Delicious Drugs: How Processed Food Can Turn You Into An Addict

Can you actually become addicted to fast food? Sadly, new scientific research suggests the answer is "yes".

picture from Shutterstock

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.

Belinda Lennerz is a Fellow in Pediatric Endocrinology at Harvard University. She does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

The ConversationThis article was originally published at The Conversation. Read the original article.


    A "minority" are able to maintain a "normal" weight? Seems both statistically wrong, and a grammatical error.

      Indeed, maybe "healthy" should be used instead of "normal".

        Also... a minority are actually healthy weight? That's really horrifying.

        (Edit: But not bad for me. Less competition when the zombie apocalypse comes! I don't have to run fast. Just faster than the other guys.)

        Last edited 21/08/13 6:15 pm

    Glycaemic index is sort of an outdated measure and Insulin Index is gaining more traction.

    Fats in food slows the digestion and absorption of glucose into the blood. So, high fat foods like ice cream tend to have low GI.

    From the Uni of Syd GI database:

    premium high fat ice cream GI=37

    raw pineapple GI=66

    It seems like it was conducted with some degree of care. Have got to give them kudos for their bluntness of losing data on participants. They also controlled for a lot of factors which is good.

    The population they used were overweight or obese men. I would hazzard a guess that the effects are very different for underweight or normal weight people. They might get an interaction effect such that the high and low GI foods have the same effect on the cerebral blood flow for under and normal weight people, but where the high GI food has a massive effect on the bloodflow to the reward centres in obese people.

    That said, they didnt seem to have a baseline/control condition in the article. It is very very important to have a measurement that does not change between measurements so as to be able to attribute the changes to the GI of the food (rather than something else). What if for example they had a baseline and that it changes across the days in line with the cerebral blood flow to the regions of interest? In any sort of brain imaging (ASL included), having a good control condition is key (and also makes a massive difference in the activation that you see). Time of day would also be important (the resting state activity would probably fluctuate according to which meal has been eaten and is being anticipated)

    They should have done the study on obese drug addicts. Check the resting state activity before a mean on one day (baseline). Compare that to a low GI mean (on another day) and a high GI mean on a separate day and a shot of drugs on a different day (and yes, that would probably get past ethics boards...).

    (the original article)

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