A Rat’s Eye View of the Recent Junk-Food Study

June 2, 2010 in Blog Recipes, Diabetic Menu Item, Food and the Brain, Foodland, Psychology of Food, Weight Management, Whole Grains by Victor Bunderson

(As obtained from secret sources and adapted by guest blogger, Dr. Grandpa)

Editors note:  I sent a copy of a crucial new research study I found to Dr. Grandpa to write about.  It fit right in with his guest blog posts on how foods are designed to induce craving – even addiction.  The study is very complex to read and to explain. Dr. Grandpa worked at it for a while, then came back with the claim that two of the rats in the study were actually rats from The Secret of NIMH. For those of you who haven’t read the book or seen the Disney movie, some rats used in studies by the National Institute of Mental Health had been exposed to conditions that increased their intelligence so much that they could think like people and talk. At the time of this posting, Doctor Grandpa’s claims had not been verified. Nevertheless, since the rats’ story seems to correspond with the published study results, I decided to post this guest blog. Note: Dr. Grandpa really does have a doctorate from Princeton University in Psychology; so I feel very comfortable with him explaining studies that are about the brain and the psychology of eating. The subject of the study is serious, but the writing made me laugh out loud.

Doctor Grandpa:  It is fortunate that two NIMH-altered rats were assigned to be participant observers in a seminal experiment reported in the prestigious Nature Neuroscience journal. Authored by Dr. Paul Kenny and doctoral student Paul Thompson of the Scripps Institute, the experiment dealt with rats exposed to junk food constantly.  These rats became compulsive overeaters, became obese and sluggish, and their brains revealed evidence of changes similar to those found in human drug-addicts.  The conversations reported below were taken from three different days during the 54-day experiment.  The first conversation is from the 5-day point, where the two NIMH observer rats, Justin and Jimh, had just figured out that they had been assigned to the restricted junk food group.

Justin:  So the way I get it, there are three groups of us rats.  You and I are in the group that gets a go at that tasty human food.

Jimh:  Yeah, it’s great!  I tasted bacon, sausage, cheesecake, and something like DingDongs with tasty frosting and chocolate.  Trouble is, we only get our nibbles for one hour a day.

Justin:  Right, we can eat our regular rat-chow pellets at any time.  I guess they want to make sure we can get all the calories we need. But we are really limited on how much of the good stuff we get to eat. The pellets are ok, healthy stuff, you know (a rat-like smirk crosses his face), but that cafeteria food is really great!

(Doctor Grandpa aside:  Good health can be yummy.  It doesn’t have to be packaged and presented like rat pellets. Why don’t researcher’s ever do some studies with really palatable healthy alternatives?)


Justin: Over the past 5 days since the surgeries on our heads and the initial measurements they took, I’ve noticed that some other rats are getting different deals.  See the cages over there with the blue tags on them?  Those are the guys who don’t get any of the good stuff.  All they get is the same old rat chow every day.  Some kind of control group, I guess.  But take a look at the cages with the blue tags.  I counted 11 of those guys.

Jimh: Yeah, not a female rat in the whole study.  A bummer. But look at how much of the good food they get.  As fast as they eat it, the little metal food boxes are filled up again by the white-coated lab people.

Justin: Best I can make out is that the red-tag guys have the chow pellets available all the time, like we do, but they also have the good stuff available all the time.  We only get a short crack at it for one hour.  That’s not enough to fill us up for the day.  Good thing we have the chow pellets or we might starve.

Jimh: Yeah, the group with the red tag gets to eat the good stuff almost all the time, whenever they want.  I’ve noticed that after the first few days, they really cut back on eating their regular rat chow.

Justin: That’s an understatement! I’ve noticed that the blue-tag rats keep eating the tasty new food most of the time.  They have basically stopped eating the rat chow pellets. They just seem to hang out, eating.  Wonder why they don’t get full and quit?

Justin: (later) What are these scientists measuring?

Jimh: I notice that we get weighed once almost every day on the round metal scale.  So do the rats in the other two groups.

Justin: So they must be interested in how much weight we’re gaining on these three diets, the blue-tag guys who get no human food, just rat chow; our group, who gets one hour a day, and the red-tag guys, who get the human food anytime they want it.

Jimh: I can buy that.  Maybe the human food is fattening.  What I don’t understand is these things they glued onto our heads. After they knocked me out with the anesthetic, I woke up with a headache and there it was.  Once a day a feel some great little tickles in my head.

Justin: I feel the tickles too.  It’s feels soooo good!  It must be some kind of electrical current going into our brains someplace.  It’s like they start it out low, maybe too low to feel, then increase it until they see some kind of reaction from our brains, and it shows up on their instruments.  All I know is that at first I feel a tiny little tickle of pleasure, then it gets stronger and stronger.  Just when it’s really feeling great, they always quit. Let’s watch what they are doing when we feel the tickles next time.

Jimh: What I hate is when they shock our feet.  I try to get away from the food dish when the bell rings, before I get shocked. It hurts!  Do you think it is tied in with the tickle in the brain?

Justin: Don’t think so. It always comes after the bell sounds.  It goes on for some seconds before the shock hits us. If we hear the bell, we should get away from the food dish before the shock comes.

Jimh: Sometimes I hate this job working as undercover participant observers.  Having things stuck in your head is bad enough, (except it feels great when they give us the juice).   But getting shocked in the feet so you have to quit eating, especially during the short hour when we get to eat the good stuff.  That stinks.

Doctor Grandpa: This next conversation was heard on the 35th day. The smart rats, who can understand English, had been listening to the experimenters.

Jimh: So, Justin, what is your theory about the things stuck on our heads?

Justin: I watched them when they measured each rat in our group, and compared it with the other groups.  The measurements they do seem to go fast with the group that only gets the rat chow.  The experimenters don’t seem to need to keep increasing the level to get them to feel the tickle strongly.  With the group that gets the tasty food all day, it is different.  The experimenters seem to have to keep working with their instruments, apparently increasing the jolt they give over a longer period of time.  It seems like it takes more and more of a jolt to get the full-time junk food group to feel the tickle. Our group that gets the junk food only one hour a day seems to take only half as long as the all-day group to get the size of the jolt big enough so we can feel a good, solid tickle of pleasure.

Jimh: Hmm, we both overheard the lab guy, Johnson, talk about Dopamine Type 2.  He also abbreviates it to D2.  Is that what the tickle causes to be released in our brains?

Justin: Dopamine is a natural opiode given out by neurons in the pleasure center of the brain that makes us feel good.  So maybe the more any of us eat that tasty food, the less pleasure we feel from our own natural opiodes.

Jimh: I know you’ve seen their massively growing bodies.. Every one of the 11 is hugely obese. All they do is eat.  They used to run around and have fun. Now they just eat and overeat. What gets me most is what happens when the bell rings and the shock comes.

Justin: It’s hard to believe, isn’t it?

Jimh: You bet! I clear out when that bell rings.  That shock really hurts.  Those guys won’t move away from the food tray.  All they do is cringe a bit and lift up one foot, then another, as long as the shock is going.  They just won’t leave the food tray!


Justin: I overheard the older white-coat guy say that humans who are addicted to something he called “drugs like cocaine and heroin”, have the same things happen to their brains as happened to our sad, obese friends.  Drug addicts are compulsive.  They can’t stop going after the drugs.  They can’t stop taking them even when they suffer serious pain. Brains change when guys become obese too, and they don’t make enough D2 dopamine.  To feel any pleasure they compulsively overeat the tasty food.  The senior white coat thinks that this experiment gives the first really solid evidence that the same brain changes that take place when one is getting addicted to illegal drugs also take place when one gets addicted to overeating and becomes obese.

Jimh: Wow, so we are involved in some kind of landmark experiment!  Since we NIHM rats can see what’s happening here, I’m cutting back on the DingDongs and sausage next time we get a crack at it.  It took a long time for us few NIHM rats to get where we are, and I don’t want to blow it.

Justin: Me too.  Tough luck if it messes up their experiment.

Doctor Grandpa: Actually, it didn’t hurt the experiment noticeably.  On Figure 2 we do see that the restricted junk food group that Justin and Jimh were in had a slightly higher average of calories from Chow instead of junk food the last few days of the crucial first 40 days of the experiment.

The next conversation took place on the 50th day, 10 days into the 14-day period when the cafeteria-like food was withdrawn from both the limited group and the obese group.

Jimh: Man!  I make my big resolution to cut back on junk food and what happens?  They cut out our measly hour with it, to nothing.  It’s been 10 days without it now. I planned to cut back, not cut out!

Justin: Good thing we did cut back a few days before they cut it out.  We haven’t had such a hard time of it.  I really feel sorry for our fat friends across the way.  They haven’t been able to get back to eating their rat chow.  They hardly eat anything now.  Maybe they’ll lose a little of that flab before they either starve or learn to eat healthy food again.

Jimh: Poor guys.  They seem heartbroken and depressed to have lost their overeating life style with the tasty junk food.  I really hope they can learn to eat healthy food and be happy with it again.

Justin: If the first 40 days of the experiment are right, their brains were changed; their neurons don’t any longer generate enough dopamine 2 in their brains.

By the way, it’s almost time for us to use our special training and tools to unlock the cage, and get out of here.

Jimh: What’s the hurry, I heard this experiment goes another 4 days.

Justin: I heard the white coats talking about examining slices of the brains of some of the rats in each group under the microscope.  If we want to live to be participant observers in another experiment, we had better make our escape soon.

Jimh: Let me outta here, and fast.  I want the guys at central to take these things off of our heads, and a want a dish of our healthy but yummy NIMH rat food.

Doctor Grandpa: The two NIMH rats escaped successfully.  They both have that really up-to-the edge courage of movie heroes, and waited until after the last measurements were taken. The experiment was not compromised.  Their records have been transcribed and translated from rat talk into Grandma-appropriate talk (some of the more colorful rat language was left out).

I first cited this study in Part 2 of the Full or True Cost Accounting.  That post dealt with the design of foods for Craving.  This study is indeed a seminal study in the research needed to unravel the obesity epidemic.  For some of us, and those we love, this research gives us an understanding of what has happened to us.  The cafeteria food was available almost all the time, just like junk food in our personal environments.  When we eat it, we want more and more.  The reason is not just that we lack will power.  Addiction changes our brains, and is a very strong trap.

The reason it is so hard to overcome is that our brains change and make us more like people who naturally become addicts.  These people naturally have a gene that leaves them with less dopamine produced by their own brains.  To feel pleasure, they turn to drugs, sex, overeating, or other excesses.  Medical scientists have long suspected that obesity and drug addiction had a lot in common.  This study provides the strongest evidence yet that this is the case. It also shows that having hyperpalatable foods at hand all the time leads to compulsive overeating.  Compulsive overeating and the obesity it produces in turn leads to the brain changes that make it all the harder to resist.

In these blogs, Doctor Grandma is presenting some of the ways out of this trap.  A style of eating like the Mediterranean-style keeps us full and our blood sugar high enough so we do not feel the pangs so easily.  Cleaning up our environment so foods are not easily at hand helps enormously.  Building new brain pathways to bypass the addictive pathways is vital.  Exercise can help with that.

Here are some references for those of you who want to go deeper.

The obese rat study:  If you don’t have access to a library with a subscription to Nature Neuroscience, and can’t afford the $32 for the article, look at these other summaries:

From The NeuroScience reports of PhysOrg.com

From Scientific Blogging’s website:

Want the full explanation of addictive, hedonic foods from the man who lead the FDA and helped change the tide against cigarettes?

Kessler, James The End of Overeating

And, Doctor Neal Bernard’s explanation of addictive foods, and his advice on Breaking the Food Seduction


Wheat Berries, Tofu and Flavors of the Basque

This is my Wheat Berries and Flavors of the Basque recipe, with tofu instead of the fish. The lime really completes the flavor.


2 cups cooked wheat berries

14 oz. extra firm tofu, drained, cut into  ½ inch cubes

2 tablespoons extra virgin olive oil

1/8 teaspoon chili flakes

1 cup chopped onion

1 cup sliced mushrooms

14 ounces diced tomatoes, no salt added variety works fine

2 cups zucchini, diced

1 cup green bell pepper, sliced

1 cup red bell pepper, sliced

1 teaspoon paprika

1 teaspoon dried thyme leaves

1 teaspoon dried oregano leaves

1/8 teaspoon ground pepper

1/8 teaspoon salt, if desired

1 tablespoons orange zest

2 teaspoons garlic, minced

Slice of lemon or lime with each serving


If you have cooked frozen wheat berries, defrost; or cook 2 cups of wheat berries in 4 cups water for about 1 ¼ hour, until tender.

Infuse oil with chili flakes – about one minute.  Add onions and mushrooms and sauté until onions are clear – about 5 minutes. Add the tomatoes, zucchini, peppers, paprika, thyme, oregano, pepper, orange zest, and garlic – sauté until vegetables are tender and all ingredients are heated. Add the wheat berries and stir together. Serve topped with a slice of lemon or lime.

Beginning to add the second group of ingredients to the browned tofu, onions and mushrooms.

Beginning to add the second group of ingredients to the browned tofu, onions and mushrooms.

More flavor!

More flavor!

The last stir to blend the ingredients.

The last stir to blend the ingredients.

This was my dinner tonight.

This was my dinner tonight.