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 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 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.

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  1. 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.

    Er, if they can produce a low-glycemic milkshake with the same taste, why isn’t this on the market? The only thing I can think is that they made two awful-tasting milkshakes, one slightly less bad for you than the other.

  2. I think this could be summarised as in our evolution, sodium salt and calories were hard to come by. When we came across them, especially in concentrated form, we gorged. Modern packaged food manufacturers optimise salt, sugar and fat levels for maximum appeal (regardless of health). This lets them sell some very cheap crap at inflated prices. Every prepared product in the supermarket has added salt and sugar, optimised for flavour, even products you would never think would contain these ingredients.

    In nature potassium is relatively easy to get. In processed food it is rare. In nature, unless you are at the seaside, sodium is hard to get. In processed foods it is hard to get away from.

  3. In reply to #2 by DallasDad:

    if they can produce a low-glycemic milkshake with the same taste, why isn’t this on the market?

    The high glycemic foods are very cheap to produce. They are often crammed with starch, which is very very inexpensive.

  4. In reply to #2 by DallasDad:

    Er, if they can produce a low-glycemic milkshake with the same taste, why isn’t this on the market?

    I’ll admit I don’t know, but have had similar questions myself in the past. For example, if we can make crisps$ taste like anything delicious (e.g. Walkers has run at least one “we’ll invent the best-sounding suggested crisp flavour” contest), why haven’t we applied the same technology to make healthy foods taste better? I’d eat a lot more fruit & veg if they tasted like meats. My guess is that, because a crisp is a low-mass, high-surface-area, flat object, you an easily overpower any flavour it might have alone with a thin layer of chemicals. However, I know they’ve made “crisps” out of healthier things, so I’m sure we’re not doing all we could with this technology.

    $ Potato chips, to Americans.

  5. It’s a complex situation:

    The world class experts in creating these highly palatable products are employed by the major industry players, mostly tobacco companies. (Or soon will be if they create anything that approaches significant market share.) Distribution and marketing constraints tend to favour more uniform products, so niche products which aren’t as highly addictive and so generate lower profits don’t tend to be allowed to continue. It’s a variant of Says Law: bad processed food drives out good.

    And international globalisation factors mean that there is no room in the market for anything other than world class expertise. (And lowest possible costs of production.) There’s a double whammy in that combinations of stable fats, sugar, and salt making up fake foods are highly addictive as well as tasting and feeling fantastic, while also greatly minimising production, transport, storage, and distribution costs – compared to actual food.

    On the other hand there’s possibly a reduced carbon footprint compared to real food – which has much high costs of production. Plus real food doesn’t help as much with diminishing human population growth and increasing rates of disease and therefore potentially mitigating global environmental degradation. Similar to the economic advantages of encouraging older retired pensioners to smoke cigarettes. It’s possibly no coincidence that the relevant manufacturers tend to be related.

    The ubiquitous availability of processed foods when treating overweight, obesity, and NCDs is like attempting to treat gambling addiction while the player is still in the casino with bets in play. A related analogy being that relevant treatment guidelines are developed according to research funded by the casino operators’ industry association. It’s also possible that encouraging cigarette smoking and consuming processed foods may even assist with overcoming gambling addiction. But substantial research on this may need to wait until more casino operators invest in tobacco and food processing enterprises.

    In reply to #2 by DallasDad:

    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.

    Er, if they can produce a low-glycemic milkshake with the same taste, why isn’t this on the m…

  6. A good insight into the problem is Jacques Perretti’s BBC documentary “The Men Who Made Us Fat”.

    Over 3 episodes it covers such topics as the insidious insertion of high fructose corn syrup into prepackaged food to compensate for the trend for low fat, the inception of supersizing and giving unhealthy food a superficial “Health halo” to dupe unsuspecting dieters into parting with their cash whilst doing nothing for their waistlines.
    Well worth a watch if you have access to iPlayer.

    Episode 1 is especially relevant here. The bottom line is if you’re expecting food lobbyists to set their house in order and sell us healthier products, don’t hold your breath.
    They all seem to be reading from the Nick Naylor playbook

  7. I think there is also an important component in fast food addiction that is rarely (if not never) discussed: the incessant visual onslaught of billboard and television ads, especially the latter. Whenever I watch any TV series or sport events on US network TV, the amount of fast food ads is staggering. The food is lighted and filmed in a way that makes it looks irresistible: it’s food porn. And it’s really bad.

    TV watchers in the US (children in particular) are constantly bombarded by these ads. Burgers, fries, wings, pizza, fried chicken, pasta, shrimp, ribs, more fries, steak, hot-dogs, soft drinks, gatorade, etc. etc. Over and Over and over again. Within a mere hour of TV watching, a few hundred pounds of food will have been paraded before your eyes.

    You’re not hungry? Just ate? No problem, we’ll make you hungry again, garanteed.

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