Junk food could be addictive 'like heroin'

Rats became 'hooked' on sausage and cheesecake in same way as drug abusers

Junk food may be addictive in the same way as heroin or cocaine, according to a study showing that laboratory rats will endure painful electric shocks to satisfy their craving for high-calorie snacks made from sausages, bacon and cheesecake.

Scientists have found that a "café-style" diet of fatty, sugary food results in compulsive overeating among rats and causes neuro-chemical changes to the brain that mimic the sort of alterations in the human brain brought about by addiction to heroin and cocaine.

The findings lend support to the idea that certain types of energy-intensive foods can trigger compulsive overeating and obesity in humans, leading to a form of food addiction that is almost impossible to overcome by dieting.

The researchers found that rats offered junk food quickly became so attached to it that they would endure painful but harmless electric shocks to their feet in order to eat it. They would even prefer to starve themselves rather than eat the "salad bar option" of the typical rodent food eaten by rats that had never had junk food.

When the scientists analysed the brains of the junk-food rats they found that a key pleasure-reward system known to be involved in triggering drug addiction in humans was overstimulated, causing the animals to eat more and more food in order to enjoy the same chemical "high" felt in their brains.

"It presents the most thorough and compelling evidence that drug addiction and obesity are based on the same underlying neurobiological mechanisms," said Professor Paul Kenny at the Scripps Research Institute in Jupiter, Florida.

"The animals completely lost control over their eating behaviour, the primary hallmark of addiction. They continued to overeat even when they anticipated receiving electric shocks, highlighting just how motivated they were to consume the palatable food."

The three-year study, published in the journal Nature Neuroscience, tried to reproduce a diet for rats based on the sort of high-calorie, high-fat food known to contribute to human obesity. The scientists found that it was easy to accustom the rats to eating such delicacies as sausages and cheesecake.

"They always went for the worst types of food and, as a result, they took in twice the calories as the control rats. When we removed the junk food and tried to put them on a nutritious diet – what we call the 'salad bar option' – they simply refused to eat," Professor Kenny said.

"The change in their diet was so great that they basically starved themselves for two weeks after they were cut off from their junk food."

Rats showing an addiction-like behaviour towards junk food also had fewer dopamine D2 receptors in a part of the brain called the striatum compared to ordinary rats. These receptors are responsible for triggering a response to dopamine, a neurochemical that transmits signals between certain brain cells involved in the feeling of pleasure towards things like food, sex and drugs.

Fewer D2 receptors in the striatum of the human brain are associated with drug addiction, as well as a genetic predisposition towards obesity. In the case of the rats, they compensated for the fall in receptors by eating more junk food in order to stimulate the less-sensitive pleasure-reward pathway in the brain, Professor Kenny said.

"It was the animals that showed the 'crash' in brain reward circuitries that had the most profound shift in food preference to the palatable, unhealthy diet. These same rats were also those that kept on eating even when they anticipated being shocked," he said.

"When the animal overstimulates its brain pleasure centres with highly palatable food, the systems adapt by decreasing their activity. However, now the animal requires constant stimulation from palatable food to avoid entering a persistent state of negative reward.

Professor Kenny added: "These findings confirm what we and many others have suspected, that overconsumption of highly pleasurable food triggers addiction-like neuroadaptive responses in brain reward circuitries, driving the development of compulsive eating."

When normal rats had their dopamine D2 receptors thinned out by a virus, they immediately showed the same kind of addiction-like behaviour seen in rats given junk food. "Common mechanisms may therefore underlie obesity and drug addiction. [It is] as far as we know the strongest support for the idea that overeating palatable food can become habitual in the same manner and through the same mechanisms as consumption of drugs of abuse," Professor Kenny said.

Suggested Topics
Life and Style
ebookNow available in paperback
ebooks
ebookA delicious collection of 50 meaty main courses
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
SPONSORED FEATURES

ES Rentals

    Independent Dating
    and  

    By clicking 'Search' you
    are agreeing to our
    Terms of Use.

    iJobs Job Widget
    iJobs General

    SThree: Trainee Recruitment Consultant - Bristol

    £18000 - £23000 per annum + Uncapped OTE: SThree: SThree Trainee Recruitment C...

    Recruitment Genius: Purchasing Administrator - Chinese Speaking

    £17000 - £24000 per annum: Recruitment Genius: This rapidly growing company is...

    Recruitment Genius: Start a Career as a Financial Markets Trader

    £40000 - £100000 per annum: Recruitment Genius: Become a professional Trader a...

    Recruitment Genius: Software Implementation Consultant

    £45000 - £50000 per annum: Recruitment Genius: This software company specialis...

    Day In a Page

    Giants Club: After wholesale butchery of Idi Amin's regime, Uganda’s giants flourish once again

    Uganda's giants are flourishing once again

    After the wholesale butchery of Idi Amin's regime, elephant populations are finally recovering
    The London: After 350 years, the riddle of Britain's exploding fleet is finally solved

    After 350 years, the riddle of Britain's exploding fleet is finally solved

    Archaeologists will recover a crucial item from the wreck of the London which could help shed more light on what happened in the vessel's final seconds
    Airbus has patented a jet that could fly from London to New York in one hour

    Airbus has patented a jet that could fly from London to New York in one hour

    The invention involves turbojets and ramjets - a type of jet engine - and a rocket motor
    10 best sun creams for kids

    10 best sun creams for kids

    Protect delicate and sensitive skin with products specially formulated for little ones
    Tate Sensorium: New exhibition at Tate Britain invites art lovers to taste, smell and hear art

    Tate Sensorium

    New exhibition at Tate Britain invites art lovers to taste, smell and hear art
    Ashes 2015: Nice guy Steven Finn is making up for lost time – and quickly

    Nice guy Finn is making up for lost time – and quickly

    He was man-of-the-match in the third Test following his recall to the England side
    Ashes 2015: Remember Ashton Agar? The No 11 that nearly toppled England

    Remember Ashton Agar?

    The No 11 that nearly toppled England
    Turkey-Kurdish conflict: Obama's deal with Ankara is a betrayal of Syrian Kurds and may not even weaken Isis

    US betrayal of old ally brings limited reward

    Since the accord, the Turks have only waged war on Kurds while no US bomber has used Incirlik airbase, says Patrick Cockburn
    VIPs gather for opening of second Suez Canal - but doubts linger over security

    'A gift from Egypt to the rest of the world'

    VIPs gather for opening of second Suez Canal - but is it really needed?
    Jeremy Corbyn dresses abysmally. That's a great thing because it's genuine

    Jeremy Corbyn dresses abysmally. That's a great thing because it's genuine

    Fashion editor, Alexander Fury, applauds a man who clearly has more important things on his mind
    The male menopause and intimations of mortality

    Aches, pains and an inkling of mortality

    So the male menopause is real, they say, but what would the Victorians, 'old' at 30, think of that, asks DJ Taylor
    Man Booker Prize 2015: Anna Smaill - How can I possibly be on the list with these writers I have idolised?

    'How can I possibly be on the list with these writers I have idolised?'

    Man Booker Prize nominee Anna Smaill on the rise of Kiwi lit
    Bettany Hughes interview: The historian on how Socrates would have solved Greece's problems

    Bettany Hughes interview

    The historian on how Socrates would have solved Greece's problems
    Art of the state: Pyongyang propaganda posters to be exhibited in China

    Art of the state

    Pyongyang propaganda posters to be exhibited in China
    Mildreds and Vanilla Black have given vegetarian food a makeover in new cookbooks

    Vegetarian food gets a makeover

    Long-time vegetarian Holly Williams tries to recreate some of the inventive recipes in Mildreds and Vanilla Black's new cookbooks