KitKats, Jelly Babies, Maltesers, Krispy Kreme doughnuts ... Until 18 months ago, these were the designer Anya Hindmarch’s drug of choice. Her love of chocolate was such that she even created a Cadbury’s Dairy Milk handbag and the firm sponsored several of her events. And, like any addict, she could not admit how strong her dependency was until she reached breaking point.

“I can remember the moment I realised that I was in the grip of a sugar disorder,” she says. “It was a weekday afternoon, and I had just driven back to my office in Battersea from a meeting at Heathrow. The appointment had overrun, and yet again I ended up missing out on lunch. When I stepped into my office, I went into overdrive, searching through my desk drawers, shelves, pockets, anywhere there might be a stash of chocolate. Nothing. I was feeling empty, dead tired, jittery, headachey and desperate for something that would give me a lift. I found myself laughing out of control about the absurdity of my situation. I craved sugar, I had to have my fix, a KitKat or, failing that, a cup of sugary tea. I realised my staff were looking at me as though I was crazy. That was when it dawned on me that sugar was controlling my life.”

At the time, the 36-year-old Hindmarch, who heads a business with a turnover of about £20m and 27 shops worldwide, had crushingly low energy levels. She had just given birth to baby Otto and had awarded herself a maternity leave of five days. “Increasingly, I was relying on sugar to give me an energy rush when I needed it most, and that never failed me, but an hour or so later, I would experience a crashing low and I would find myself craving another sugar high.

“I was also travelling extensively and jet lag, combined with an endless round of airline-standard white bread rolls, was doing nothing to help matters. I would come home on a Friday evening and satisfy my cravings for carbs and sugar, then the next morning, I would have terrible headaches, a real sugar hangover.”

Hindmarch had tried many diets in the past, but each new healthy-eating plan would fail because she couldn’t resist chocolates and doughnuts. She decided to read up on the subject of blood sugar and that’s when she came across the GI diet.

“I realised I was being controlled by sugar, so I switched to eating low-GI foods and noticed an immediate change in my energy levels. I felt as though I’d been set free, because I was no longer thinking about where my next sugar fix was coming from. These days, my head might still crave a biscuit, but at least it’s not a chemical craving any more. Previously, I would have a biscuit and then have a crash, so I would eat another biscuit, and all that seesawing between high and low all day long was exhausting. I thought it was because I was busy, or just weak- willed, as I craved only the bad things, but, in fact, it was my body chemistry that craved what it needed — blood sugar.

“The human body is clever: if you skip breakfast and have low blood sugar, it will crave the food that will raise it most quickly and effectively. I have never done drugs, but I imagine that what I experienced when I ate my first cinnamon whirl of the day must be similar to the kick an addict gets with their first hit.”

Now, Hindmarch finds that she works more effectively, concentrates better and has a lot more balanced energy throughout the day, leaving her with plenty to spare for her family in the evenings. The only food she has in her office is fruit, and there has been a knock-on effect on the eating habits of the staff. To remove temptation from their boss, chocolate is banned, so her employees have to sneak out for a “Twix break” on the pavement. “Eating healthily can be tricky if you’re busy,” says Hindmarch. “Before, I would send out for sandwiches if I was working late. But they’re not a great source of energy. Now, I’m more likely to have roast chicken and a salad.”

She hasn’t put her children, who range in age from 18 months to 16, on the diet, but has introduced them to GI options that provide more energy. “Kids need fuel, and now that I know more about how we are controlled by sugar, I give them wholemeal toast and peanut butter instead of white Mother’s Pride and jam, and fruit instead of a Jammie Dodger. Ultimately, the GI plan is not really a diet, it’s just sensible eating.”

Although weight loss was not her primary motive, Hindmarch has lost pounds as a consequence of eating more healthily. “I believe products containing refined sugar should carry a government health warning,” she says. “People have no idea what sugar is doing to their body.”

AN ALPHA DIET

Not surprisingly, there is a host of celebrity names in the GI gang. Kylie Minogue credits her flawless skin to the wonders of avoiding high-GI foods. She often stocks up on staples such as sugar-free orange and ginger jam.

Another devotee is Sex and the City’s Kim Cattrall who, at 48, is another example of the eating plan’s anti-ageing benefits. She takes an organic chef with her on set, and favours skinless chicken or turkey with raw fruit and vegetables.

The personal trainer Matt Roberts puts all his celebrity clients, including Naomi Campbell and Natalie Imbruglia, on a GI-regulated eating programme, and follows a GI plan himself. “The great benefit of eating low- and moderate-GI foods is that they stabilise blood sugar and, therefore, reduce sugar cravings. If, like me, you want to have enough energy at the end of a long day to work out, it is ideal.”

The Olympic rower Steve Redgrave is also a fan: “I developed diabetes just before I won my fifth gold medal and it was a real shock to me. I need to be very careful about what I eat and keep my blood-glucose levels stable.”

Other GI fans include Bill and Hillary Clinton, the chef Antony Worrall Thompson and the actress Kelly Preston.

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