CAKE ALERT

Junkie food:

• 08 September 2010 by Bijal Trivedi
• Magazine issue 2776. Subscribe and save

Is that cupcake an innocent indulgence? Or your next hit? We're finding that a sweet tooth makes you just as much an addict as snorting cocaine

SETTLED on the sofa watching the usual rubbish on TV, I notice that predictable, uncontrollable, nightly craving. At first I sit there, fighting it. But the longer I fight, the worse it gets. After 20 minutes, I can't concentrate on anything, I feel anxious, and start fidgeting like crazy. Finally, admitting my addiction, I break. I go to the freezer - to my stash of white stuff - and take a hit. Almost instantly, I relax, my brain in a state of bliss as the chemical courses through my veins. Isn't it amazing what a few scoops of ice cream can do?

Before you dismiss my agitation as mere weakness, consider this: to my brain, sugar is akin to cocaine. There is now compelling evidence that foods high in sugar, fat and salt - as most junk foods are - can alter your brain chemistry in the same way as highly addictive drugs such as cocaine and heroin.

The idea, considered fringe just five years ago, is fast becoming a mainstream view among researchers as new studies in humans confirm initial animal findings, and the biological mechanisms that lead to "junk-food addiction" are being revealed. Some say there is now enough data to warrant government regulation of the fast food industry and public health warnings on products that have harmful levels of sugar and fat. One campaigning lawyer claims there could even be enough evidence to mount a legal fight against the fast food industry for knowingly peddling food that is harmful to our health, echoing the lawsuits against the tobacco industry in the 1980s and 90s.

"We have to educate people about how their brains get hijacked by fat, sugar and salt," says David Kessler, former commissioner of the US Food and Drug Administration and now a director of the Center for Science in the Public Interest, based in Washington DC. With obesity levels rocketing across the world, it is clear that I am not alone in my love of sweet things, but can it really be as bad as drug addiction?

We have to educate people about how their brains get hijacked by fat, sugar and salt

Arguably, it was the weight-loss industry that first introduced the idea to the public, long before there was any scientific evidence for it. For example, in her book Lick the Sugar Habit, published in 1988, the self-confessed "sugarholic" Nancy Appleton offered a checklist to determine whether you, too, are addicted to sugar. Since then, the notion has become commonplace.

In 2001, intrigued by this nascent cultural phenomenon, neuroscientists Nicole Avena, now at the University of Florida in Gainesville, and Bartley Hoebel at Princeton University, together began exploring whether the idea had a biological basis. They started by looking for signs of addiction in animals that had been eating junk food.

Hooked on sugar

Sugar is a key ingredient in most junk food, so they offered rats sugar syrup, similar to the sugar concentration in a typical soda beverage, for about 12 hours each day, alongside regular rat feed and water. After just a month on this diet, the rats developed behaviour and brain changes that Avena and Hoebel claimed were chemically identical to morphine-addicted rats. They binged on the syrup and showed anxious behaviour when it was removed - a sign of withdrawal. There were also changes in the neurotransmitters in the nucleus accumbens, a region associated with reward.

Crucially, the researchers noticed that the rats' brains released the neurotransmitter dopamine each time they binged on the sugar solution, even after having eaten it for weeks (Neuroscience & Biobehavioral Reviews, vol 32, p 20). That's not normal.

Dopamine drives the pursuit of pleasure - whether it is food, drugs or sex. It is a brain chemical vital for learning, memory, decision-making and sculpting the reward circuitry. You would expect it to be released when they eat a new food, says Avena, but not with one they are habituated to. "That's one of the hallmarks of drug addiction," she says. This was the first hard evidence of a biological basis for sugar addiction, and sparked a slew of animal studies.

Those results were among the most exciting news in obesity research in the last 20 years, says Mark Gold, an international authority on addiction research and chairman of the psychiatry department at the University of Florida College of Medicine.

Since Avena and Hoebel's landmark study, scores of other animal studies have confirmed the findings. But it is recent human studies that have finally tipped the balance of evidence in favour of labelling a love of junk food as a proper addiction.

Addicted brains

Addiction is commonly described as a dulling of the "reward circuits" triggered by the overuse of some drug. This is exactly what happens in the brains of obese individuals, says Gene-Jack Wang, chairman of the medical department at the US Department of Energy's Brookhaven National Laboratory in Upton, New York. In another landmark study published in 2001, he discovered a dopamine deficiency in the striatum of the brains of obese individuals that was virtually identical to those of drug addicts