All of us have had the experience of knowing that we’re not hungry, that we’re in fact full, but going ahead and eating anyway. In my experience, this usually happens when I have the opportunity to eat something unusually yummy. I typically don’t overeat my broccoli or salad. So this is what lunch looked like chez Freberg last Saturday….
Alain Dagher and his colleagues might have an answer for this [1]. They remind us that eating is both homeostatic (maintaining a constant supply of nutrients) and hedonic, or pleasureable. Homeostasis is likely driven by hormonal effects on the hypothalamus, whereas the hedonic effects are due to the activity of reward areas.
One of the hormones involved with appetite is ghrelin, manufactured in the lining of the stomach and in the pancreas. Dagher and his colleagues gave volunteers an intravenous dose of ghrelin while they underwent functional MRI. When the participants looked at pictures of tasty food, like pizza, those who had received ghrelin showed increased responses in areas associated with the anticipation of a payoff. In other words, when ghrelin is present, we view food as more rewarding, and the resulting brain activity is similar to the activity of the brain in addiction.
How can we apply this new knowledge? Pharmaceutical companies are definitely looking at manipulating ghrelin to reduce appetite, but the side effects could be dreadful. If ghrelin has a more general effect on reward and incentive in addition to boosting appetite, blocking that general effect could lead to depression. In addition, we need to figure out why obese people already have low levels of ghrelin and people with anorexia have high levels of ghrelin [2].
1. Malik, S., McGlone, F., Bedrossian, D., & Dagher, A. (2008). Ghrelin modulates brain activity in areas that control appetitive behavior. Cell Metabolism, 7(5), 400-409.
2. Dostálová, I., & Haluzík, M(2008). The role of ghrelin in the regulation of food intake in patients with obesity and anorexia nervosa. Physiological Research [epub ahead of print.]
11 Comments
bwerter · May 10, 2008 at 1:11 pm
I feel I eat much more when I am bored, or when there is a lot of food around. Recently I made way too much pesto (like half a gallon, it was two batches in a 10 cup food processor) so I have been eating way too much of everything I can possibly think of putting pesto on to be sure to eat it before it goes bad. It seems like there is a huge variety of factors influencing our eating habits and that changing one thing will not affect them in the proper way. The ultimate diet pill will probably involve many neurotransmitters.
l.ogden · May 10, 2008 at 7:10 pm
The title of this article immediately caught my eye, considering I just finished eating when I wasn’t really hungry. This article was able to inform me of some relevant things I didn’t know. I often eat for hedonic reasons; I love to prepare and eat good food. I never attributed this desire to hormonal reasons. The correlations between ghrelin, anorexia, and obesity are very interesting. Even though manipulations of the level of ghrelin could help decrease eating motivations, I don’t think that this is something that should be too tampered with. I don’t have much will power, but if I needed to for my health I would be able to work on it. There are more reasons that obesity is a problem in America than just hormones. I just don’t agree with the idea of adapting the body without previous personal effort put into the situation. I am wary of fueling a lazy America.
jmgraham · May 11, 2008 at 1:02 pm
I feel trouble coming! While discoveries of things like ghrelin are fascinating, I fear their impact on society. Especially in such an appearance driven society, the potential of abuse of these drugs is all too predictable. Coming from a family who struggles with eating disorders, I can already hear the elation at the mention of an appetite reducer.
What I found most interesting in this article is the measures of ghrelin in those with obesity and anorexia. If ghrelin makes us view food as more rewarding, I would automatically think that the obese would have high doses of it, and those suffering from anorexia, low levels. To me, the data that proves opposite displays that these disorders are psychological. It’s not about obese people wanting more food and anorexic people not wanting it. Obese people get less reward, and so probably eat more to fulfill that satisfaction or they may eat out of habituation. Anorexic people, though they don’t eat, still want to eat! Or at least their brains. And maybe because they have starved themselves, their brains are kicking in and increasing ghrelin to say, “look at how good that food looks! eat it please!” I think that the study of ghrelin should be taken further and then diagnosed and protected with so much caution so as to not get America hooked on another weight loss supplement.
Laura Freberg · May 11, 2008 at 5:00 pm
Great comments, Everyone!
I thought the obesity and anorexia results were interesting, too. In following up, it appears that the authors assume that the ghrelin and leptin systems are trying to adjust to the imbalance of weight, but that’s just a hypothesis. Obviously, we need more research on this.
AprilN · May 11, 2008 at 8:23 pm
I have noticed that I seem to eat mainly because I am bored. I think that if there was a pill to reduce appetite, people would have to work on changing their habits first.. like me. I don’t think that a pill would help prevent someone who’s bored from eating.. mainly because it’s something to do. I
I also found those obesity and anorexia results interesting as well. More research is definitly needed.
svallier · May 12, 2008 at 5:57 pm
I found this topic, and the various different threads of responses on this topic too interesting not to contribute. First of all I find food incredibly rewarding, so I’m guessing my ghrelin levels are functioning just fine. I also agree on the part of eating when I’m bored, so going off of what AprilN was saying, isn’t finding a pill that makes you feel full rather than merely reducing your appetite a smart plan for those pharmaceutical companies? This would mean there would be no need to block the ghrelin, and your reward/ incentive system wouldn’t be thrown for a loop. I’m sure there are many out there that do just what I’m talking about, I’m just making a point that this line of research would probably be safer!
KCCHAFFEE · May 12, 2008 at 8:03 pm
I too identify with the other comments, I often eat when I am bored. Unlike Mrs. Freberg, I tend to overeat when the food I am eating is not satisfying. If I am having a good meal I eat it and am happy, but if it is not very good I will continue to eat it, but also snack after the meal is over, I suppose because I am still looking for a certian taste or satisfaction. Although I do overeat, and would love to loose a few pounds, I would not consider taking a pill to help me stop overindulging. Unless you medically have an imbalance in ghrelin, or have severe weight problems, I think that loosing weight the old fashion way is best. I know, I know, eaiser said than done.
kara311 · May 12, 2008 at 8:47 pm
I did some research on Ghrelin and found an interesting article (http://www.sciencedaily.com/releases/2006/05/060510091429.htm) that suggests Ghrelin may be a treatment for Diabetes. In trying to further the hypothesis that Ghrelin promotes obesity, Dr. Roy G. Smith bred mice to be deficient in Gherlin. These mice were just as fat (supporting the null hyposthesis) but they had lower levels of glucose. Either way, everything is still way too experimental for the pharmaceutical companies to start claiming they have the next cure for obesity or diabetes.
knphilli · May 13, 2008 at 11:21 pm
I also eat a lot when Im bored, but I find that I eat the most when Im not hungry if I am upset, depressedd, or tired. I usually crave snack-like foods. I looked for some reasearch on if Ghrelin levels increased with depression or not but I couldnt find anything. Do you know if they are related?
itsmuoi4 · May 30, 2008 at 12:32 pm
I guess I’m the odd one out. When I’m bored I actually feel LESS hungry and tend to shy away from food. When I’m in an upbeat mood or feeling positive, I eat out of enjoyment even though I’m not hungry. Weird? I don’t know, maybe subconsciously I’m looking something to liven up my mood. Anyways, learning about ghrelin is quite interesting, especially because I do indeed believe that some people need something to control the overeating especially with overweight Americans. Sure it would lead to abuse and what not, but the rate of obesity going up also means the rate of other health problems including cancer rising. Eating can almost be compared to an addiction for some and helping restore the imbalance of ghrelin would greatly help decrease in their chance of health complications and what not. Of course, it would only be beneficial if it would use only for that purpose but when does that ever happen when dealing with drugs?
shakiamitchell · March 12, 2009 at 9:33 pm
Wow!! I definitely have had times in which i’ve eaten more than I really needed to, typically at buffets or the holidays. It never occured to me that there was an actual chemical that produces the urge to want to overeat I thought it was purely psychological going back to that ol saying ” your eyes are bigger than your stomach”. It’s interesting to know there is a biological reason behind this. The obesiy and aneorexia info was interesting, it would be great if ghrelin could help these people with their eating disorders.
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