Link found between childhood obesity and slower thought processes

NIH funded study: healthy-weight children also better at correcting own errors

Listen to this podcast (MP3 - 9.8 MB).

Refer to caption.
Charles Hillman, Professor of Kinesiology University of Illinois' Division of Nutritional Sciences.

Barrett Whitener: A new study has found that extremely overweight or obese children are slower than healthy-weight children to recognize when they have made an error during an ongoing activity, and are slower to correct the error. The researchers studied the possible relation of obesity to "action monitoring," the ability to perform a task while simultaneously monitoring oneself to make sure things are going the way they're supposed to.

An example of action monitoring is when you're sitting at a computer typing, and without looking at your hands or at your screen you realize that you've made an error. Another example is of a child in school adding a column of numbers during math class. Action monitoring would be when she checks herself to make sure she remembered to carry the digit over from one column to the next.

The study found that healthy-weight children were better at action monitoring. The study authors say theirs is the first study to show that being overweight not only affects how quickly children react to what they've seen, or when something happens, but also that being overweight can affect how well a child's brain organizes, plans, and prioritizes thoughts.

The brain processes involved in action monitoring are necessary to succeed in skills such as math and reading, so they're linked to success in school and in life generally.

From the National Institutes of Health, I'm Barrett Whitener. This is "Research Developments," a podcast from the NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development, the NICHD. Joining me today is Charles Hillman, one of the study's authors. Dr. Hillman is Professor of Kinesiology and a faculty member in the University of Illinois' Division of Nutritional Sciences. Thank you for joining us today, Dr. Hillman.

Charles Hillman: Thank you.

Mr. Whitener: Before we get started, can we talk a little bit more about action monitoring? It's kind of a tricky concept. I wonder, is it like when someone is driving a car and they stay on course by maintaining a constant speed and control of the steering wheel, that kind of thing?

Dr. Hillman: Yes, that's exactly right. This is a subset of behaviors that are involved in monitoring our own actions. I know that's using the words that are in the name, but it's the idea that we have a system in place whose job it is to check that our actions are correct. Some of the examples you used in your introduction were spot-on in terms of—an example I always use to discuss action monitoring is that we often don't need to look at our computer monitor when we know we've made a keystroke error. And that's because our action monitoring system is in place and is checking to make sure that our behaviors and our responses are matching what's appropriate in the environment around us.

Mr. Whitener: Let's talk for a minute about earlier research. Have any other studies found a connection between healthy weight and academic achievement?

Dr. Hillman: There are some studies out there. This field is in its beginning stages. At the very onset, I think I should probably make it known that we don't know the direction of these relationships. It's entirely possible that having better cognitive functioning or better executive functioning is related to healthy weight, as opposed to maybe unhealthy weight relating to poorer cognitive function. We don't know the direction that it goes. There is data that exists from my lab and from others that demonstrates relationship between body mass or, you know, healthy versus unhealthy weight status with academic topics such as reading, spelling, and arithmetic.

Mr. Whitener: What led you to decide to focus on this particular area of cognitive control, action monitoring?

Dr. Hillman: Well, my lab is interested in different types of cognition and, in particular, we're interested in aspects of cognition called executive functioning or cognitive control or executive control. And these aspects of cognition are mediated, in part, by the prefrontal cortex. And action monitoring falls within this class of cognition and is also mediated by part of the prefrontal cortex.

And so, on the one hand, we're interested in this class of cognitive functions. And, on the other hand, my laboratory is focused on markers of health or markers of health behaviors, of which proper or healthy body weight would be included. Other behaviors that we talk about in the laboratory are physical activity and proper diet and nutrition or hydration status, as well as markers of health such as aerobic fitness or, in some cases, obesity or metabolic syndrome.

Mr. Whitener: How did you measure the children's action monitoring ability?

Dr. Hillman: We measured action monitoring using a standard test that we've been using in our laboratory for quite some time called a Flanker test. This test is a test of inhibition. That is, the children look at an array of fish that are swimming in one direction or the other, left or right, and they press a button based on the direction in which the target fish or the middle fish is swimming. So, when that fish faces to the right, they press a right button; when the fish faces left, they press a left button. Later on, we make the task more difficult by asking children to respond with the opposite hand. So, if the fish swims left, they press a button with their right hand.

Having said that, the actual—when it comes to action monitoring, the actual task itself doesn't matter all that much, because what we're interested in is looking at the response that children have when they make an error. And errors can be made using any number of different tests. And so we look at differences between correct responses and incorrect responses, regardless of what type of test was used.

Mr. Whitener: And how did the overweight children differ from the healthy-weight children in terms of how they performed that task you just described?

Dr. Hillman: Yes. So on the Flanker task, healthy-weight children differed from obese children in a number of different ways.

First, obese children performed more slowly than healthy-weight children so that when they saw that fish and they identified the target, the time it took for them to press a button in response to that target was slower than healthy-weight children. We saw this effect in the easier conditions, but we also saw the effect was larger in the more difficult conditions.

Secondly, we looked at the responses after they made an error. And so, when an individual makes an error, on the very next trial they oftentimes will assume a more conservative response set, meaning that they slow down, they ensure accuracy, and it's normal for an individual upon making an error to really try not make a second error. And what we found was that obese children performed more poorly on the trial following an error, as opposed to healthy-weight children. Again, we saw this effect in the easier condition and we saw the effect was even larger when the condition was more difficult.

Mr. Whitener: Now, I know you've also looked at the electrical activity in the brains of the children in the study. Please tell us some about that. What were you trying to find out by looking at that activity?

Dr. Hillman: Yes. So, studying the neuroelectric system of the brain, as well as other imaging measures, is a nice way of gaining an understanding of some of the underlying processes that occur between when an individual first sees a stimulus and when they formulate a response. And so, while reaction time and other behavioral measures are very valuable, they basically just provide us with the end result. And so, being able to look at the electrical processing that occurs within the brain allows us to get at aspects of cognition that we wouldn't necessarily be able to make inferences about from just the reaction time or accuracy data.

And so, what we found in this case was a potential called the error-related negativity or ERN. This potential in the brain grows larger when individuals make an error. And so, healthy individuals have a large error-related negativity when they make an error as opposed to when they make a correct response. And it's thought that this potential is a reflection of the evaluation that an error has occurred. And so, as I mentioned before, when individuals are performing a task, they oftentimes have a system that is checking their responses. In this particular case, the checking system, or the ERN is a reflection of this checking system, so they have evaluated that an error has occurred.

What we found relative to body mass in children was that obese individuals had—obese kids had a smaller ERN compared to healthy-weight children, suggesting that their error monitoring system or their action monitoring system isn't as well—or isn't as effective as the healthy-weight children.

We saw this effect during error trials, but not during the correct trials, suggesting that there's some selectivity in their ability to execute or efficiently execute this potential during a speeded task. And what we see is that this effect occurred primarily in the easier condition. And so what that means is that, during the easier condition when an error was made, healthy-weight children had a large ERN response. Obese children had a small ERN response.

When the task became more difficult, what we saw was that healthy-weight children modulated their response downward, where obese children stayed the same. And so the differences were seen when it was easy, but not necessarily when it was difficult. And actually we would have expected this.

There is data from our laboratory on another topic, which looked at aerobic fitness and its relationship with the error-related negativity potential. And what we found was that higher-fit individuals were better able to modulate their ERN response, so as the number—the amount of resources involved in that response was titrated or matched that of the cognitive task or the difficulty of that cognitive task.

And again here, what we see is that healthy-weight children are better able to modulate their response, modulate those resources in response to the demands of the task, where obese children are not able to up-regulate or increase that ERN response and it remains fairly stable, smaller and stable, across the various conditions.

Mr. Whitener: You mentioned earlier that you're not quite sure at this point what direction the research will be going or what direction it points us in. But for the benefit of any parents and caregivers listening, I wondered if you could discuss any possible implications of your study for those folks who are listening to us.

Dr. Hillman: Well, I think the implications of this work are that for a long time now, we've known that there is an obesity epidemic that is upon us and, no pun intended, is potentially growing. We're aware that obesity has implications for various health parameters: organs and tissue and bone.

But our understanding of the relationship between obesity and brain health is only in the very beginning. There's only maybe, you know I'm estimating, about 10 papers in the literature, and of those, only a very small handful come—or are on the topic of kids and obesity. And so we're really at the very beginnings of our understanding. And I think this paper is one of the first to demonstrate that being obese has implications not just for physical health but also brain health, and that tasks such as these are indicators of potential deficits in cognitive function that may occur in relation to being obese.

Mr. Whitener: So the familiar advice about make sure your children are getting enough exercise, eating healthy foods, etc., sounds like it may have implications that we hadn't even known before.

Dr. Hillman: I think that's correct, yes. There is a number of different organizations, you know, from the American Heart Association to CDC to the Institute of Medicine, that have all created recommendations for child physical activity behaviors and how much physical activity they should receive on a daily basis. And one thing is clear: that the children in the United States and other Western cultures have not—do not engage in the recommended amount of physical activity on a daily basis. And those implications are, you know, are the issues that we're fighting today, and probably there are several other implications that we're unaware of at this time.

Mr. Whitener: Well, thank you so much for speaking with us today, Dr. Hillman.

Dr. Hillman: Thank you.

Mr. Whitener: I've been speaking with Dr. Charles Hillman, co-author of the study, "The Negative Association of Childhood Obesity to Cognitive Control of Action Monitoring," which was published in the journal, Cerebral Cortex.


About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute's website at

top of pageBACK TO TOP