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TV Viewing and Childhood Obesity – Less Related Than Expected?

Never mind that it is usually impossible to infer causality from observational studies or, even if significant associations are noted, to predict what may or may not happen, when one of the variables is targeted (as in an intervention). It is also worth noting that many common stereotypic assumptions we make about what may or may not be driving the obesity epidemic continue to be challenged by the actual data on these issues.

A good example of this state of affairs is the recent paper by Valerie Carson (a former CON Bootcamper) and Ian Janssen (an enthusiastic Bootcamp faculty member), from Queens University, Kingston, Ontario, published in Pediatric Obesity on the relationship between TV viewing, snacking, and childhood obesity.

While we are all familiar with the ‘stereotypical’ pictures of the fat kid with a bowl of chips with eyes glued to the TV set, suggesting that fat kids are fat because they do little else than watch TV and eating chips (forgetting that skinny kids may do exactly the same), this paper certainly does not easily support this notion.

The study looked at the self-reported snacking and TV viewing habits in relationship to BMI in almost 16,000 youth in grades 6–10 who participated in the Canadian 2009/2010 Health Behaviour in School-Aged Children Survey (HBSC).

Participants reported the frequency of snacking while watching television and the frequency of eating junk food (sweets, soft drinks, baked goods, French fries, potato chips). Total hours per week of television were also calculated.

Although there was certainly a modest positive relationship between television viewing and BMI, this did not seem to be mediated by television snacking or junk food consumption. If anything, the relationship between the latter appeared to be slightly negative.

While there may well be all kinds of methodological and potential confounders of why these findings do not support the ‘hypothesis’ (increased snacking of junk food while watching TV is an important driver of childhood obesity), it certainly appears that this effect, even if it exists, is probably far less powerful than most of us would expect.

Sure, self-reported data (not just in kids) should always be taken with a grain (or teaspoon?) of salt, but then again, one would need to hypothesize that skinny kids are perhaps more ‘truthful’ about reporting their behaviours, something for which there is even less evidence. And yes, the study does not tell us about general snacking or junk food consumption outside of TV viewing but other studies have shown that the commonly held notion that fat kids apparently live on a staple of unhealthy junk foods and soda pop while skinny kids are more likely to be weight-conscious organic vegans, is not exactly true either.

The key learning for me from such studies is merely that much of what we so often assume as the ‘key drivers’ of obesity do not appear to be all that ‘key’, when we look at the actual studies published on these issues (regular readers may recall the results of the Canadian Measurements Survey, which did failed to show that fat kids were any less active than skinny kids).

Obviously, such studies also almost never look at the ‘whys’ (rather than the ‘whats’), as this would be a whole different line of research.

Perhaps, when data does not support the stereotype, it is time to question the stereotype rather than the data.

Whistler, BC

ResearchBlogging.orgCarson V, & Janssen I (2012). The mediating effects of dietary habits on the relationship between television viewing and body mass index among youth. Pediatric obesity PMID: 22461393



  1. Perhaps, when data does not support the stereotype, it is time to question the stereotype rather than the data.

    Absolutely true, and seldom acknowledged in this area of study. The research seems to be 10% science, 90% attempted justification and expansion of existing biases. Thank you.

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  2. These are interesting findings, thanks for sharing them.

    Typically in science a reductionist approach dominates, and on this topic we don’t see anything different. The physical activity camp of obesity researchers will point to inactivity as the “key driver,” while the nutritionists will of course focus on diet as the primary predictor. Who is right? As with most things in life, the truth probably lies somewhere in the middle.

    Is physical activity an important component of healthy weight? Yes, but how important is probably a function of one’s context. For someone wishing to maintain a healthy weight it is probably more important then one wanting to lose weight. And as a part of a healthy lifestyle it certainly plays an important role because of its other benefits.

    My interpretation of childhood obesity is that diet is probably driving the problem more than inactivity. Having said that, however, the health benefits of being active indicate that kids should be encouraged to get less screen time each day and more time being active—however one defines that, i.e. organised sports, unstructured play, frisbee or just walking in the neighborhood with one’s family.

    It is too easy to peg one issue as the key driver, especially when obesity is the result of a complex interaction between our genes and our environment. Plus, the message of “Get more active” resonates and seems to “make sense” for most, so I doubt this will go away any time soon. Hopefully, as with most ideas in science that are initially rejected, it eventually becomes self-evident, a la, “We knew that all along!”

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  3. Sports Scientist, a would bet my retirement account that the key driver in “childhood obesity” is not activity or diet. It is genetics. Most people who are classified as obese in childhood are predisposed to have larger builds, are either muscular, fat, or both, and often have what used to be referred to as “large frames.”

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  4. Hi Arya,
    To prevent from obesity we must workout regularly and have balanced diet meal plan. Avoid skipping meals and break meals in small frequent meals. Prefer raw food over processed food, increase water intake and have green tea. Do not eat late and manage stress with regular workouts.

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