First day of the four-week sugar detox is a typical failure. I am late. I have to catch a train and I haven’t eaten breakfast. At this point I would usually have a vanilla latte and flapjack. Instead, I seek a no-sugar breakfast. A sandwich, perhaps? Seems weird. A protein hit in the shape of turkey, chicken or prawns? Gross. Plus, I’m sure there’s some sugar lurking in that sliced bread. Muesli. Pain au chocolat. Fruit. Can’t have any of them. How am I going to do this.

Then I see a packet of nuts. Nuts! I can eat nuts! I would not usually eat nuts for breakfast. But this is an extreme circumstance. If I eat the £3 worth of nuts I’ve bought (in a relatively small packet), I will have consumed 1,545 calories. This is worrying. I pick up a bottle of water next to the till. It’s only as I’m walking out that I realise it’s flavoured and has half a gram of sugar in it. Damn. This is going to be difficult.

Completely eliminating sugar from a diet seems extreme. But that’s what certain experts are advocating. In the US they call it a “sugar divorce”, named after San Francisco-based blogger Suzanna Stinnett’s book. “We are a nation addicted to sugar and addiction is your brain twisting the truth,” she wrote. Last year, Paul van der Velpen, the head of Amsterdam’s health service, said: “Just like alcohol and tobacco, sugar is actually a drug. This may seem far-fetched, but sugar is the most dangerous drug of the times and can still be easily acquired everywhere.”

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The warnings are no less dire here. The World Health Organisation (WHO) recommends our intake of “free sugars” (those added to foods by the manufacturer or consumer) should be 10 per cent of our daily calories – or 10 teaspoons a day – but last month, a study by Newcastle University advised that in the UK we need to halve that to five teaspoons. “Treats traditionally saved for birthdays or Christmas have become everyday staples,” warned Paula Moynihan, professor of nutrition and oral health at the university.

But what does this reduction mean in reality? If you’re drinking an Innocent fruit smoothie, that’s six teaspoons in one 250ml bottle. There’s a bit more than that in a 330ml serving of Tropicana Orange Juice. There are about 10 teaspoons of sugar in a can of Coke. But that’s all quite obvious and easy to avoid; what about all the hidden sweetness? Tomato ketchup. Ready-made soups. “Low-fat” foods bulked out with sugar. Plus all the “healthy” foods with surprisingly high amounts of sugar: yoghurt, granola bars, salad dressing, canned fruit, pasta sauces, bottled teas, sorbet… It’s endless.

This is not the stuff that worries me, though. My sugar intake is much worse than a few smoothies. I wish it was smoothies. My problem is snacking, over-eating and replacing meals with processed foods. I will happily replace breakfast with a KitKat at 11am or eat a load of biscuits and doughnuts mid-afternoon because I forgot lunch. When you’re 21 and hungover, it’s OK to have a doughnut for breakfast. You have your whole life ahead of you to eat healthily. When you are 40 (as I was last birthday), suddenly there is not so much time to play with. Plus, several friends have had diabetes warnings. It would be weird if I wasn’t next.

I have been on diets on and off over the years, but sugar always creeps back in, and I find wrappers in my handbag from stuff I’d forgotten I’d bought, let alone eaten. So I wanted to see if I could cope with a month off sugar. No sweets, no desserts, no cake. Maybe even no fruit.

For the layperson, the information about sugar is increasingly confusing. What I know is that it’s not possible to avoid it completely, because it’s not really possible to live without consuming carbohydrates.

Last year, the WHO recommended a cut in the amount of sugar in our diets, following reviews of the scientific evidence of its link to obesity; many in the anti-sugar brigade now contend that sugar is a direct cause. However, the food industry and many academics argue that the problem stems from eating too much of everything, not just sugar. Professor Jim Mann, part of the WHO review, said that sugar “unquestionably contributes to obesity”, but added: “I don’t think sugar is the cause of all evil. It’s an important factor and if we’re eating more sugar and less fat then we need to take note of it.”

The sugar war has stepped up a notch in the past year with Dr Robert Lustig’s Fat Chance: The Bitter Truth about Sugar. The book grew out of a 90-minute video with four million YouTube hits in which he argues that we wrongly demonise fat. An American paediatrician who specialises in treating overweight children, Lustig claims that, “Added sugar is 11 times more potent at causing diabetes than general calories.” For him, the only way forward is to “rid sugar from your diet”.

A lot of Lustig’s arguments are inspired by the prevalence of high-fructose corn syrups (HFCS) in processed foods in the US. “A much cheaper version of table sugar, it is used in many commercial foods, and has an immediate, measurable affect on blood sugar, insulin and fat storage,” explains nutritional therapist Henrietta Norton. This has been shown to contribute to “fatty liver disease”. To avoid HFCS completely means following a diet “as nature intended – if you can’t pick it, dig it or catch it, don’t eat it”. Put in layman’s terms, the syrup is a cheap sugar substitute used to make food taste better. It delivers the hit faster and more effectively, making you immediately crave more. Lustig argues that this addictiveness makes sugar the most dangerous thing for us: we soon become unable to stop eating it.

Many nutritionists, though, are circumspect about Lustig’s claims. They point out that HFCS is not widely used here and that UK consumption of sugar has not risen that dramatically recently. According to the British Nutrition Foundation (BNF), over the past 30 years it has remained at around 115g a day for men and 88g for women. (Though Norton disagrees: “Sugar consumption has gone up by 31 per cent in 20 years,” she says.) The BNF further considers the case that sugar is “toxic” and Lustig’s argument that it has similar properties to alcohol to be unproven. “Food and drinks that are high in sugar and/or fat should be consumed in limited amounts,” it concludes. “But there is no need to completely cut these foods out of a healthy and balanced diet.”

I turn to the NHS, thinking it might give me a bit of leeway. But no. “Most adults and children in the UK eat too much sugar,” intones its website. “Choose wholegrain breakfast cereals, but not those coated with sugar or honey.” k Done that. Been having Bran Flakes every morning. (I later discover they contain sugar. D’oh.) “If you like fizzy drinks, try diluting fruit juice with sparkling water.” I imagine this said in the voice of Fatfighters’ Marjorie from Little Britain. “Swap cakes or biscuits for a currant bun.” Do they know how many currant buns I can eat?

"By week two, I’m actually quite happy not eating sugar. Though even now, I’m not being strict: I’m avoiding fruit juices but I have eaten some bananas. So sue me"

A week into detox and my attitude towards avoiding sugar is yo-yo-ing like crazy. On the one hand, it’s easier than I had thought it would be: just don’t eat sugar. I’ve rediscovered cheese, bread (home-baked, to avoid refined sugar), vegetables and popcorn. I’d forgotten about falafel. I love falafel! Foccaccia has no sugar in it! Hurrah! When I eat out, I enjoy it so much more because I’m not thinking, “I’d better not have a starter because then I can’t have a dessert.”

On the other hand, the urge for sugar has not receded. I still have to remind myself to avoid vanilla lattes and ubiquitously proferred biscuits. I bite into a mini mince pie by mistake and have to decide whether to spit it out. (I eat it. But not the whole thing.)

By week two, I’m actually quite happy not eating sugar. I never thought I’d say that. This is why diets are useful: it’s not about what you eat, it’s your attitude to it. But how can I make that mental shift stick? Even now, I’m not being strict: I’m avoiding fruit juice but I have eaten some bananas. So sue me. (Henrietta Norton: “Fruit has no immediate impact on our blood sugar or insulin levels when eaten in moderate doses.” So, as long as you’re not overdosing on smoothies or fruit juices, you’re fine.)

Alcohol is a tricky one. I decide it’s OK to have the occasional glass of wine (1g of sugar) or fizzy wine (2.5g) maybe once or twice a week (come on – I’m doing this during the Christmas party season), but I’m avoiding so many things anyway that it’s not that difficult to not drink. I could have gin or vodka with soda water but I decide that is a slippery slope. More importantly, I worry that drink might impair my judgement and make me more likely to seek out doughnuts.

By week three (I discover almonds!), the experience has convinced me that there is a good case for sugar detox for some people. My moods have improved. I don’t “crash” and crave a sugar high in the afternoon. A skin irritation on my face has cleared up.

Having kicked cigarettes 15 years ago (40 a day at one point) and cut down on my drinking over the past 10 years, I have a theory that slowly but surely these noxious habits have been replaced by a more socially acceptable one: eating sugar. Cutting out sugar for a month gave me a new habit: checking ingredients panels for sugar content. But what it really gave me was an awareness of when I want to eat and how to avoid getting so hungry that I just eat any old junk.

The nutritionist Ian Marber says it’s not wrong to use the word “addictive”: “Sugar triggers the reward system. That’s the dopamine. You have a pleasurable experience and you have a glucose high which gives you energy.” It sounds great. He adds: “The problem is, when you have an excess it is stored away.” Hello, my body. “And that happens quite dramatically so you feel hungry again quickly.” So is total avoidance the only way around this? “To avoid any food 100 per cent is really difficult. It gets you into a mode where you think, ‘I’ll be good in January.’ But by February you’re less motivated. Find something you can manage and do it all the time. Take the drama out of it.” Semi-avoidance I can manage.

By week four, this is what I’m heading towards. Sugar and I are not quite divorced: I have half a glass of pink lemonade. But we’re separated. The other party keeps begging for a reconciliation, but I kind of like it on my own. It turns out, the question is not what should we be eating – we all know the answer and most of us are able to ignore the (sensible) answers to it – but how do you maintain common sense when surrounded by temptation?

The inability of many of us to find an answer to this question is what makes us overweight. But – guess what? – my four-week sugar detox started to solve it. The key to eating what you should be eating and being a healthier weight is that it’s all in the mind. If you can fool yourself that you don’t need to eat a certain food group and “train” yourself to avoid it, you save a lot of time and procrastination. I’m not sure I will be able to think for life that “I don’t eat sugar”. But I can manage to think – and live – the idea that I don’t eat sugar most of the time.

Oh, and by the way, despite the cheese and the foccaccia and the 1,545 calories of nuts, I lost 5lb in four weeks. Why? You just can’t eat as much cheese and bread and nuts as you can cake and chocolate. It was worth it just to find that out.

Sugar by the numbers

2,250,000: The UK’s annual consumption, in tonnes, of sugar, about three-quarters of which is sold direct to industrial users, such as soft-drinks and confectionery manufacturers. Source: Defra

100: The percentage increase in consumption of fizzy drinks in the UK in the past 15 years. Source: Food Standards Agency

13.5: The percentage of our energy intake derived from non-milk extrinsic sugars –those ingested via preserves, non-low-calorie soft drinks, honey, confectionery etc. Source: Family Food 2012

One-third: The proportion of British under-nines thought to be clinically obese (for British male and female adults, it’s one-quarter). By 2050, this figure is predicted to rise to half the population. Source: NHS, Foresight study