Here’s an experiment you may or may not wish to try at home. Instead of your evening meal, have a large bar of chocolate. Or something with equally high sugar content: ice cream, chocolate biscuits, sweets. Note your mood before and after. Chances are you’ll have gone from feeling normal to feeling headachy, irritable, vague, lethargic, even a bit depressed.

The next morning you may even feel slightly hung over: thirsty, grumpy, spaced out. Welcome to sugar crash. We don’t need our sugar to be fermented in wine bottles for it to adversely affect our minds and bodies.

Obviously, most people would not have a large amount of chocolate in place of a meal. Nor is this about food guilt or self-flagellation for eating “bad” food. It’s about the effect refined sugar has on us physiologically.

It’s not good.

And although brown rice whole food freaks have been saying it for years, it seems as though the rest of us might be finally waking up to the fact that (a) sugar is addictive and (b) sugar is harmful. While debate continues over whether it is ever accurate to call sugar a poison or a toxin, its link with widespread obesity and diabetes is impossible to ignore.

We in the West have long beaten ourselves up about the widening obesity crisis. It’s our own fault for being greedy, lazy couch potatoes. We are so busy exercising only our fingers and thumbs on computer keyboards and games consoles, punctuated by breaks for cake washed down with giant buckets of fizzy drink, that we have become a society of elephant seals, honking self-pityingly about our ballooning size as we do nothing about it.

Except that this is not quite an accurate picture. Yes, we are definitely fatter—on average, 25 pounds heavier than we were in the ’60s—but not necessarily less active. Researchers at Plymouth Hospital, in a 12-year-long Early Bird study, began monitoring 300 five-year-olds in 2000, and found that although one in five was at risk of developing Type 2 diabetes (previously a condition that affected older or middle-aged people), these kids were just as physically active as children 50 years ago. So what was it that was making them so prone to develop it?

Could it be sugar? Well, yes. The 1923 Nobel Prize winner for medicine who discovered insulin, Canadian physician Frederick Banting, began to notice that in societies where sugar consumption was low, diabetes was rare. It used to be quite rare in the West, too, but this began to change around the turn of the last century. A 15-fold increase in deaths from diabetes was reported in New York between the American Civil War and the 1920s, according to research conducted at Columbia University; this particularly escalated between 1900 and 1920, when some American cities saw four times more people dying of the disease. This surge in diabetic death coincided with a huge increase in sugar consumption as the sweets and fizzy drinks industries began to take off.

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Fast forward to now. Robert Lustig is professor of pediatrics at the University of San Francisco and director of WATCH (Weight Assessment for Teen and Child Health). He is, in other words, a world expert on fat kids, and is one of the very few medical professionals unafraid to use the word “poison” in connection with sugar.

When we think of poison we probably think of arsenic or thallium or belladonna, which are all fast and dramatic, but what about a slower poison? Alcohol has been called “the slow poison” (by people like Shaun Ryder, who, it would be reasonable to say, knows his poisons). But how can we include chocolate or lemonade in that category? Isn’t that the kind of hysterical hyperbolic labeling favoured by seaweed-eating macro-neurotics and food obsessives?

In 2009, Robert Lustig gave a lecture called Sugar: The Bitter Truth. Since it was posted on YouTube, it’s had 2,602,506 viewings, which is a lot for a 90-minute medical talk. Lustig’s point is not that sugar is full of empty calories—we know that, everybody knows that—but that it is metabolized differently from other foods. And not in a good way.

Not all calories are equal. The body treats fructose differently from glucose. In other words, starchy foods like potatoes and bread are not metabolized in the same way as the same calorific amount of sugary food. Starch, that is, glucose, is metabolized throughout the whole body, whereas sugar fructose and glucose are processed only by the liver. Lustig calls this “isocaloric but not isometabolic”: same calories, different chemical reaction in the body, and therefore different consequences.

The sugar to which Lustig refers is sucrose, the stuff we may or may not stir into our tea, and fructose, which is found in the food additive high fructose corn syrup (HFCS) that’s in lots and lots of the everyday foods we eat. Once sugar has entered the body, it is dealt with by the liver; if you down a can of orange soda or a glass of orange juice, the liquid sugar hits the liver much faster than if you eat, say, whole oranges to get the equivalent amount of sugar. If the liver has to deal with a significant amount of rapidly incoming sugar, it does what we would rather it didn’t: it converts the sugar to body fat. Fast.

This results in something called insulin resistance, which is the underlying problem both in obesity and in the development of type 2 diabetes, and is also thought to be connected to the development of quite a few cancers. No wonder Professor Lustig is so adamant that sugar, far from being a sweet, rewarding treat for children, is a deadly poison that’s shortening the lives of millions of us.

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But sugar has been around forever, hasn’t it? Yet we have only been obese for a few decades. So it still must be our own fault for being greedy, super-sized fatsos. Isn’t it?

Not according to British writer and broadcaster Jacques Peretti, who recently made a series unambiguously titled The Men Who Made Us Fat. It’s all about politics, economics and the massive amounts of HFCS added to our food.

You may not have heard of Earl Butz, but he is very much connected with the size of our, well, butz. He was a Secretary of Agriculture in the Nixon Administration who in the early 1970s suggested to farmers that they grow corn in industrial quantities in the hope of bringing down the cost of food (and therefore helping Nixon get re-elected). The farmers duly complied. Powered by mega-production of corn, American food became cheaper: cows ate it and were turned into burgers; chips were fried in its oil. And there were loads left over. By the mid-1970s, America was up to its ears in surplus corn.

Earl Butz went to Japan to investigate the processing of all this corn into a liquid sugar. This liquid was cheaper than cane sugar (the traditional food baddie we have long been told to avoid), and even sweeter. HFCS, known as glucose-fructose syrup in Ireland and Britain, began being manufactured and added to our foods on a vast scale.

Cheap and super-sweet, this stuff adds shelf life, sweetness and a sugary surface sheen to baked foods. But its presence is not restricted to foods you’d normally associate with sugar, like desserts and sweets. HFCS is squirted into everything: processed meats, cooking sauces, cole slaw, bread, TV dinners, pizza, fizzy drinks, fast food, breakfast cereals, ketchup, yogurts, ice cream (even the premium stuff), salad dressing, cakes and biscuits, jam, and a lot of low-fat food products—in fact, anything remotely processed. Cheap added sugar made food taste better, last longer, and sell at lower cost; from a food industry perspective, what was not to like?

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Until the advent of mass-produced HFCS, fat was the number one food enemy. Fat made you fat, raised your cholesterol levels, blocked your arteries and was generally “bad.” Low-fat became the buzzword. Foods were prefixed with descriptions like lo-, lite- and diet-. Anything under 5 percent was categorized as “low fat.” But fat makes things taste nice, as any butter-happy cook will tell you. So how to replace the fat?

With sugar. Lots of it. The soft drinks industry was already sugar-tastic when in 1984 Coca Cola switched from traditional sugar to HFCS. With Coke being the dominant brand, everyone else followed suit. HFCS was cheaper and sweeter and nobody had ever heard of obesity crises or sugar addiction.

While researching heart disease in the 1970s, one British academic, Professor John Yudkin, had made a case for sugar making us fat and getting us hooked. Nobody listened. Everyone was too busy demonizing fat. The food industry knew quite well that there was far more profit to be made from categorizing fat, rather than sugar, as the enemy. Low-fat or fat-free was a far more enticing consumer option than anything sweetened with weird chemical stuff that was being linked to cancer in lab rats. So we were sold the sugar good/fat bad equation.

These days our food is saturated with sugar, our taste buds have adjusted accordingly, and we are carrying on average an extra 25 pounds. So the obvious solution would be to knock sugar on the head. Just give it up. Stop using it. Simple.

If only. The concept of food addiction is a new one. We can become addicted to substances—drugs, alcohol, tobacco—or behaviors like gambling. But food?

Yes, food—specifically, refined sugars, which are still a novelty in the human diet in evolutionary terms. According to research done in 2007 at the University of Bordeaux, intense sweetness triggers more of a neurochemical pleasure response than cocaine.

Here’s what the researchers said: “In most mammals, including rats and humans, sweet receptors evolved in ancestral environments poor in sugars and are thus not adapted to high concentrations of sweet tastants. The supranormal stimulation of these receptors by sugar-rich diets, such as those now widely available in modern societies, would generate a supranormal reward signal in the brain, with the potential to override self-control mechanisms and thus to lead to addiction.”

At Princeton in 2008, Professor Bart Hoebel had a look at rats and sugar bingeing, and noted changes in their brain chemistry that were the same as changes produced by morphine, cocaine and nicotine.

“If bingeing on sugar is really a form of addiction, there should be long-lasting effects in the brains of sugar addicts,” he said. “Craving and relapse are critical components of addiction, and we have been able to demonstrate these behaviors in sugar-bingeing rats in a number of ways.”

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Never mind rats. As a card-carrying sugar addict, I can vouch for the addictive responses sugar causes, responses that override good intentions, self-knowledge, will power, the loss of self-esteem caused by weight gain, even threats to physical health (like diabetes, cancers and heart disease). The cycle of addiction: obsession and craving, caving in and using, remorse and shame, passage of time, more obsession and craving, more caving in and using, happens with sugar, too. Ask any diet breaker: nobody has these issues with broccoli. Nobody binges on tofu.

My own sugar addiction emerged when I stopped drinking and subsequently robbed my dopamine receptors of their major daily sugar intake. I am far from unique: overnight sugar madness is a common trait in recovering alcoholics. But glance around and you see that you need not be sugar-sensitive (as in alcoholic) to be sugar-addicted; the size of our bodies on any high street makes that obvious. We are all sugar addicts now. One nibble and you’re nobbled.

For sugar addicts, writes Dr. Kathleen DesMaisons, author of The Sugar Addict’s Total Recovery Programme, “It’s like having two different people live in your body. From one moment to the next, your sensitivity and openness turns to moodiness and irritability. This emotional ping-pong remains inexplicable without an understanding of sugar sensitivity.”

Thankfully, knowledge is power. Just as recovering alcoholics avoid all alcohol so that they don’t trigger a craving, the same wisdom applies to sugar addiction. Except it’s much, much harder. While being a drug addict is socially unacceptable, and being an alcoholic less so because booze is a legal social drug, being a sugar addict is not only acceptable but positively encouraged. Go on, have some. You know you want to.

And because sugar is so prevalent in food, radical diet change can be hard to initiate. Food recovery groups like Overeaters Anonymous and Food Addicts Anonymous advocate a diet free of refined sugar (especially when combined with refined flour), which requires constant dedication and vigilance.

Sugar is everywhere. Only when the social and financial cost of our consumption of sugar outweighs the profits made by the high-sugar processed food industry is it possible that we will see an emphasis on industry responsibility rather than on blaming the individual for being fat, stupid and lazy. We no longer drink fizzy drinks laced with cocaine, or think that smoking is cool. But with Coca Cola and McDonald’s recently sponsoring the healthiest event on earth, the Olympics, this U-turn at the source may still be some time away.

Suzanne Harrington contributes to the Irish Examiner and the Guardian, among other publications.