Friday, March 7, 2008


During the 1940s and 50s, an Austrian psychologist named Konrad Lorenz studied the behavioral patterns of geese.

One of the things he observed was the egg-retrieving behavior of the greylag goose. When an egg rolls out of a goose's nest, it gently uses its bill to roll it back in. However, when Lorenz took an egg from the nest and placed it next to a larger round white object, the goose preferentially rolled the larger object back into its nest while ignoring the real egg. He called this larger object a superstimulus. It was an abnormally strong stimulus that was able to hijack the bird's normal behavioral pattern in a maladaptive way.

Our brains are wired to respond to the stimuli with which they evolved. For example, our natural taste preferences tell us that fruit is good. But what happens when we concentrate that sugar tenfold? We get a superstimulus. Our brains are not designed to process that amount of stimulation constructively, and it often leads to a loss of control over the will, or addiction.

It's a very similar process to drug addiction. Addictive drugs are able to plug directly into the brain's pleasure centers, stimulating them beyond their usual bounds. Food superstimuli do this less directly, by working through the body's taste reward pathways. In fact, sweet liquids are so addictive, rats prefer them to intravenous cocaine. You can't take just one hit of crack, and you can't have just one Hershey's kiss.

Our bodies are finely honed to seek out healthy food, but only in the context of what we knew when our tastes developed during evolution. If all that's available is grass-fed meat, pastured eggs, vegetables, fruit, and nuts, your appetite will naturally guide you to a healthy diet.

If you surround yourself with superstimuli such as sugars, refined grains and MSG, your body will not guide you to a healthy diet. It will take you straight into a nutritional rut because it's not adapted to dealing with unnatural foods.

Your brain is pretty simple in some ways. It has these very basic hard-wired associations, like "sweet is good" and "free glutamate is good". If your brain likes a little bit of sweet, then it really likes a lot of sweet. If it likes a little bit of glutamate from meat, then it really likes a flood of glutamate from MSG. Just like the graylag goose that prefers the big white ball over her own egg, your brain drives you to ignore normal stimuli in favor of more potent superstimuli.

This explains the partially true saying "Everything that tastes good is bad for you". Why would your body deliberately encourage you to damage your health? In our hunter-gatherer state, it didn't. In this age of processed food, our technology has outstripped our ability to adapt.


Anna said...

Excellent post, Stephen. The book, Sugar Blues, by William Duffy, has some illuminating history on sugar. Sugar has quite a fascinating history - it fueled empires, slavery, and trade. Historical accounts of peoples' response to sugar sound like addictions to drugs, which is probably hard to imagine in the present, but perhaps that's only because sugars are so commonplace now. Most people I know couldn't imagine giving up all concentrated sugars, even with the use of artificial sweeteners.

Stephan Guyenet said...

Interesting. Sugar is so ingrained in our lives. So are cavities and chronic diseases...

Ross said...

Hi Stephan, interesting idea that makes a lot of sense in explaining our sugar habits. But what about foods that taste good and are good for us - like tea, cloves, ginger, blueberries, or dark chocolate? How do we know whether a food tastes good because it's a superstimuli, or because it simply is beneficial to our health and we've evolved a taste for it?

Also (on a less nutrition-related note) I'd be cautious about interpreting the study where rats could self administer for either cocaine or saccharin. Was the preference for saccharin lever because of more craving for sweetness, or because the rats learned to associate that lever with reward more easily? It takes some time for the cocaine to kick in before the rat feels a "buzz", and a rat may have difficulty associating that reward with some action it performed 10, 30, 60 (?) seconds ago. Rats that only got cocaine never achieved the same lever-pressing ability as rats that only got saccharin (fig 1b). And in rats that got both, the apparent preference for the saccharin lever declined with increasing delay between lever press and saccharin delivery (fig 4c).

Stephan Guyenet said...

Hey Ross,

Welcome to the blog. Those are good points. I had a feeling I'd learn something new if you commented on this post. I still think it's remarkable that sweetness can compete with cocaine at all, given how addictive cocaine is in rats even with a delay between stimulus and reward.

About how to know what's a superstimulus and what's not, I think a general rule is to stay within the types of things we might have encountered as hunter-gatherers. That doesn't mean we can't eat vegetables or spices that were unknown 15,000 years ago, it just means we should stay in the same categories.

Any taste that's extraordinarily concentrated by some industrial process, relative to what we could have foraged, should be seen with suspicion in my opinion.

For example, we have sugar and glutamate ("umami") receptors on our tongues. Any food that hits those receptors with an unnaturally concentrated stimulus is going to be a potential superstimulus.

Of course, you could say honey is an exception, since some groups would have had access to it. But wild honey is not common anywhere in the world, and it's nonexistent in many places. You'd have to be really (un)lucky to get your hands on enough wild honey on a regular basis to hurt your metabolism.

Peter said...

Hi Stephan,

That goes some way to explaining the rat/sweetness/cocaine paper. I still find it amazing that the phenomenon is so potent. Having read Mark Johnson's autobiography Wasted I find it more amazing still. Mind you, Johnson gave up drugs because he got hold of an essentially unlimited supply of crack and heroin and just iv-ed the mixture until it not only failed to do anything in terms of high, it didn't even blunt withdrawl. Modern man on sugar?


Stephan Guyenet said...

Hi Peter, glad to see you on the blog!

I'm also amazed at how addictive sugar can be in animals. Perhaps the reason we don't think of it in those terms in humans is we're just too familiar with it. Most people eat plenty of sugar every day, even though many of them know it makes them feel bad.

Anonymous said...


I’ve been reading your blog for a couple months and am enjoying your recent series on reward. After reading part III, I reread part I where you introduce the food reward concept and ended up on this post.

In part I, you make the case that our brains make judgements about everything and that the superstimuli of processed foods can throw all of that out of whack. And here you say that if all that’s available is grass-fed meat, pastured eggs, vegetables, fruit, and nuts, our appetites will correct themselves (with the caveat that if surrounded by superstimuli, we’ll end up with an unhealthy diet).

Do you have thoughts about how mass media introduces visual stimuli (and sometimes hooks into other senses like smell and sound) for superstimulus foods and how that might complicate the natural correction of our appetites?

It seems impossible to not surround yourself with superstimuli, even if our pantries are perfectly paleo. How to break the appetite’s preference of ever-suggestive sugars, refined grains, MSG that we’ve all been rewarded for at some point in our lives? Can rats read billboards?

Super interesting stuff. Thank you for writing.