These and other heavily processed foods with a high glycaemic index (GI) trigger an addictive sugar rush that can be hard to resist and leads to obesity.

New Zealand scientists reviewed evidence showing compulsive food consumption has similar underlying brain mechanisms that result in drug dependence, and argue that heavily processed carbohydrates have the most potential to cause addiction.

Lead researcher Simon Thornley, from Auckland Regional Public Health Service, said foods with a high GI caused blood-sugar levels to spike suddenly, and this sugar rush stimulates the same areas of the brain associated with addiction to nicotine and other drugs. Low-GI foods produce gradual rises in blood sugar and insulin levels, and a feeling of contentment and satiety.He said the theory, if proven, had important public health implications.

Nicole Wigan from Maroubra said she makes sure her two children eat a balanced diet, but her son, Jack, 4, "could eat junk food all day long if I let him".

Having a school holiday treat of fish and chips at La Perouse beach yesterday, Ms Wigan said while she's heard of the glycaemic index, she doesn't do the weekly grocery shop based on high- or low-GI foods.

"I don't pay attention to it, but generally we eat quite a balanced diet and if they've eaten well, they can have a treat at night," she said.

This is the first time GI has been implicated as the predictor of the addictive potential of foods.

Dr Thornley said evidence showed people who binged on high-carb foods experienced symptoms of addiction - loss of control, a compulsion to keep taking higher amounts to get the same buzz - and suffered withdrawal if they went cold turkey.

And like those addicted to cocaine and alcohol, people with a higher body mass index had fewer brain pleasure receptors.

Carb addicts may benefit from getting their hit of blood sugar more slowly by eating low-GI foods or even using a food version of the nicotine patch. "Just as slow release forms of nicotine help smokers recover from addiction, low GI foods may reduce cravings in obese or overweight populations," Dr Thornley and his colleagues at the University of Auckland wrote in the journal Medical Hypotheses .

GI pioneer Jennie Brand-Miller, from the University of Sydney, welcomed the study but said the assertion high-GI foods have a shorter time to peak concentration in the bloodstream is incorrect. All foods take about 30 minutes to peak, but high-GI foods peak and fall at substantially greater levels, Professor Brand-Miller said. "It's a novel idea that draws on strong evidence that glucose consumption influences levels of the feel-good chemical serotonin in the brain."

An editorial in The American Journal of Psychiatry last year proposed some forms of obesity are driven by an excessive motivation for food and should be classified as a mental disorder, or "food addiction" in the upcoming Diagnostic and Statistical Manual of Mental Disorders .

The director of the US National Institute on Drug Abuse, Nora Volkow, wrote that the symptoms of obesity - compulsive consumption of food and inability to restrain from eating - are remarkably parallel to those described for drug dependence.

The professor of population health at Deakin University, Boyd Swinburn, said while there were commonalities between drug-seeking behaviour and the extreme measures a starving person will go to for food, labelling obesity an addiction was "far-fetched".