Childhood obesity’s relationship to time spent in sedentary behavior

Childhood obesity’s relationship to time spent in sedentary behavior

Arluk, Shaye L

Objective: The purpose of this study was to evaluate various types of sedentary behavior children participate in and to look for an association to childhood obesity. Methods: Questionnaires were used to gather data on physical and sedentary activity, dietary intake, demographics, and anthropometrics of 9- to 12-year-old military dependents and their parents. Results: Using body mass index (BMI), 39.8% of children were obese. A significant relationship was found between childhood obesity and computer usage, television watching, total hours in sedentary behavior, and maternal BMI. An indirect significant relationship with childhood obesity was also shown if a parent was home when the child got home from school and if a father participated in exercise with their child. Caloric intake, total time in physical activity, demographic variables, and father’s BMI showed no significant relationship with children’s BMI. Conclusion: Interventions should be designed targeting total time spent on the computer, total time watching television, and maternal obesity in child obesity programs.

Introduction

According to the 1999 National Health and Nutrition Examination Survey, approximately 13% of children age 6 to 11 years old and 14% of children age 12 to 19 years old are overweight (body mass index [BMI] values greater than the 95th percentile).1 The prevalence of overweight children has more than doubled since the first nutrition examination survey, which was conducted over 30 years ago. Numerous studies have investigated the detrimental effects of childhood obesity as well as other factors associated with childhood obesity such as heredity, dietary intake, exercise fitness level, and social environment.2-8 The role of physical inactivity in childhood obesity has received specific attention with television viewing time9,10 and decreased physical fitness level11 reported to be strongly correlated with childhood obesity.

Although research has investigated the association between television viewing time and childhood obesity, the inactive time of Americans today can be related to more than just time spent in front of the television. With the boom of the technology age, it has been observed that American adults’ sedentary time has increased dramatically. Has technology done the same to our children? Children today have many activities they participate in that require little energy expenditure. Computers, the Internet, real-life video games, and chat lines are all media that could also contribute to the rise in childhood obesity over the last 20 years. The effect of total time spent in sedentary activity on childhood obesity has been sparsely covered in the literature. The children of U.S. Navy personnel are a seldom-studied population for which there is a high prevalence of childhood obesity as observed by dietitians and pediatricians in the outpatient clinics. Therefore, the purpose of the present study was to examine the relationship between sedentary behaviors and childhood obesity in U.S. Navy dependents.

Methods

Sample

A cross-sectional convenience sample of 101 children, ages 9 to 12 years, from Navy families in the Hampton Roads, Virginia area were used for this study. Children received survey packets with three questionnaires when they checked into the pediatric clinics at the Naval Medical Center Portsmouth and Boone Pediatric Clinic in September 2000. Five hundred surveys were made available to the clinics, resulting in a return rate of 20.2%. However, later questioning of the house staff revealed 150 surveys were never handed out, changing the response rate to 29%. Inclusion criteria were subjects who completed all three questionnaires and had no documented endocrine or metabolic disorder that could precipitate obesity. Before beginning the research, permission was obtained from the Human Subject/Institutional Review Board at Old Dominion University as well as the Internal Review Board at the Naval Medical Center Portsmouth. The cover letter to the survey packet stated that parent and child consent to use the information was acknowledged by return of the surveys to the clinics.

Measures

Every day for 1 month, parents of children attending the Pediatric or Nutrition Clinic at the Naval Medical Center Portsmouth or Boone Clinic in Virginia Beach were handed a survey package upon check-in. The children’s survey was a 17-item questionnaire, designed from a previous validated instrument,12 entitled Adolescent Lifestyle Questionnaire. The questionnaire determined factors related to time spent in vigorous and moderate level activity as well as time spent in sedentary activity. In addition, the last seven questions of the questionnaire included a modified 24-hour recall. Also included in the survey packet was a weekly food frequency questionnaire with standardized instructions for completion. A parent questionnaire was also included for the parent or legal guardian who spends the most time with the child to complete. The parent survey was used to verify the children’s results on dietary intake and exercise as well as to obtain familial adiposity patterns.

Obesity

Self-reported heights and weights were available on 98 children, 88 mothers, and 81 fathers. Childhood obesity was defined as having a BMI greater than or equal to the 95th percentile as determined by the new pediatric growth charts.13 Children’s BMI were compared with the norms established by the National Health and Nutrition Examination Survey III expert committee in an attempt to control for maturation.14 Parent obesity status was defined as a BMI greater than or equal to 30 kg x m^sup -2^.15

Data Analysis

Data analysis was completed using the SPSS-7.0 program (SPSS Inc, 1995, Chicago, Illinois). Data were examined using frequency distributions and percentages. Nutrition V (First DataBank Division, 2000, San Bruno, California) was used to calculated macronutrient intake. Survey results were grouped into total time spent in sedentary behavior (hours per day) and total time in active behavior (hours per day). These values were used as a continuous factor to compare against childhood obesity. Using [kappa]-analysis, parent surveys were used as a reliability agent for the children survey answers. [Chi]^sup 2^ compared obesity status in children with various independent variables. Logistic regression was used to determine key variables in predicting childhood obesity. Unless otherwise indicated, reported values for continuous variables were mean + or – SD with a significance set at p

Results

Demographic characteristics of the subject population are shown in Table I. Males and females were evenly represented. Race distribution was comparable with the local population. The mean BMI for children was 23.2 + or – 7.2 kg x m^sup -2^. Based on the 95th percentile from the new pediatric growth curves, 59 (60.2%) were not obese and 39 (39.8%) children were obese.13 The mean BMI for fathers was 27.6 kg x m^sup -2^. Based on the National Institutes of Health clinical guidelines for obesity defined as having a BMI >30 kg x m^sup -2^, 59 (72.8%) fathers were not obese and 22 (27.2%) were obese.15 Twenty surveys did not provide enough information to determine BMI for the father. The mean BMI for mothers was 27.6 kg x m^sup -2^. Also based on the National Institutes of Health guidelines of adult obesity, 61 (69.3%) mothers were not obese and 27 (30.7%) mothers were obese.15 Both parents being obese made up 10.3% of the population studied.

Sedentary Activity

Mean daily television time during the week was 3.4 hours; weekend time was 4.4 hours daily. Mean daily time spent on the computer per week was 2.4 hours; weekend time was 3.0 hours daily. Total daily hours in sedentary activity, including time spent watching television, using the computer, playing video games, doing homework, and taking a nap, was computed at an average of 7.0 hours per day. Table II shows the significance between childhood obesity and various behaviors. A child was more likely to be obese if they spent greater than 2.3 hours per day on the computer or greater than 2.8 hours per day watching television during the week. A child was also more likely to be obese if they did not exercise with their father during the week or if a parent was not home when they got home from school.

Physical Activity

When children were asked how many days they participated in physical education classes, the mean value was 4.5 days per week. When children were asked to assess their exercise behavior compared with their peers, 18 (18%) children said they were a lot more physically active than most other kids, 18 (18%) reported being a little more physically active than other kids, 30 (30%) reported their physical activity level the same as most other kids, 16 (16%) reported being a little less physically active than other kids, and 18 (18%) reported being a lot less physically active than other kids. One child did not respond to this question.

Dietary Intake

The 24-hour recall using Nutritionist V software revealed 34.7% of children consumed a high-fat dinner (>40% of the total calories from fat) the night before, 5.1% had a low-fat dinner (

Childhood Obesity

When childhood obesity was compared against all the main independent variables (heredity, physical activity levels, sedentary behavior patterns, and dietary intake) using a logistic regression model, it was shown that the strongest independent predictor of childhood obesity was if the child’s mother was also obese. However, if the child participated in a large number of hours of sedentary activity daily there was also a strong association with obesity. The model had a sensitivity of 71% in identifying children who were obese.

Discussion

Demographic and Anthropometric Characteristics

Regarding the demographics of this study, males and females were fairly evenly represented, 43% and 50%, respectively. Using the [Chi]^sup 2^ goodness of fit test and information provided by the Bureau of Naval Personnel on the demographic make-up of active duty personnel as of December 31, 2000,16 the ethnic demographics did not show a significant similarity. The survey sample was more representatives of the local demographics,17 which has a higher African-American population than the national Navy demographics.

The main dependent variable of childhood obesity was reported as 39.8% of the population surveyed, which is significantly higher than the 14% reported by the 1999 National Health and Nutrition Examination Survey of overweight children. However, the findings of this survey should be compared with the findings of the national survey with caution, as the present survey used a much smaller sample size and encompassed a population that differed greatly by socioeconomic status and ethnic diversity. More comparable studies would include research by Moore18 on adolescent U.S. Army dependent girls and research by Tiwary and Holguin19 on U.S. Army dependents ranging in age from 1 year and older. These two studies found 40% and 33.3%, respectively, of children were considered above normal weight. The Virginia Department of Health reports regional childhood obesity to be 37% according to studies they have done in the area, which included military families.20 It should be noted that these three studies used the old pediatric growth charts that were based on the National Center for Health Statistics in 1979, whereas this study used the newly revised pediatric growth charts based on measurements of BMI as stated earlier.

Parental BMI as a contributing factor of child obesity has also been supported in the literature using similar age groups to this research8,21 as well as younger children.7 However, the three research studies referenced found childhood obesity highly correlated if either the child’s mother or father were obese or if both parents were obese. This research found the strongest correlation with maternal obesity but also a significant association with both parents being obese. No independent relationship was found with father’s BMI and the child’s BMI. As stated in the demographic data, these results may be contingent on the fact that the populations studied in this research were all military dependents. The majority of military personnel are male. In light of deployments, it can be assumed that the mother would spend much more time in the home and serve as the primary caregiver. Therefore, it is not surprising that a child’s obesity would have a higher correlation to the mother’s BMI in this population. Based on these findings, obesity education needs to focus on both the mother and child for a successful outcome to be obtained.

This study also supports a new finding to the literature. Childhood obesity is more likely if a parent is not home when a child gets home from school. This could be due to the unsupervised child choosing higher caloric snacks or being more sedentary after school without a parent to intervene. These are topics requiring further investigation.

Dietary Intake

Total caloric intake also showed no significant relationship with obesity in this population, consistent with other research findings on the subject.2,3,22 When total caloric intake was collapsed into a dichotomous variable based on the recommended daily allowance for this age group (2,500 kcal/day), 92% of the population reported not even meeting this level regardless of weight status. This may be explained by the fact that throughout the research completed on this subject, underreporting of caloric intake by children has been consistently noted, especially among obese children.22 However, in this study underreporting of nutrient intake was observed in both obese and nonobese children, and parent records correlated among most food groups with their children’s answers at a high significance level. Therefore, we can assume the numbers for dietary intake in this study were at least representative of reported caloric and macronutrient intake among the population studied.

Energy Expenditure

Physical activity levels also showed no significant relationship with obesity status, which supports findings by other researchers.7,21,22 The method for data collection of physical activity patterns was based on the research by Pate et al.23 as an interval level variable that allowed the children to rate their participation in light and hard exercise by numbers of days per week participated in during the last 14 days. Because sedentary patterns in this research were classified as number of hours per day in various activities, future research in this area would more accurately benefit from a physical activity recall. A more continu-ous variable could be directly compared with the activity recall the child survey used to calculate sedentary behaviors. This was not used in this study based on the findings by Johnson-Down et al.22 that activity recalls are limited in the child population because of their decreased cognitive ability to accurately record type, duration, and intensity of physical activity. However, because [kappa] analysis showed a very high correlation between parent and children responses in the areas of dietary intake and sedentary behavior patterns, it is assumed that the same correlation would have been seen if a physical activity recall was used in the population studied. As stated in other studies, excessive television viewing time has a relationship to childhood obesity.9 This research expanded the concept of sedentary behavior to include time spent using the computer, doing homework, napping, talking on the phone, and practicing an instrument. The research found that, in addition to television viewing, total time spent in sedentary behavior correlated with obesity. This supports research by Maffeis et al.11 who did not look at specific activities but did look at the comparison between metabolic rate and energy expenditure and its effects on obesity.

Limitations to our study include a small sample size, self-reported heights and weights and a sampling effect because it surveyed only those children who presented at the pediatrician’s office. Despite these limitations, it can still be hypothesized based on this study and the studies by Moore18 and Tiwary and Holguin19 that the military population does have a greater issue with childhood obesity than the civilian population. Researchers like Janz et al.24 have found that activity patterns established in childhood lead to the activity patterns maintained in adolescence and that these patterns are carried into adult life. It is therefore important to recognize this population at a young age and establish obesity education programs before a child’s behavior patterns to diet and exercise have been established.

Conclusion

In conclusion, the findings of this study suggest that childhood obesity is a multifactorial issue with a strong correlation with the obesity status of the maternal household member and time that the child spends in inactive behavior patterns. In addition, this study lends credence to the fact that 9- to 12-year-old children can accurately depict their lifestyle patterns both from a dietary and activity standpoint and that parents of this age group realistically see their children’s current activity level and obesity status. The alarming percentage of obesity found among military dependents in this study warrants future need to conduct a larger scale, multicenter study that also looks more in-depth at parental/child interaction in the areas of exercise and diet. It is important to incorporate data from multiple military sites to truly understand the scope and cost of this issue to the military. During the interim, planners of childhood obesity programs should keep the preliminary findings of this study in mind when developing programs for obese children and make sure that these programs incorporate not only a child component but a family-oriented approach stressing maternal correc-tive action as well. Programs that take all relevant variables into consideration will hopefully not only show a higher success rate in decreasing the prevalence of childhood obesity but also help to decrease the trend of adult obesity seen in this country.

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Guarantor; Shaye L. Arluk, MS RD HFI

Contributors: Shaye L. Arluk, MS RD HFI*; J. David Branch, PhD FACSM[dagger]; David P. Swain, PhD FACSM[double dagger]; Elizabeth A. Dowling, PhD[sec]

*10720 Pine Haven Terrace, Rockville, MD 20852.

[dagger]Undergraduate Exercise Science Program, Old Dominion University, Norfolk, VA 23529.

[double dagger]Wellness Institute and Research Center, Old Dominion University, Norfolk. VA 23529.

[sec]Old Dominion University, Norfolk, VA 23529.

Presented at 16th Annual Naval Medical Center Research Competition, Naval Medical Center Portsmouth in March 2001.

This manuscript was received for review in April 2002. The revised manuscript was accepted for publication in October 2002.

Reprint & Copyright (C) by Association of Military Surgeons of U.S., 2003.

Copyright Association of Military Surgeons of the United States Jul 2003

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