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Transcript: Catherine L. Davis on Exercise Dose and Obesity in Children — DIC Interview

In this Exclusive Interview transcript, Catherine L. Davis  talks with Diabetes in Control Publisher Steve Freed during the ADA 2018 convention in Orlando about the surprising results of a study on exercise dose and obesity in children.

View the video interview on exercise dose and obesity here. 


Steve Freed:This is Steve Freed with Diabetes in Control and we’re here at the American Diabetes Association 78th Scientific Sessions, and there’s about 20,000 medical professionals and scientists here. And today we heve one of those people, a special guest who’s actually presenting here, and then maybe you can start off with telling us a little bit about yourself.

Catherine Davis: My name’s Catherine Davis and I go by Katie. I work at the Georgia Prevention Institute at the Medical College of Georgia, which is part of Augusta University in Augusta, Georgia. I am a clinical health psychologist and I do research in disease prevention and health promotion, particularly preventing diabetes and helping children to develop optimally.

Steve Freed: Can you tell us a little bit about your practice and what you do?

Catherine Davis: I am a researcher so I work to find out what it takes for overweight children to remain healthy and to have healthy development, and try to get that out to the folks out there that need to know.

Steve Freed: You’re doing a presentation and the title is “Youth Onset Type 2 Diabetes and Exercise Outcomes and Challenges.” So this is really about reporting on the results of your study. So why don’t we start out with asking you, what were some of the results?

Catherine Davis: Well that was the title of the session; my presentation is about “Exercise Dose and Diabetes Risk in Overweight and Obese Children: a Randomized Controlled Trial. So this is a report I made in 2012 in JAMA of a randomized trial of children who were overweight or obese, and most of them were obese, seven to 11 year old children, boys and girls. A slight majority Black, slight majority girls. And we randomized them to either a control group that got no intervention or one of two exercise groups. One of the groups got 20 minutes of vigorous physical activity a day in our research gym, and the other group got twice as much, so 40 minutes of the vigorous activity every day. And we were able to get good attendance. We were able to transport them thanks to the NIH support. And so it’s an efficacy study of what precisely happens when people do the exercise. So we got them to exercise by playing simple games with them, enjoyable. It was not physical education, we didn’t have a curriculum. The point was to get them to be more fit and more vigorously active. So we monitored their heart rates, and we incentivized their heart rates. So they would earn points depending on how high their heart rate was. The higher it was the more points they got. And so they really appreciated that because they would get little prizes, dollar store stuff, sparkly pencils and funny glasses and whatnot, every week for based on what their heart rates were. So the kids really enjoyed it. They were all able to do it. because these were also sedentary kids and so they were pretty out of shape. But even though a child may not be moving very fast that doesn’t mean their heart’s not going very fast. So through doing this we were able to also calibrate the intensity so that as they got more fit they did more work, because they have to expend more energy to get their heart rates up when they’re more fit.

Steve Freed: So let me ask you a quick question. Obviously we know exercise is good, especially preventing obesity, especially these children growing up, is a no brainer. So what were some of the surprises in your results that you weren’t expecting?

Catherine Davis: Well I really thought, I mean I was doing a dose response trial, I was trying to see if more is better, and I expected to find greater results in the 40 minute group than I did on the 20 minute group for things like insulin resistance. And I did not. It was actually the exact same effect in the 20 and 40 minute group, even though the 40 minute group was just as intense and burned twice as many calories as the 20 minute group. The effect on insulin resistance was the same. So I think what this means is that if you get at least 20 minutes of vigorous activity a day you will have a benefit on your insulin resistance. If you do more exercise than that, maybe 40 minutes a day, you’ll burn more fat, but the effect on insulin resistance and actually the effect on your fitness level will be the same. So I think it’s intensity that drives that benefit rather than energy expenditure.

Steve Freed: What were some of the measures that you’ve actually measured as far as A1c, BMI?

Catherine Davis: These were not diabetic children so we did not measure A1c. Our primary measure of diabetes risk was the insulin resistance. So we did an oral glucose tolerance test and used various methods derived from that to estimate insulin resistance occur according to how much insulin they secreted in response to a glucose load. And it turns out that fasting insulin is a far more reliable and really quite adequate measure to assess that response. So I would tell other researchers that using fasting insulin is really enough, because of course there’s more burden to the child and the lab to do your own glucose tolerance test. Nonetheless we wanted to do the best possible way we could so we did that. We also measured aerobic fitness with an exercise test. We measured fatness with whole body Dexascan. So a tiny amount of x ray that can assess how much fat is in your body as well as how much bone.

Steve Freed: What about dietary compensation. Does that play an important role?

Catherine Davis: It’s a possibility, but I found no evidence for dietary compensation. We did the best we could to measure children’s diets which is pretty challenging because it’s self report of course. However we did do detailed measures of diet at the beginning and the end of the study and assessed whether there was any change differential change between the groups and there was not.

Steve Freed: What about the effect on the brain and performance in school?

Catherine Davis: Well that was an ancillary study we did since we had the trial going and we were doing the intervention with all these kids, I thought you know, why not measure cognition — I’m a psychologist and I could do that kind of thing. And it turned out that surprised me as well; I was not expecting such clearcut results, but in fact the 20 minute group got a benefit and the 40 minute group got an even greater benefit on a measure of executive function, which is the kind of cognition that directs your goal directed activity. For instance if you need to study for a math test you should work on that rather than doing your social studies homework. Even though both are important, one of them is more important for that day. So we also looked at academic achievement, because I knew that if we were going to make a difference in policy we needed to show the educators what they cared about, and that’s test scores. So we got an achievement test that can be used to assess whether a child has learning disability for instance. And we did see a benefit but only in math. So we looked at math and reading as the two broad components of achievement and the kids in the highest dose exercise group got the highest benefit from the intervention on the math achievement, and there was a smaller benefit in the lower dose group.

Steve Freed: Has this work been translated translated into the communities?

Catherine Davis: It has started to be translated. We have more work to do but other researchers have done quite a bit of work about how to do exercise as part of school, during the school day and even perhaps as part of instruction. So there are movements where teachers are finding out that it’s actually helpful to keep their children focused, keeps their attention, keeps them alert I guess is what I’m trying to say. And so in Georgia we have a statewide program called Georgia Shape, and they got some money from Coca-Cola to go out to the schools and teach them how to have kids be physically active in the schools. And we’re actually monitoring the fitnessgram results for those kids. So it’s a standardized set of fitness tests and also a BMI measurement that is done on all the children every year, and our prevalence of obesity and our prevalence of better fitness has improved since this program rolled out. So that’s pretty exciting, statewide.

Steve Freed: How long was the study?

Catherine Davis: In the study, the children were in the intervention for about three months. The study took several years though to complete.

Steve Freed: So how did you get children to adhere to exercise for 20 minutes every day, because kids get bored real quick unless there’s a video game!

Catherine Davis: We kept them having fun. We motivated them with the prizes and the heart rate and we played really fun games with them. Mostly what the PE folks called Dodge and Flee games. So one of the best ones I liked was called Bumblebee Tag. And the teachers played with them. It was not teachers telling them what to do and standing there with a whistle. They were chasing them and engaging in the games. So with Bumblebee Tag there’d be one person with a pool noodle, and it might be my study manager in there in the gym with them, and whoever got stung with the pool noodle had to freeze and do jumping jacks. And then the rest of them are dodging, screaming, running around. So it’s good fun. It’s not a regulation sport. We weren’t interested in their skills. So there were basketballs and nets but nobody was counting who got points for scoring. It was only about their heart rate.

Steve Freed: So if you had to take a couple of things from your study that you would like to share with other medical professionals, obviously diabetes is a main factor, when it comes to diabetes in kids, most children are obese and very slow as far as exercise goes; they like video games and TV nowadays. What would you say to a medical professional that he can use to help his patients?

Catherine Davis: I would say if you can find an activity that the child enjoys, and this is advice to the parent of course, find an activity that the child enjoys that’s physical and encourage it. So it might be a Wi Fit videogame. I mean, you’ve got to start somewhere and I truly believe that a videogame is not going to get you as active as actually going outside or playing with others, but it’s a place to start. Go exercise with your child. Take a walk around the block, take your child to the pool, and try to make it a daily priority.


Steve Freed: What about walking the dog?


Catherine Davis: Walking a dog would be great, especially if it’s a young jumpy dog that wants to go fast!