Thursday, April 19, 2012

A Pavlovian approach to the problem of obesity

To whom it may concern.  This is my personal blog, created for the dissemination of thoughts and analysis of various research papers over an eight week span.  Every week I will be analyzing one or several papers on the general idea of learning as it deals with eating behaviors.  I will attempt to focus on issues dealing with obesity/uncontrolled-eating, etc. but as I research these topics, I may drift from this topic and write about whatever interests me under the general umbrella of learning and eating.  I want to thank Professor Blaisdell, who is my honors contract advisor and teacher of Psychology 110 at UCLA for proposing the idea of writing in a weekly blog.  It is a fascinating concept that I am undertaking as an experimental project for these next eight weeks, while keeping an open mind of the possibility of writing beyond that time span.
       And now to get to the real issue at hand, I will be giving my feedback on an article I came across on google scholar known as "A Pavlovian approach to the problem of obesity".  Article 1 on obesity.  I recommend reading the article first before continuing on.
       I believe that the problem of over-eating stemming from associated learning of sweet-tasting food and high calories is an interesting take, but one that should be tested on humans, now that some evidence has arisen in rats.  The test these experimenters conducted was to make two groups, one consistent with sweet-taste and high calories, and the other an inconsistent association, with sweet-taste but lower calories (non-caloric saccharin was used). Once these connections were trained and established for ten days, the rats ate lab-chow for one whole day, then starved overnight so that they would be hungry for the next day of testing. After the overnight starvation, the rats were all offered a sweet tasting high-calorie chocolate pre-meal, followed by lab chow for 1 hour.  What the experimenters are hoping to see here is a difference in controlling caloric intake between the consistent and inconsistent groups because the rats in the 'consistent' group made an association between sweet food and high calories.  The experiments showed that the consistent group rats consumed less of the lab chow in the 1 hour after the pre-meal in order to compensate for that heavy caloric intake.  The rats in the 'inconsistent' group ate a considerably greater quantity of the lab chow after the pre-meal than the rats in the 'consistent' group.  This is an interesting finding because it is seen so readily in our every day life.  We see people taking in a variety of foods such as candies that are very-sweet and high calories, but also foods that are sweet but low in calories like diet-coke, vitamin-water zero, some breakfast bars (nutrigrain bars) or something like sweet potatoes.  This creates an 'inconsistent' association between sweetness and calories that may cause people to underestimate how many calories they are actually taking in while eating sweet and sugary foods.  As a result of the breakdown of the predictive relationships between sweetness and calories, people begin to over-indulge in sweet foods such as cakes, ice creams, etc.  People may not regulate how much they take in of the sweet foods just as the 'inconsistent' rats in the experiment did not regulate how much of the lab chow they ate, because they did not think they had taken in so many calories with the pre-meal.
         The second experiment aimed to see if similar restrictions are made when rats are tricked into thinking they are taking in a low-calorie, low-viscosity drink which actually had the same calories and nutritional value as a high-viscosity substance.  The association has been made that low-viscosity drinks are relatively low in calories, while high-viscosity ones are high in calories, stemming from time spent breastfeeding.  Rats in one group that drank the low-viscosity drink (made this way by adding water) ended up drinking more and gaining more weight than the rats who drank highly viscous drinks (made this way by adding nonmetabolizable guar) showing that they could not regulate the calories they took in, as they had done with the sweet foods.  The problem I see with this experiment that the researchers did not adress is the ease with which we consume low-viscous foods compared to high-viscous ones.  Talking from personal experience, I would definitely prefer to drink multiple cups of chocolate milk because of convenience and speed, compared to eating (or trying to gulp down) multiple cups of chocolate pudding which takes longer to enjoy and can be more effortful.  The association in my mind is not as clear between viscosity and calories, and the reason behind my choice is one of convenience, speed, and simply a preference, which are not adressed in this paper.  As wikipedia defines viscosity: "Put simply, the less viscous the fluid is, the greater its ease of movement (fluidity)"... I prefer to consume foods that flow easily into my mouth, rather than wait for something like honey to flow out slowly. However, If the findings of this study are found to be true in a test with human experiments, it is clear to see the reasons why.  Once again, this can be seen in every day situations where people have lost that connection between viscosity and calories, because of the plethora of foods which we consume, some of which have been artificially modulated to adjust for calories or viscosity.  Something like Coca-Cola is not very viscous, but contains many calories and disrupts that learned association that people may have from breastfeeding.
     In conclusion, I just wanted to say a few words about societal overeating habits.  I have personally dealt with issues of overeating throughout my life and I want to say that all people have different preferences for different tastes and foods, usually overlooking the need to balance caloric intake.  Despite having an association with calories and certain types of food, there are so many factors at play when eating food that may have gone overlooked in this study.  Until this can be replicated in trials with hundreds of human participants, I will take the results with a grain of salt.  I can see strong support in every day life for the issues that the researchers were getting at, while there is more convincing evidence here for the sweetness/caloric association disruption than the viscosity.
    In any event this is just a rough first trial at keeping a blog, as I hope to polish up my writing from week to week and possibly give more elaborate analyses as we study these topics further in class and as I look at more research articles.  Thank you for reading.

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