Could food cravings be addiction?

Being overweight in the UAE is no laughing matter. As if carrying extra kilos around in 45 degree heat wasn't bad enough, it seems everyone is on your case.

Customers buy food at a McDonald's and a KFC fast food outlet at the Mercato Mall in Dubai.

Being overweight in the UAE is no laughing matter. As if carrying extra kilos around in 45¿C heat wasn't bad enough, it seems everyone is on your case.

Just last month, researchers identified the Emirates as a nation that must do far more exercise if it is to avoid a host of diseases.

An international study published in The Lancet found that substantial fractions of the notoriously high levels of Type 2 diabetes, coronary heart disease and other ills afflicting the region are attributable to sedentary lifestyles.

Get more exercise, eat better, eat less … the finger-wagging seems endless. Yet as anyone struggling with food cravings during this month of fasting knows, if it were that easy, there wouldn't be a problem.

Now science is starting to put its weight behind a claim long suspected by those struggling with such cravings: some foods aren't merely tasty, they're truly addictive.

The idea that obese people are in the grip of an addiction has had a rough ride from nutritionists, who have demanded hard evidence that some foods aren't just moreish, but are similar to hard drugs in the responses they elicit.

But this month the American Psychological Association's annual convention heard that both animal and human studies are confirming the reality of the classic signs of addiction - craving and withdrawal symptoms - after consuming some forms of food.

The claim was made by Professor Kelly Brownell, the director of Yale University's Rudd Centre for Food Policy and Obesity, one of the world's leading nutritionists and editor of the first collection of research papers on food addiction, published this month by Oxford University Press.

Prof Brownell bases his claim on mounting evidence that some foods contain substances that can trigger a response akin to addictive drugs like alcohol.

Exactly what these substances are remains controversial. While the role of additives such as caffeine and synthetic chemicals remains unclear, most suspicion has fallen on fat and carbohydrates.

As long ago as the early 1980s, researchers found that rats greedily gorged themselves on fats or carbs but ceased if given naloxone, a compound known to block the action of drugs like heroin.

This suggested a link between consuming fatty or sugary food and so-called opioids - chemicals that give morphine-like drugs their addictive qualities.

By the early 1990s, similar effects had been found in studies on human volunteers: foods eaten after a volunteer had been given naloxone were reported as less enticing.

Significantly, however, the volunteers reported no effect on their hunger levels. In other words, the naloxone did not affect when people began eating, but dramatically reduced their tendency to gorge on moreish food.

Within the last few years, researchers have shown that some people may be especially susceptible to the opioid effect of certain foods.

Using brain-scanning technology, Dr Eric Stice, a neuroscientist at the Oregon Research Institute, has recently shown that in susceptible people, simply showing an image of a milkshake was enough to provoke activity in the so-called caudate region of the brain - associated with cravings.

When these people were allowed to taste some of the milkshake, in contrast, they showed virtually no activity in the parts of the brain linked to satiety, or "fullness". That is, they suffered from a double whammy effect of being easily tempted, and hard to stop.

As for signs of real addiction, a team led by Dr Nicole Avena of Princeton University has shown that rats regularly fed on sugar-rich food undergo classic drug withdrawal symptoms such as chattering teeth and tremors when the sugar was withdrawn. The team concluded that, in some circumstances at least, sugar can be addictive.

Inevitably, there has been academic wrangling over the precise definition of addiction in the case of food.

What is not in doubt is that the global obesity epidemic has come at a time of ever more foods containing sweeteners such as high-fructose corn syrup. A quick check of the ingredients in even the most apparently simple foods like bran flakes and bread will reveal them to contain sugar.

Even so, proof of the addictive nature of some foods would not by itself solve the obesity epidemic. What is needed is a strategy that has succeeded where attempts to tackle similar challenges like drug addiction have largely failed.

Many experts, including Prof Brownell, doubt that success can come from the standard means of treating addiction: enforced abstinence or substitution.

Given the huge availability of potentially addictive food, enforced abstinence seems no more likely to succeed than diets generally, which are notorious for their recidivism rates.

As for substitution, the food industry itself has moved towards "healthier" low-fat products - but at the price of hiking up the sugar content.

One obvious step would be to replace sugar with artificial zero-calorie sweeteners. However, there's some evidence that such sweeteners have a similar effect to sugar, biochemically preparing the body for a high-calorie intake, whose failure to materialise prompts cravings for more food.

According to Prof Brownell, research in animals has shown that those given artificial sweeteners in their food more than compensate for the zero calories by overeating, resulting in higher body-fat ratios.

So, if treating those addicted to food is unlikely to succeed, what will? Some experts think the best approach is to focus not on the individual but on the food industry. To date, however, the industry has set its face against measures such as the imposition of "soda taxes" on sugary drinks.

Proof that some foods are addictive could change all that, however. It would result in the food industry acquiring the mantle of the tobacco firms, who knew that the addictive nature of their product was good for profits but bad for public health.

Few believe the case against the food industry has reached that stage, but the evidence is accumulating.

And it may yet lead to an effective solution to the obesity epidemic emerging - not from the lab, but from the law courts.

Robert Matthews is visiting reader in science at Aston University, Birmingham, England