At the same time, the incidence of obesity has risen sharply in the last 10 years. No wonder we are being called a couch potato-society! But is there an association between these two trends? Is the time you spend in front of the screen increasing your chances of gaining weight? Is it hindering your chaces of living a longer life?
The Association Between TV Viewing And Obesity
Research has shown consistently that TV viewing relates positively to body weight. Passive entertainment through television has been suggested as a contributing factor to the alarming rise in obesity. Risk for overweight is substantially higher among families who watch TV 6 or more hours a day. Even at modest levels of TV watching (1 hour a day) an association with obesity is still noted [2].The Nurses’ Health Study, which analyzed the sedentary behavior of 50,000 women aged 30 to 55 years, provided strong evidence that prolonged TV watching is directly related to obesity. For each 2-hour/day increase in time spent watching TV, the risk of these women becoming obese increased by 23% [3]. Many studies have confirmed a positive association between TV viewing and body mass index in both children and adults.
Does Watching TV Make You Fat?
Ok, research shows that people who watch TV tend to be overweight. But does this infer causation? Which came first, the obesity or the TV habit? In other words, is it the very act of watching TV that somehow increases your chances of becoming overweight or is it certain aspects of the specific lifestyle of the average heavy TV viewer (i.e unhealthy diet, reduced physical activity) that account for the observed TV-obesity association?Well, a number of very plausible explanations have been proposed in favor of TV viewing having a causal effect on obesity. First of all, the TV-obesity relation is observed even among people who exercise and lead an overall healthy lifestyle. Stated differently, when diet and exercise habits are factored in, the association between TV viewing and obesity still remains. Therefore, although it is true that those who watch more TV tend to engage in lower levels of vigorous activity, this by itself cannot explain the link between TV viewing and obesity.
How Can TV Sabotage Your Weight Loss Efforts
Here are some mechanisms by which TV viewing can impact on your weight, which do not rely upon TV viewing “displacing” your physical activities.You Eat More
Eating in front of the TV increases your meal intake especially of sweet, high fat snacks. In a sample of 78 mostly female undergraduate students, eating behavior was compared between days when meals were consumed with the TV on and days when TV was off while eating [4]. Participants ate more often on days when they ate with the TV on—one extra meal—resulting in higher calorie intake, specifically of fat and sugar. The amount eaten was proportional to the time spent in front of the TV.
In a similar study, 48 women were served 4 lunch meals and were instructed to eat two of them in a quite room and the other two while watching TV [5]. The subjects ate 13.4% more calories in the presence of TV. But why is it that you tend to eat more when eating with the TV on?
First, food is widely portrayed on TV. In a typical 1-hour TV segment, you are exposed to approximately 11 food and beverage appetizing commercials. The most heavily promoted foods are high in fat and sugar, a pattern that contradicts the recommendation of the Food Guide Pyramid. In contrast, healthy foods, such as fruits, vegetables and complex carbohydrates, are rarely featured.
Second, the attention paid to the TV distracts you from your concurrent eating behavior. It prevents you from listening to your “internal processing food cues” and “exerting your habitual dietary restraint”, researchers note.
You Have A Lower Metabolic Rate
Studies show that when you watch TV you spend less energy than when you rest. If two people were to do nothing but either watch TV or rest without watching TV for a whole day, the one who watches TV would spend 211 fewer calories [6]. Television viewing has a lowering effect on metabolic rate. In fact, when you watch TV you spend almost as much energy as you spend while sleeping.
You Eat More At Subsequent Meals
A recent study showed that the effects of television on food intake extend beyond the time of TV watching to affect later consumption. Specifically, television watching during lunch time increases afternoon snack intake [7].
The participants, 16 normal-weight young women students, consumed a meal either watching a 10 minute video clip played on a TV or in the absence of the clip. The lunch was the same in both situations. Two and a half hours later the participants were given cookies as an afternoon snack and were asked to eat as much as they wished. None of the women were alerted to the purpose of the experiment.
Participants ate more cookies in the afternoon snack following the lunch with TV than following the lunch at which they had not watched TV. Why is it that watching TV while you eat can make you consume more food at a later meal?
Researchers believe that the distraction of your attention away from the meal while watching TV makes it more difficult for you to recall this meal. So, why is that important that you remember your last meal? Studies have shown that how much we eat at a certain meal depends on the information we have in memory about the most recently consumed meal. This also explains why amnesiacs overeat compared to normal people when offered multiple meals.
In the above experiment, the participants were asked to rate how vividly they could remember the lunch that they ate. Interestingly, the women who ate their lunch watching TV had lower vividness of lunch recall than those who ate in the absence of TV.
How Can You Avoid The Fattening Effect of TV Viewing?
Become more active – Reduce TV viewing. The Nurses’ Health Study suggested that 30% of people who are on a trajectory to becoming obese can avoid that by watching less than 10 hours a week TV and taking a brisk walk for a minimum of 30 minutes a day.Ways to limit TV viewing include removing televisions form your bedroom and kitchen and using devices to limit access. As an adult, by simply substituting 30 minute of TV viewing with slow-paced walking, you will expend energy equivalent to 6.6 lb weight loss over the course of a year.
Avoid Eating While You Watch TV. Separating the acts of television viewing and food consumption will diminish the stimulus effect of TV viewing on eating. Consuming your meal undistracted by TV raises awareness of what is eaten and will make you more sensitive to inhibitory satiating factors. It will also better register the eating event in your memory and help you control later snack intake.
Conclusion
Energy intake has the tendency to increase with longer television viewing. A repeated consumption of meals in the presence of TV can lead to excessive food consumption over a long period of time, and facilitate development of overweight. Reducing the time you spend watching TV, can help you in your weight loss effort by decreasing your overall daily food consumption.About The Author
Matthew Denos, PhD, is a biology scientist and writer who is concerned about the obesity epidemic. His articles, based on peer-reviewed journals, touch on practical issues related to daily life. His blog, devoted to weight loss program reviews, can be visited at WeightLossTriumph.com.
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References
1. http://latimesblogs.latimes.com/technology/2008/11/americans-now-w.html
2. Altering TV viewing habits: an unexplored strategy for adult obesity intervention? Foster JA, Gore SA, West DS. Am J Health Behav. 2006 Jan-Feb;30(1):3-14. Review.
3. Television watching and other sedentary behaviors in relation to risk of obesity and type 2 diabetes mellitus in women. Hu FB, Li TY, Colditz GA, Willett WC, Manson JE. JAMA. 2003 Apr 9;289(14):1785-91.
4. Television viewing is associated with an increase in meal frequency in humans. Stroebele N, de Castro JM. Appetite. 2004 Feb;42(1):111-3.
5. Non food-related environmental stimuli induce increased meal intake in healthy women: comparison of television viewing versus listening to a recorded story in laboratory settings. Bellisle F, Dalix AM, Slama G.
6. Effects of television on metabolic rate: potential implications for childhood obesity. Klesges RC, Shelton ML, Klesges LM. Pediatrics. 1993 Feb;91(2):281-6.
7. Television watching during lunch increases afternoon snack intake of young women. Higgs S, Woodward M. Appetite. 2009 Feb;52(1):39-43. Epub 2008 Jul 23.
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