emphasises the importance of having time for people. "Whether they're celebrities or not (McKeith is known to have helped out singers Dannii Minogue and Michelle McManus, but won't discuss other high-profile clients], people appreciate someone taking an interest. Often it's for the first time. I pay them so much attention."

Too much, some might say. No one has ever accused McKeith of lack of input. "I have to open people up to acknowledge emotional issues that often go back to childhood. That's why they cry. Not because I'm horrible to them. One woman I treated had been overweight since she was 13. Her mother died when she was 11, her father remarried and the woman's teenage son raped her. No one had ever listened to her, and she was now 54.

"People tell me things like that all the time. I'm a good listener, and they love talking to me. I have to strip them bare before we can move forward." Note the "move forward". None of that running on the spot, you slackers.

"I need to own you for 14 days. If you want to achieve something, it's no good just longing for it. I've had so many girls longing to be a size 10 or 12, and I say, 'You never will be because you're telling yourself you can't. Try telling yourself you can.' Over 15 years of working with clients in private practice, I'd say the biggest battle is with their own heads. They need a positive message. Say, 'I am slim,' and keep saying it until you are. My books are bossy, but bossy with love."

• Gillian McKeith's Boot Camp Diet (Penguin, 6.99) is published on Thursday. Gillian McKeith's Walking Workout series is available to download at iTunes and www.tescodigital.com from Thursday, 6.32. See www.gillianmckeith.info for details of the Boot Camp Diet online

BOOT CAMP DIET

An ideal day's intake:

Breakfast Warm water with a squeeze of lemon juice.

Smoothie (1 banana; 1 cup strawberries; 1 cup blueberries).

Snack Hummus with carrot and cucumber sticks.

Lunch Salad of mixed sprouts, rocket, cherry tomatoes and avocado, dressed with lemon and olive oil.

Snack Vegetable juice (2 carrots; 1 small beetroot; 2 celery stalks; piece root ginger).

Dinner Lemon sole with mange tout, broccoli and kale.

Snack A small handful of almonds.

Drink 2 litres of water over the day, plus herbal teas such as nettle, fennel, peppermint and lemon balm.