PEDIATRICS Vol. 118 No. 6 December 2006, pp. e1831-e1835 (doi:10.1542/10.1542/peds.2006-1087)
ARTICLE |
Energy Expenditure of Sedentary Screen Time Compared With Active Screen Time for Children
a Endocrine Research Unit
b Department of Family Medicine, Mayo Clinic, Rochester, Minnesota
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ABSTRACT |
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 TOP ABSTRACT METHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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OBJECTIVE. We examined the effect of activity-enhancing screen devices on children's energy expenditure compared with performing the same activities while seated. Our hypothesis was that energy expenditure would be significantly greater when children played activity-promoting video games, compared with sedentary video games.
METHODS. Energy expenditure was measured for 25 children aged 8 to 12 years, 15 of whom were lean, while they were watching television seated, playing a traditional video game seated, watching television while walking on a treadmill at 1.5 miles per hour, and playing activity-promoting video games.
RESULTS. Watching television and playing video games while seated increased energy expenditure by 20 ± 13% and 22 ± 12% above resting values, respectively. When subjects were walking on the treadmill and watching television, energy expenditure increased by 138 ± 40% over resting values. For the activity-promoting video games, energy expenditure increased by 108 ± 40% with the EyeToy (Sony Computer Entertainment) and by 172 ± 68% with Dance Dance Revolution Ultramix 2 (Konami Digital Entertainment).
CONCLUSIONS. Energy expenditure more than doubles when sedentary screen time is converted to active screen time. Such interventions might be considered for obesity prevention and treatment.
Key Words: physical activity • obesity • indirect calorimetry • television • video games
Abbreviations: REE—resting energy expenditure
Obesity prevalence among children is at the highest levels measured; presently 15% of US boys and girls 6 to 11 years of age are overweight.1 Obesity among children has increased more rapidly in the past 30 years. Obesity is a global epidemic with unheralded health consequences.2 These increasing obesity rates have been blamed, in part, on increasing sedentariness.3 Sitting in front of a television, video game, or computer screen has been associated consistently with low levels of physical activity.4 Weekly screen time for children is as high as 55 hours/week,5 and the average home in the United States has a television on for 8 hours per day.6 Although many programs have attempted to separate children from the screen, these activities are highly valued and children are resistant to relinquishing them.7 An alternative approach is to examine whether sedentary screen time can be converted into active screen time.
Several activity-promoting video games directed at children exist and have the potential to promote physical activity during screen time.8 A key question is whether these activities are sufficiently exothermic to result in increased energy expenditure. On one hand, if these activity-promoting maneuvers increase energy expenditure only minimally, then their applicability for reversing sedentariness would be limited and these approaches would offer false promise. On the other hand, if approaches to render screen time active increase energy expenditure substantially, then they could become potent tools for reversing sedentariness while permitting highly valued screen-based activities. In this study, we examined the energy expenditures of approaches that render screen time active and compared these values with values for activities performed seated among children.
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METHODS |
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Subjects
Twenty-five healthy children (12 boys and 13 girls) of varying heights and weights were recruited (Table 1). Ten children (5 boys and 5 girls) with mild obesity (85th percentile
BMI 99th percentile) were recruited (Table 1). The remaining children (7 boys and 8 girls) were of normal weight (5th percentile < BMI < 85th percentile). The children underwent clinical evaluations and physical examinations. Each child's weight and height were measured with a calibrated digital scale (Scale-Tronix 5005 stand-on scale; Scale-Tronix, White Plains, NY) and a fixed stadiometer, respectively. BMI percentiles and z scores were determined by using Centers for Disease Control and Prevention growth charts. Children who had acute or chronic diseases or were receiving any medications were excluded. The study was approved by the Mayo Clinic Pediatric and Adolescent Medicine Research Committee and the institutional review board. Informed written assent was obtained from the children, and informed written consent was obtained from the parents.
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Procedures
Energy Expenditure
Energy expenditure was measured by using a high-precision, flow-over, indirect calorimeter built specifically for use with children (Columbus Instruments, Columbus, OH).9 Expired air was collected with a dilution facemask that was designed for use with children and that covered the entire face. A primary gas standard (0.50% carbon dioxide, 20.5% oxygen, and balanced nitrogen) was used for gas calibrations before each measurement. Data were collected every 30 seconds and stored on a personal computer. Weekly alcohol burn experiments showed carbon dioxide and oxygen recoveries of
99%.
Video Game Systems and Games
In the children's study, 2 video game systems were used (PlayStation 2; Sony Computer Entertainment, San Mateo, CA, and Xbox; Microsoft, Redmond, WA). Three video games were used, namely, 1 video game played while seated and 2 activity-promoting video games. The video game that was played while seated used a hand-held controller connected by a cable to the game system (PlayStation 2) and was called Disney's Extreme Skate Adventure (Activision, Los Angeles, CA). The first activity-promoting video game used a small USB camera (EyeToy; Sony) to place the child into the game, to catch objects interactively, for example (Nicktoons Movin'; THQ, Calabasas Hills, CA; PlayStation 2 format). The second activity-promoting video game used a floor dance pad as the game controller, with children dancing in a certain format to gain points (Dance Dance Revolution Ultramix 2; Konami Digital Entertainment, Redwood City, CA; Xbox format).
All of the games were rated E (for everyone) by the Entertainment Software Rating Board and were shown to the parents for approval during the screening visit. During the study, all children played the same video games with the same game settings. (1) For Disney's Extreme Skate Adventure, all children played with the character Woody and started the game in Andy's room. (2) For Nicktoons Movin', all children played the Jellyfish Jam game repeatedly. (3) For Dance Dance Revolution Ultramix 2, all children played to the song "Samba" in the training mode, with the game speed set at level 3.
Protocol
First, children attended a screening visit, in which children and parents were familiarized with the calorimeter and all procedures. On the day of the study, children were asked to come to the General Clinical Research Center. Children were instructed to arrive after 5 hours of fasting, although they were allowed water.
The child rested in a dimly lit room for 30 minutes. Resting energy expenditure (REE) was then measured for 20 minutes by using indirect calorimetry, as described above. During the REE measurement, the child was awake, semirecumbent (10° head bed tilt), lightly clothed, and in thermal comfort (68–74°F), in a dimly lit room. The child was encouraged not to talk or to move during the REE measurement.
After measurement of REE, the child was given a snack, to reduce hunger and irritation. After the snack, the child was directed to sit motionless for 15 minutes while being supervised. Children watched an age-appropriate videotape while sitting. Energy expenditure was then measured for 15 minutes as described above. The indirect calorimeter mask was removed, and the child was allowed to rest for 5 minutes.
The child was allowed to play the traditional video game (Disney's Extreme Skate Adventure) for 
3 minutes, to become familiar with the game. Energy expenditure was then measured for 15 minutes while the child played the traditional video game while seated. The calorimeter mask was removed, and the child was allowed to rest for 5 minutes.
The child then watched a videotape (rated G) while walking on a treadmill at 1.5 miles/hour. This is a velocity that we showed previously was an enjoyable self-selected velocity for children of this age.9 Energy expenditure was measured for 15 minutes as described above. The child then rested for 5 minutes.
The child was then allowed to play the first activity-promoting video game (Nicktoons Movin') for 3 minutes for familiarization. Energy expenditure was measured for 15 minutes while the child played the game. After a 5-minute rest, the second activity-promoting video game (Dance Dance Revolution Ultramix 2) was played. After 3 minutes for familiarization, energy expenditure was measured for 15 minutes while the child played the game. Children were allowed to drink water during the rest period.
Statistical Analyses
Values are expressed as mean ± SD. Height, weight, age, gender, BMI, and energy expenditure were calculated for each participant. To address our hypothesis that energy expenditure would be significantly greater when children played interactive video games, compared with sedentary video games, energy expenditures determined by using indirect calorimetry while children played the 3 video games were compared numerically. To compare changes in energy expenditure, analyses of variance with posthoc paired t tests (Tukey-Kramer) were used. Statistical analyses were conducted with StatView 5.0 (SAS Institute, Cary, NC).
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RESULTS |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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All children in the study tolerated the protocol well and enjoyed participating in the study. Characteristics of the children are presented in Table 1. For the entire group, the children (10 ± 2 years of age; 12 boys and 13 girls) were of varying height (144 ± 11 cm) and weight (41 ± 10 kg); BMI was 20 ± 4 kg/m2. Fifteen of the children were considered lean, according to their BMI (15th percentile < BMI < 85th percentile; mean BMI percentile: 58 ± 23; mean BMI z score: 0.15 ± 0.77), and 10 children were overweight or at risk for overweight (BMI of
85th percentile; mean BMI percentile: 92 ± 5; mean BMI z score: 1.6 ± 0.5). Twenty-two children were white/not of Hispanic origin, 2 children were Asian, and 1 child was black/not of Hispanic origin. Values for REE and expenditure during the various activities (adjusted for body weight) are shown in Table 1 and Fig 1. All activities showed increased energy expenditure over REE. Seated television watching and video gaming were associated with increases of 50 ± 29 kJ/hour (P < .0001) and 55 ± 29 kJ/hour (P < .0001), respectively, in energy expenditure over rest (Fig 1).
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Walking while watching television increased energy expenditure by 353 ± 118 kJ/hour (P < .00001) in comparison with REE and by 302 ± 105 kJ/hour (P < .00001) in comparison with sitting and watching television. Activity-promoting video games were associated with a far larger increase in energy expenditure, compared with playing a video game while seated. For the EyeToy, energy expenditure increased 273 ± 101 kJ/hour above REE (P < .00001). For the Dance Dance Revolution Ultramix 2, energy expenditure increased 382 ± 181 kJ/hour above REE (P < .00001). There were significantly greater increases in energy expenditure for the EyeToy and Dance Dance Revolution Ultramix 2, compared with sitting and watching television and seat-based video gaming (P < .00001). Therefore, activity-promoting video games are associated with substantial increases in energy expenditure, compared with seat-based screen activities. There were no significant differences in energy expenditure based on gender or age.
To address the hypothesis that lean children expend more energy in playing activity-promoting video games, compared with overweight children, we compared the energetic responses to these seat-based and activity-promoting video games between lean and overweight children. In absolute terms, the obese children had significantly greater increases in energy expenditure in response to the activity-promoting video games (Fig 1). When the data were corrected for body weight, overweight children had significantly lower energy expenditure for resting (lean: 7.1 ± 1.3 kJ/hour per kg body weight; overweight: 5.9 ± 0.8 kJ/hour per kg body weight; P < .02), sitting and watching television (lean: 8.4 ± 1.7 kJ/hour per kg body weight; overweight: 7.1 ± 1.3 kJ/hour per kg body weight; P < .03), and sitting and playing the traditional video game (lean: 8.4 ± 1.7 kJ/hour per kg body weight; overweight: 7.1 ± 0.8 kJ/hour per kg body weight; P < .05) (Table 1). However the energetic responses were not significantly different between the groups for walking and watching television or playing the activity-promoting video games (Table 1). It was clear that the increase in energy expenditure associated with activity-promoting video games was intact in obesity.
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DISCUSSION |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Obesity rates in children and adults have reached unprecedented levels. Obesity-associated chronic diseases, such as type 2 diabetes mellitus, are now commonly being diagnosed in children and are increasing in incidence in adults. One factor that is thought to be important in obesity pathogenesis is low activity levels or low non-exercise activity thermogenesis.10,11 It is recognized that an important factor in understanding sedentariness is the many hours each day that people engage in seated screen-based activities, such as television watching, video gaming, and operating a computer. Our objective in this study was to examine the energetic implications of converting seat-based screen time to activity-based screen time. Activity-promoting video games and treadmill television and computer use more than doubled energy expenditure, compared with the chair-based equivalents. We suggest that activity-promoting video gaming and computer use is one potential approach for reversing sedentariness.
Low activity levels that are coupled to, on average, 8 hours of screen time per day are widely recognized as major factors in obesity. Many attempts have been made to promote activity at home, at school, and in the workplace.12 Part of the problem is that children value screen-based activities; therefore, attempts to have children replace their gaming with less-valued activities, such as walking in the park, often fail.13,14 If sedentary screen time could be converted effectively to activity, then this could be an effective approach for promoting physical activity. Our question was whether activity-promoting screen time increases energy expenditure substantially, because this might prompt studies to examine these modalities for weight loss.
Although our data demonstrated clearly that activity-promoting screen time increases energy expenditure in children dramatically, the study has limitations. First, this was not a long-term weight loss study. Our goal was to evaluate the energetic potential of converting sedentary screen time to activity-promoting screen time. We think that these data are sufficiently robust to warrant prospective, randomized studies in this area. Second, the experiments were conducted in a laboratory, rather than at home. We do not think that a home-based study would have altered substantially our primary finding that activity-promoting screen time doubles energy expenditure, compared with seat-based screen time. Our study was relatively small; however, it was conducted very carefully, so that a larger study would have been unlikely to alter the primary findings. We did not randomize the order of the study protocol between study participants. Randomization of the protocol activities would have extended the length of the study protocol from 3 hours to 6 hours, making it more difficult for young children to participate. Finally, the children received a small snack, which might have increased energy expenditure above REE by 5%. This was ethically mandatory to prevent the children from feeling excessively hungry. It did not affect our primary results. Despite the limitations, it is clear that activity-promoting video games can increase screen-associated energy expenditure dramatically.
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CONCLUSIONS |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Activity-promoting video games have the potential to increase energy expenditure in children to a degree similar to that of traditional playtime.15,16 Classic behavior models and large numbers of video-gaming units and computers suggest that children are spending more time in front of screens than they did previously. Furthermore, projections indicate that screen time for children is likely to continue to increase, rather than decrease. We think that converting seat-based screen time to activity-associated screen time is an essential approach for promoting an active environment that is also fun for children.
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ACKNOWLEDGMENTS |
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This work was supported by National Institutes of Health grants DK50456, DK56650, DK63226, DK66270, and M01-RR00585. Support was also provided by the Mayo Clinic Department of Family Medicine Small Grants Program.
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FOOTNOTES |
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Accepted Jul 13, 2006.
Address correspondence to James A. Levine, MD, PhD, Endocrine Research Unit, 5-194 Joseph, Mayo Clinic, 200 First St, SW, Rochester, MN 55905. E-mail: levine.james{at}mayo.edu
Drs Lanningham-Foster and Levine and Mr Foster had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
The authors have indicated they have no financial relationships relevant to this article to disclose.
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PEDIATRICS (ISSN 1098-4275). ©2006 by the American Academy of Pediatrics
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