What television can tell us about childhood obesity

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Research Profile - March 2008

Dr. Harvey Anderson may have found the perfect combination to engage teenage boys - free, all-you-can-eat pizza and their own televisions to watch the Simpsons while eating.

Anderson is not running a teen social club out of his office at the University of Toronto. Rather, he's been pursuing some small experimental studies to understand more about the problem of childhood obesity. One of Anderson's conclusions is that eating while watching television overrides our ability to know when to stop eating; in effect, mindless television watching produces mindless eating.

A specialist in nutrition, Anderson, like others in his field, has been alarmed by the rising rates of childhood obesity. He wants to help address the problem by studying that which makes us feel full, so-called satiety factors. In the past year, he's published several papers on the subject to attempt to explain how these factors work in children.

Certain well-known hormones such as Leptin have already been fingered as being among the culprits, a kind of blame it on your genes, reason for the inability to control appetite.

But, given the high rates of childhood obesity, Anderson is not convinced that genes provide the whole story. To understand the bigger picture, he's been looking at other factors such as one's environment (where one lives, daily routine, and so on) that, together with genes, are likely to provide a more balanced, realistic explanation of what's going on. "Our food intake control system is actually very good and is not in disarray despite what one hears about the obesity epidemic," he says.

So, Anderson decided to take a closer look at how television affects eating.

"It was the first study done of its kind. People have looked at the influence of television before, but only in terms of how much television was watched during the day, not whether kids were eating while watching television and how much they ate."

When kids showed up at Anderson's office, 2 hours after breakfast at home, half of the group was given calorie-free sweetened water, while the other received sweetened water with glucose, a so-called caloric pre-load. Lunch was served 30 minutes later. Of these two groups, some ate while watching the Simpsons, while the others ate without the television on. Over the course of the experiment, the kids came back four times, each time being exposed to a different condition.

The kids who received an extra calorie bump prior to the meal and did not watch TV during the meal ate the least. But, among TV watchers, the extra calories seemed to have not effect on how much they ate. Overall, the kids who watched TV consumed an average of 228 extra calories at lunch. While this may not seem like much, the effect of such extra calories on a regular basis adds up. Based on his results, Anderson has some immediate advice for parents - turn the television off during mealtime.

With support from CIHR, Anderson, along with then PhD candidate Dr. Nick Bellissimo, has pursued other related research on satiety factors among children.

Another recent study looked at how well glucose and whey protein drinks suppressed appetite among obese and normal weight boys. It is well known that, at least among adults, proteins suppress appetite more strongly than glucose, but Anderson notes that the study produced "profoundly puzzling" results. For example, there was little reduction in appetite among obese boys who received the protein drink compared to normal weight boys. "So, why was this? It could be that body fat is having some effect on the protein. It could be that body fat is holding back or impeding the protein from helping suppress the appetite," he speculates.

Anderson remains committed to studying the issue further, particularly to help ease the challenges overweight children face in losing weight. "I'm concerned about overweight kids and how they respond to a diet at a time when their body is driving them to eat to support growth."