22 March 2011

Junkie food

There is compelling evidence that foods high in sugar, fat and salt can alter your brain chemistry in the same way as highly addictive drugs such as cocaine and heroin.


A delicious indulgence, or your next desperate hit? Reader's Digest's Bijal Tirivedi investigates.

Settled on the sofa watching TV, I notice that nightly craving. The longer I fight, the worse it gets. After 20 minutes, I can’t concentrate, I feel anxious and fidget. Finally 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?

To my brain, sugar is akin to cocaine. There is 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.

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.

With obesity levels rocketing across the world, it is clear I am not alone in loving sweet things, but can it really be as bad as drug addiction?

The idea first surfaced over 20 years ago. In her book Lick the Sugar Habit  first published in 1988, the self-confessed “sugarholic” Nancy Appleton offered a checklist to determine if you, too, are an addict. Since then the notion has become commonplace.

In 2001, neuroscientists Nicole Avena and Bartley Hoebel began exploring whether sugar addiction had a biological basis.

Hooked on sugar

They offered rats sugar syrup, similar to the sugar concentration in a typical soft drink, for 12 hours each day, alongside regular rat feed and water. After a month, the rats developed behaviour that Avena and Hoebel claimed was chemically identical to morphine-addicted rats. They binged on the syrup and showed anxious behaviour when it was removed - a sign of withdrawal. Crucially, the researchers noticed the rats’ brains released the neurotransmitter dopamine each time they binged on the syrup, even after having eaten it for weeks.

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 and sculpting the reward circuitry. You would expect it to be released when they eat a new food, says Avena, but not one they are habituated to. “That’s one of the hallmarks of drug addiction,” she says.

Since this landmark study, scores of other experiments have confirmed the findings. But it is recent human studies that have tipped the balance of evidence in favour of labelling a love of junk food as a proper addiction.

Addiction is commonly described as a dulling of the “reward circuits” triggered by the overuse of some drug. This is what happens in the brains of obese individuals, says Gene-Jack Wang, of the medical department at the US Department of Energy’s Brookhaven National Laboratory.

 In 2001, he discovered a dopamine deficiency in the brains of obese individuals that was virtually identical to those of drug addicts. In subsequent studies, Wang showed that even when (not obese) individuals are shown their favourite foods, an area of their brain called the orbital frontal cortex – involved in decision-making – experiences a surge of dopamine. The same area is activated when cocaine addicts are shown a bag of white powder.

Pleasure surge

Eric Stice, a neuroscientist at the Oregon Research Institute, has been trying to predict a person’s propensity to junk food addiction by watching how people’s brains respond when fed a brief burst of chocolate milkshake.

He found that lean adolescents with obese parents experienced a greater surge of dopamine than those who had lean parents. “There are people born for whom eating is more orgasmic,” he says. As these people overeat, their reward circuitry dulls, which makes the food less satisfying and motivates them to eat more to compensate.

This is precisely what we see with chronic alcohol or substance abuse, says Stice.

Stice has also shown that some people have a dulled dopamine response when eating appetising foods. This places them at greater risk of obesity because they have to eat more to get a sufficiently rewarding level of dopamine release.

Together, these studies suggest there are two routes to food addiction: one if you find food more rewarding than the average person, and another if it isn’t rewarding enough.

Fast food

Of course, fast food is more than a sugar rush, it is often a rich cocktail of sugars, fats and salt. Neuroscientist Paul Kenny, at The Scripps Research Institute in Florida, is probing the impact of a junk food diet on rat behaviour and brain chemistry.

Kenny wondered whether rats that eat junk food would have a similar response to the cocaine-addicted rats he studied. He used three groups of rats. The control group had only standard rat feed. The second group could eat junk food - bacon, sausage meat, icing and chocolate - for one hour each day with regular rat feed and water for the rest of the time. The last group had an all-you-can-eat, around-the-clock buffet that included junk food and rat feed.

After 40 days, Kenny withdrew the junk food. The rats with unlimited access to junk food went on a hunger strike. “It was as if they had become averse to the healthy food,” says Kenny. It took two weeks before they assumed a normal diet.

Unlimited access to an addictive drug like cocaine has a big impact on the brain, says Kenny, so you might expect any addictive effect from food to be much less pronounced. “[But] changes happened rapidly and we saw very, very striking effects.”

Some people now claim that junk foods rich in salt, sugar and fat switch on biological mechanisms that are just as powerful and hard to fight as drugs of abuse. Given we regulate drugs because of the harms they can cause, is it time to begin tougher regulation of fast food, too?

Obesity epidemic

John Banzhaf, a lawyer who in the 1960s won a court ruling that forced US radio and TV stations to provide free airtime for anti-smoking messages, is now turning his attention to the fast food industry and its role in fuelling the obesity epidemic. He believes there is enough research for the US Office of the Surgeon General to issue a report on food addiction, as it did for nicotine addiction in 1988. But he acknowledges this is going to be a tricky fight. “Fast food isn’t a [single] chemical so you can’t meaningfully ask the question ‘Is a triple bacon cheeseburger addictive?’ ” he says. It would have to be something more specific about quantities of sugar, salt and fat.

Signs of things to come can be seen. Trans fats were recently banned in restaurants in New York and throughout California; Woolworths is leading the supermarket charge against transfats and salt in South Africa; and fizzy drinks are being taken out of some school vending machines.

Unsurprisingly, the food and drink industry is putting up a fight. These foods are only addictive to a “certain subset of consumers who don’t exhibit the discipline required,” says Hank Cardello, a former executive at food companies including Coca-Cola, and now a visiting fellow at the Hudson Institute, a think tank in Washington, D.C. “People aren’t going to change their behaviour. To me it’s about getting kilojoules off the streets.”

He believes tax relief for companies producing low-kilojoule foods is one strategy that wouldn’t destroy the companies that sell fast food. Kessler points out, of course, the ultimate power is in the consumers’ hands.

I can vouch it is possible to break the habit. After two weeks of cold turkey, I can report I have successfully kicked my ice-cream habit. If only I could kick my junk TV addiction…

From New Scientist, September 4, 2010 © New Scientist, London; published by Health24 courtesy of Reader’s Digest.

- (Health24, March 2011)

Read more:

Quiz: am I eating too much sugar?
Sugar myths and facts
The psychology of food cravings


Read Health24’s Comments Policy

Comment on this story
1 comment
Comments have been closed for this article.

Live healthier

Exercise benefits for seniors »

Working out in the concrete jungle Even a little exercise may help prevent dementia Here’s an unexpected way to boost your memory: running

Seniors who exercise recover more quickly from injury or illness

When sedentary older adults got into an exercise routine, it curbed their risk of suffering a disabling injury or illness and helped them recover if anything did happen to them.