MR. KOJO NNAMDIWelcome back with the reminder that there's a tornado warning in effect until 1:00 pm for Arlington County, Prince George's County, Eastern Fairfax County and Washington, D.C. until 1:00 pm. A tornado warning is more dangerous than a tornado watch, so you'll want to make sure you take appropriate precautions. More than 30 percent of American children are overweight or obese.

MR. KOJO NNAMDIAnd while doctors have always known that high sugar, high fat diets have long-term impacts on health through heart disease, diabetes and cancer, little has been known about the impact of unhealthy diets on the body's third largest organ, the brain. Today, a growing number of scientific research is uncovering surprising impacts from childhood to adulthood to old age. But junk food may actually rewire young brains deteriorate memory functions and impulse control.

MR. KOJO NNAMDIAnd that childhood and adolescent diet could even contribute to long-term adult illnesses like dementia and even Alzheimer's. We're joined by two researchers who studied the link between diet and the brain from childhood to adulthood. Terry Davidson is director of the Center for Behavioral Neuroscience at American University where he is also a professor a psychology. Terry Davidson, thank you for joining us.

MR. TERRY DAVIDSONYes.

NNAMDIChantal Nederkoorn is a professor of psychology and neuroscience at Maastricht University. Her research has focused on the psychology of eating and impulse control. Chantal Nederkoorn, thank you for joining us.

MS. CHANTAL NEDERKOORNYou're welcome.

NNAMDIYou too can join the conversation with your questions or comments. Call us at 800-433-8850. When we talk about food that is high in sugars, high in fat, many of these products have been highly engineered by food companies, their recipes have been explicitly refined to stimulate taste receptors of young people, they're marketed in such a way that they stimulate our other senses with bright boxes, catchy commercials. So kids are being bombarded with temptations in many ways that we don't always fully recognize, right?

DAVIDSONYes. Matter of fact, the term is called the obesogenic environment. And the idea is that all these cues and these very highly palatable foods, the fact that we see all the advertising and so on kind of overwhelms our ability of our bodies to control our intake. And so we have a kind of a natural regulatory system and that system isn't doing very well in the face of all this environmental onslaught.

NNAMDIWhen we talk about long-term affliction like heart disease, most of us can intuitively understand that our diet can impact the physical functioning of our body. But we don't tend to think about the brain as an organ in the same way that we think about the heart or liver and we don't really think about our diet impacting how our physical brain works. What is the link between diet and the brain? Terry?

DAVIDSONSo it is a case that we've kind of had a neck-down approach to obesity in terms of the diseases that it produces. Most recent data suggests that, well, I guess midlife obesity has been associated with Alzheimer's disease in late life. And what we've been very interested in is trying to figure out when this kind of deterioration begins. And what seems to be happening, at least some of the work that we've been doing and others have been doing is you're actually getting a breakdown of the brain's protections.

DAVIDSONThe brain is protected by what's called the blood-brain barrier. And diets that are high in fat, high in sugar seem to weaken that blood-brain barrier. When that happens, things can get into the brain that don't normally get in and they may not only affect cognition or ability to remember and think, but they also may affect our ability to refrain from eating foods or refrain from responding to those food cues in the environment, which may make us eat more.

NNAMDIThe brain is an incredibly complex organ and it turns out that certain types of diet can have positive or negative effects on the functioning of different quadrants of the brain. Some of your research has focused on the hippocampus. Is that how it's pronounced?

DAVIDSONThat's correct, yes.

NNAMDIWhich controls learning and memory. How does diet impact its function?

DAVIDSONSo we just had a symposium on this topic. And our own data says that what happens is you can get inflammation. So inflammation is usually a sign of disease or some kind of insult. The hippocampus will show signs of inflammation in animals and people that have been on these diets. Also, there's evidence from MRI studies in children in adolescents that the actual size of the hippocampus shrinks. And so, it looks like you're getting some kind of atrophy. And that was one of the findings that was supported yesterday at the symposium.

NNAMDIChantal, we often talk about junk food as having this physical pull on us. For example, it's very hard for many if not most people to eat just one Dorito chip. It's hard for some people to look at a box of donuts and not take one of them. You have studied impulse control in kids and adults. What do we know about why some people really can't seem to resist eating unhealthy foods?

NEDERKOORNI think for most people it's difficult, as you say, if you see really palatable food or you smell it, most people already respond to it physically. It might be that you already feel some salivation in your mouth if you really smell tasty food. However, as you say, some people are more vulnerable for that. So not only do they react more physiologically, but they also have more difficulties to inhibit their response. So if you are more impulsive, environmental cues are more important for you. You react more to them.

NNAMDI800-433-8850 is our number. Do you see a link between diet and memory and other cognitive functions? Give us a call, 800-433-8850. If there is indeed a scientific link between unhealthy and childhood diets and long-term diseases, should we begin to rethink our food policies? 800-433-8850. You can send email to kojo@wamu.org. Shoot us a tweet @kojoshow or join us at our website, kojoshow.org where you can ask a question or make a comment there.

NNAMDIChantal, I should have also addressed the question that I earlier addressed to Terry about the way things are marketed, the way they stimulate our senses with bright boxes, catchy commercials and in many ways we don't fully recognize. How important is that?

NEDERKOORNThat's very important. I think if you are really impulsive and you live in a, well, let's say in America 100 years ago, you wouldn't have any problems resisting food because simply it wasn't out there in the it's out there now. So it's really important that in -- yeah, it's the main effect of the obese -- increase of obesity so the environment cause. However, we also know that not everyone is as vulnerable to the environment. So there are individual differences, how well you can cope with our environment.

NNAMDITerry, more than five million Americans have Alzheimer's disease, a disease that tends to affect people in the latter stages of their lives and can have devastating impacts on families. What do we know about the link between diet and Alzheimer's?

DAVIDSONSo it looks like there's a link where the incidents can go up from -- well, if you have a hundred people of normal weight with Alzheimer's disease, you might see as many as 170 people or all the way up to 230 that have high body adiposity or high body fat in midlife. It looks like even if you lose a little bit of weight, after that period of time, you still have an increased risk. So there's a link between this diet and obesity with Alzheimer's disease.

DAVIDSONThe basic brain pathologies in those folks that may progress to Alzheimer's disease but -- exactly the real etiology, what is actually going on in the brain is the subject of a lot of research right now.

NNAMDIOn to the telephones. We'll start with Derek in Fairfax, Va. Derek, you're on the air, go ahead please.

DEREKI want to say hello to "The Kojo Nnamdi" family there.

NNAMDIThank you.

DEREKI'm enjoying this show. I just want to bear witness to what your guests are saying. I had high blood pressure, my kidneys was bad, the liver was bad, bad cholesterol, the whole nine yard. And obviously my diet was under the floor. And I changed that by including good fats, good fiber and good protein, eating a large amount of plant-based foods that I juice. And basically every six months, I get a lab report from my doctor. And I've turned everything around. I actually feel better, unbelievably better than what I did before that.

NNAMDIAnd I think both Terry and Chantal, what he is saying we have heard before, what's different now is what we are learning about the effect of diet on the brain and how that effect starting in childhood can continue until adulthood and even old age.

DAVIDSONSo that's the issue is that it -- there's already evidence that children are showing cognitive deficits. And it doesn't take a longtime, say, in research models or animal models for these deficits and even some of the pathologies to start showing up in these areas of the brain that are responsible for learning and memory. Yeah, I think that's the -- what's new about it. And the fact that it's happening in children is even -- is even more frightening.

NNAMDII should mention that the National Weather Service has now canceled the tornado warning for D.C. A severe storm warning, however, remains in effect. Allow me to repeat, the National Weather Service has canceled that tornado warning for D.C. A severe storm warning remains in effect. What does this new research mean? Does it point to any kinds of interventions, either to rewire the brain or to deal with the effects? Is the solution here going to be cognitive therapy or some sort of drug treatment regimen?

NEDERKOORNI think the most important treatment still aims at reducing the intake of high fat, high sugar and increasing physical activity. I think that's still the most important thing to do.

NNAMDIWe won't necessarily see interventions here?

DAVIDSONSo one of the problems is, as your caller indicated, we know for the long time that if we eat right and get more exercise, we'll have a healthier life. The problem is how to get people to do that. And we actually think that the changes in the brain we're seeing preventing people from doing that. So the targets that you might...

NNAMDIAnd those changes in the brain begin at a very early age is what...

DAVIDSONSo that's -- what we're seeing is changes in hippocampus and other brain structures -- so the brain is a complicated place. It's not like an amorphous piece of Jell-O that or a bunch of neurons, it has a lot of different kids of structures in it. And a lot those structures are involved with decision making and controlling, inhibiting our behaviors. Those are the ones that seem to be affected by this disease.

DAVIDSONIn terms of interventions, I'd mention that blood-brain barrier is breaking down. I'm not sure that's happened in kids. I know it happens in animals, I know it happens in older folks. But one thing to do is if we can find out this happens in kids is it might be easier for us to do an intervention early. Quite frankly, dementia -- all the dementias are very difficult. In other words, once those symptoms are full blown -- and quite often we don't even diagnose it until it's too late.

DAVIDSONIf we can identify these markers either memory functions in terms of cognitive functions or some kind of changes in physiology of the brain early on, the techniques we have for treatment might be much more effective.

NNAMDIOn again to the telephones. Here now is Mike in Alexandria, Va. Mike, your turn.

MIKEHey, Steve, Kojo. I -- I know that this is a lot of research that's sort of confirming what people have understood for a while that there's certainly a link between this type of food and brain development or lack thereof. But I'm wondering if there's anything about using the power of marketing since that seems to be such a driving factor in getting people hooked on these poor foods, how to use that power or some sort of manipulation to get people hooked on the right kind of foods.

MIKEFor example, at a young age, my mom would put food in front of me and she'd say whether -- I'd say what is this? And she'd say it's asparagus, you like it. Oh, okay, I already like it, then I would just eat it. And now I've been eating it my whole life.

NNAMDIChantal?

NEDERKOORNThat's a terrific example. And indeed strategies that can be used to learn to like fruit and vegetables more. And I know that there are some tricks that we use to sell unhealthy food that can also be used to healthy foods. So that's an excellent idea and it should be used more often.

NNAMDISuch as persuading your kid that already likes something that he didn't know he already like. But apparently it worked in Mike's case. Thank you so much. But it brings us to the issue again of childhood because here in the United States there's been a renewed focus in recent years on school lunches, especially for lower income kids who may rely on meals at schools for the bulk of their healthy food.

NNAMDITeachers have long observed that kids who are hungry tend to misbehave in class. This research would seem to underscore how important these programs could be.

DAVIDSONYes. I think it's actually the case. In fact, at the symposium yesterday, some researchers from A.U., Stacey Snelling and Sarah Irvine Belson, they actually do studies of school lunch programs and D.C. is very progressive in that they have a healthy D.C. where they're trying to put fresh fruits and vegetables into the school lunches. One of the problems that was apparent yesterday is that a lot of kids still won't eat them.

DAVIDSONAnd so you can put them on the plate, but a lot of it is being wasted. And so, there has to be some other way that maybe the idea of how do we get them to like them better? There were some people who talked a bit about that, too, how do you get kids to like asparagus? How do you get them to like green vegetables and so on? It's not an easy thing to do, but there are ways that it might be accomplished.

NNAMDIChantal, does the brain respond to this kind of training, if you will, from an early age if it is trained, if it is taught to appreciate healthy foods? Does that simply continue into adulthood and old age?

NEDERKOORNYeah, I think so. There are many studies that show that if you are -- if you like a variety of food and vegetables early in life that you also like and eat more fruit and vegetables later in life. So there's definitely a relationship how well you do as a child and how well you will do as an adult.

NNAMDIFinally, here is Diana in Potomac, Md. Diana, you're on the air, go ahead please.

DIANAHi, Kojo, thank you. I want to quote Michael Pollan, the author and cook and nutritionist. He said, "Eat food, not too much, mostly plants." And the second thing I wanted to say is that I hope that this discussion can be extended at some point by you, regarding how really sugar and at least in this country there's a whole lot of sugar being consumed by young children and adults in the form of alcohol. And I wonder how that's working in such a...

NNAMDIWell, we're almost out of time here. Adult -- alcohol is mostly consumed by adults, but a lot of sugar by children.

DAVIDSONThere's a lot of carbohydrate in alcohol. What we've seen sugar itself -- so if you had a really high sugar diet, you're going to produce all kinds of problems in terms of diabetes and -- diabetes itself like type 2 diabetes can produce long-term effects. But it seems that we're most at risk when we have the combination of high saturated fats and high sugars.

NNAMDITerry Davidson is director of the Center for Behavioral Neuroscience at American University, where he's also a professor of psychology. Chantal Nederkoorn is a professor of psychology and neuroscience at Maastricht University. Her research is focused on the psychology of eating and impulse control. Chantal, thank you for joining us. And, Terry, thank you for joining us.

DAVIDSONThank you.

NNAMDIThank you all for listening. I'm Kojo Nnamdi.