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Food addiction: how processed food makes you eat more

Most people have the strong desire for a normal weight but in many developed countries such as Australia, only a minority are able to achieve it. Research we recently published provides an insight into…

We don’t just eat for fuel. Doug DuCap/Flickr

Most people have the strong desire for a normal weight but in many developed countries such as Australia, only a minority are able to achieve it. Research we recently published provides an insight into why.

In theory, weight reduction is as simple as cutting down on the number of calories consumed. But most people continue to overeat, driven by constant temptation.

While many argue that maintaining a healthy weight is an individual responsibility, the widespread availability of tasty but highly-processed food provides a temptation to overeat that many simply cannot resist.

Addicted to food?

This inability to resist gave us the idea of testing whether certain types of food can lead to “addiction”.

While some experts argue we can’t be addicted to food because eating is essential for life, people eat for many reasons unrelated to their daily energy requirements. Many eat out of stress, for instance, or frustration or for pleasure.

We wanted to know whether these eating behaviours are perpetuated by highly-processed, tasty food, especially those with a high glycaemic index. High glycaemic index foods include refined starches and concentrated sugar and cause a rapid rise and fall in blood sugar after consumption.

Typically, blood sugar falls below fasting level within a few hours of a high glycaemic index meal, causing hunger and leading to overeating.

Conversely, foods with a low glycaemic index, such as whole fruit, vegetables, legumes and minimally-processed grain, produce relatively little blood sugar fluctuation, and longer satiation.

Our research

We aimed to understand how highly-processed carbohydrates can cause such a strong surge to overeat. Is it just a matter of blood sugar levels? Or does the supreme tastiness of highly-processed foods play a role?

In order to answer these questions, we created two milkshakes, one with a high, and one with a low glycaemic index. The milkshakes were otherwise identical, with similar calories, macronutrients and taste.

We gave the milkshakes to 12 healthy, overweight men on different days and in random order. Four hours after the high glycaemic index shake, participants were hungrier than those who had consumed the low glycaemic index shake.

We also did functional MRI imaging on all 12 participants. The images revealed intense activation of the nucleus accumbens, a critical brain area in the dopaminergic, mesolimbic system that mediates pleasure eating, reward and craving.

Similar activation patterns have been found in people after consumption of addictive substances, such as heroin and cocaine.

What it all means

Our findings provide qualified support for the possibility of food addiction.

While food is necessary for life, we eat for reasons beyond our daily energy needs. When overeating becomes a pattern that is hard to break, we say someone is “addicted” to food.

Previous studies looking at food addiction have compared brain activation in response to palatable foods and linked addictive behaviours to the pleasure and reward that people experience after eating them.

But those studies typically compare grossly different foods, such as cheesecake versus vegetables, and raise the possibility of confounding. This means the addictive pattern may be caused by any number of food properties, such as appearance or taste, a subject’s preference for certain foods, or the number of calories consumed.

Our study controlled for confounding dietary factors and suggests that the glycaemic index can independently affect hunger and overeating. More research is needed to examine the relevance of the idea of food addiction and the treatment of eating disorders and obesity.

But the fact that a food property may affect addiction centres in the brain, independent of calories or pleasure, provides the basis to rethink current dietary recommendations.

Obesity is one of the hardest conditions to treat as dietary restrictions often cannot be maintained in the long term. Any help a person can get in maintaining a healthy energy balance is valuable. This line of research may inform novel and individualised approaches to a healthy weight.

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12 Comments sorted by

  1. George Michaelson


    There is addiction, and there is habituation. I can understand some dictionary fanatics arguing addiction isn't going to be a good fit, although I think the physiological changes which come from eating specific forms of food might get you over the line: there is an adjustment in the body's physiology?

    But Habituation.. I'm there.

  2. Kelvin Wright

    Parent, employee, student etc

    The question is do the corporations that create these foods already know this?

    1. R. Ambrose Raven


      In reply to Kelvin Wright

      Of course they know. Addiction is the ultimate aim of any profit-seeker. It guarantees sales. That's why Big Tobacco tries to get the kids to smoke, just as the AHA./ Big Alcohol tries to get them to drink.

  3. Deirdre Alderton

    Retired Health Worker

    This topic is gaining in interest. There have been some good programs on the radio (have a look at last week's Health report) and SBS (recent Michael Mosely series) that have elucidated this apetite stimulating mechanism more fully. Apparently Atkins was ahead of his time!

  4. Neville Mattick
    Neville Mattick is a Friend of The Conversation.

    Grazier: ALP Member at A 4th Generation Grazing Station

    Great article thank you.

    Addiction; I am addicted to organic Rolled Oats, as though they are going out of fashion, at least once a day / 365 and twice to thrice in Winter.

    Professor Robert Lustig is interesting too on the role of Fructose, Leptin and how it // they lead to excess.

    Interestingly, I have a habit of overly liking Honey and of late far too many fresh apples from our orchard, alas I have to cut these down to once per week or else Fructose mal-absorption sets in with a few side effects too.

    Most processed foods make me sick fairly quickly, especially the symptoms from Fructose.

  5. R. Ambrose Raven


    Naturally, whatever amounts of money seem necessary will be spent by Big Obesity to convince our politicians and the voting public of the evils of another tax, in this case on unhealthy (“fast”) food. As a Parliamentary researcher noted, “to date, the Australian response to this issue has emphasised the value of a self regulatory regime. However, this approach may be modified in the future, as a result of a number of factors. These include growing public demand for intervention and a shift in health…

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  6. Gary Cassidy

    Monash University

    Although this type of research is interesting and useful, under our current food/economic systems it will only be used to replace one set of low quality food with another set of low quality low GI food. I fear with minimal differentiation in health outcomes.
    "foods ..... such as whole fruit, vegetables, legumes and minimally-processed grain, produce relatively little blood sugar fluctuation, and longer satiation"
    Notice how this statement doesn't require "with a low glycaemic index" (replaced with dots). It just is.

  7. rory robertson

    logged in via email

    Dr Lennerz,

    Thanks for your discussion. I agree that food addiction is a major problem, and it seems that added sugar is a key driver of many such addictions. Here's Dr Eric Clapton on sugar and addiction:

    My sense is that low-GI diets can be worse-than-useless if they include super-low-GI-19 added fructose, the "sweet poison" half of added sugar. After all, added sugar - including in sugary drinks - is a key driver of global obesity and diabetes…

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  8. Alfred Nassim

    logged in via LinkedIn

    A little background. I am 63 and have had a BMI of 21.5 - almost unchanging - for 40+ years. My 3 kids (8, 12 and 22) are similar to me. My wife of 14 years was overweight when we married and she now has a BMI of 20. I have a pair of trousers that I bought in Germany 25 years ago which still fit me perfectly.

    I think people, especially physicians and researchers, are keen to know what obese people are doing that is different. There seems to be very little research into the behaviour of people…

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  9. Jamie Hayes

    Managing Director at Healthy Inspirations

    We need to be cautious not to accept statements like "In theory, weight reduction is as simple as cutting down on the number of calories consumed." as this alone is being hotly debated.
    It is worth reading Salt Sugar Fat: How the Food Giants Hooked Us Hardcover
    by Michael Moss.
    I suspect that sugar and salt are addictive but fat is not.
    I also suspect that the reason we see overweight and obese parents and grand parents buying their kids a "treat" at the local fast food, is that the parents are addicted and are using the kids as an excuse. Pity the poor poisoned children.

  10. margot cullen


    its never ending is it...the experience i have witnessed in real time is ....why not a psych approach for the obesity. e.g i have seen xxx friends ., family., pts., undergo xxx attempts at modifying diet and exercise and then surgery out of frustration but what keeps putting stuff in their mouth...does not matter whether it is low or high G index?...they just keep shovelling it in....look more closely at their mental health rather than just food, exercise, adverts and so on.we dont hesitate to use the mental health diag of anorexia nervosa for the opposite in extreme cases.

  11. Abu Noman M Atahar Ali

    PhD Candidate at School of Law, University of Wollongong

    I wonder, is there any study that endeavors to change brain's activation to the ''palatable foods' ?