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To assess the association of time spent viewing television, videos and video games with measures of fat mass (BMI) and distribution (triceps and subscapular skinfold thicknesses (TSF, SSF)). Cross-sectional validated survey, self-administered to students to assess screen time (television, videos and video games) and lifestyle variables. Trained personnel obtained anthropometry. The association of screen time with fat mass and distribution, stratified by sex, was modelled with multivariable linear regression analysis, adjusting for potential confounders and correlation of observations within schools. State of Morelos, Mexico. Males (n 3519) and females (n 5613) aged 11 to 18 years attending urban and rural schools in Morelos. In males, screen time of >5 h/d compared with <2 h/d was significantly associated with a 0.13 (95% CI 0.04, 0.23) higher BMI Z-score, 0.73 mm (95% CI 0.24, 1.22) higher SSF and 1.08 mm (95% CI 0.36, 1.81) higher TSF. The positive association of screen time with SSF was strongest in males aged 11-12 years. Sexual maturity appeared to modify the association in females; a positive association between screen time and SSF was observed in those who had not undergone menarche (P for trend = 0.04) but not among sexually mature females (P for trend = 0.75). Screen time is associated with fat mass and distribution among adolescent males in Mexico. Maturational tempo appears to affect the relationship of screen time with adiposity in boys and girls. Findings suggest that obesity preventive interventions in the Mexican context should explore strategies to reduce screen time among youths in early adolescence.
Public Health Nutrition: 12(10), 1938–1945 doi:10.1017/S1368980009004881
Screen time and adiposity in adolescents in Mexico
´n Lajous
, Jorge Chavarro
, Karen E Peterson
, Bernardo Herna
Aurelio Cruz-Valde
, Mauricio Herna
and Eduardo Lazcano-Ponce
Center for Population Health Research, National Institute of Public Health, Av. Universidad 655, Col. Santa
Maria Ahuacatitla
´n, CP 62508, Cuernavaca, Morelos, Mexico:
Department of Epidemiology, Harvard School
of Public Health, Boston, MA, USA:
Department of Nutrition, Harvard School of Public Health, Boston, MA,
Department of Society, Human Development and Health, Harvard School of Public Health, Boston, MA, USA
Submitted 22 November 2007: Accepted 18 November 2008: First published online 23 February 2009
Objective: To assess the association of time spent viewing television, videos
and video games with measures of fat mass (BMI) and distribution (triceps and
subscapular skinfold thicknesses (TSF, SSF)).
Design: Cross-sectional validated survey, self-administered to students to assess
screen time (television, videos and video games) and lifestyle variables. Trained
personnel obtained anthropometry. The association of screen time with fat mass
and distribution, stratified by sex, was modelled with multivariable linear
regression analysis, adjusting for potential confounders and correlation of
observations within schools.
Setting: State of Morelos, Mexico.
Subjects: Males (n3519) and females (n5613) aged 11 to 18 years attending urban
and rural schools in Morelos.
Results: In males, screen time of .5h/d compared with ,2 h/d was significantly
associated with a 0?13 (95 % CI 0?04, 0?23) higher BMI Z-score, 0?73 mm (95 % CI 0?24,
1?22) higher SSF and 1?08 mm (95 % CI 0?36, 1?81) higher TSF. The positive association
of screen time with SSF was strongest in males aged 11–12 years. Sexual maturity
appeared to modify the association in females; a positive association between screen
time and SSF was observed in those who had not undergone menarche (Pfor
trend 50?04) but not among sexually mature females (Pfor trend 50?75).
Conclusion: Screen time is associated with fat mass and distribution among
adolescent males in Mexico. Maturational tempo appears to affect the relationship
of screen time with adiposity in boys and girls. Findings suggest that obesity
preventive interventions in the Mexican context should explore strategies to
reduce screen time among youths in early adolescence.
Body mass index
Triceps skinfold
Subscapular skinfold
Television viewing
Screen time
Consistent with worldwide trends, the prevalence of
obesity in Mexico is increasing
. Between 1999 and
2006, the proportion of adults who were overweight or
obese increased from 67 to 72 % in women and from 61 to
67 % in men
. Using international cut-off points, the
prevalence of obesity in 1999 was 5?5 % in pre-school
children and 19?5 % in children aged 5 to 11 years
Understanding behavioural determinants of youth
obesity trends is essential to developing effective public
health approaches to prevention and control in different
country contexts. In observational studies, television
viewing in children and adolescents has been associated
with increased adiposity and obesity
and predicted
high BMI, smoking, low cardiorespiratory fitness and high
serum cholesterol in early adulthood
. Randomized
trials to limit television time and computer use among
children in the USA resulted in a significant reduction of
and lower BMI, triceps skinfold thickness (TSF),
waist circumference and waist:hip ratio
. Decreases in
television viewing also mediated the effect of a middle-
school, interdisciplinary curriculum on obesity (classified
as BMI and TSF .85th percentile) in young adolescent
Previous studies of the association of screen time with
youth obesity have inconsistently assessed the use of
media other than television. Limited information on
demographic, lifestyle and reproductive factors for
chronic disease also may undermine the interpretability
of results due to confounding by unmeasured variables.
Furthermore, assessment of fat distribution in early pub-
erty through skinfold thickness in addition to fat mass
may unveil additional insights on chronic disease risk in
Mexican youths. In the present study, we examined the
association between time spent viewing television, videos
*Corresponding author: Email rThe Authors 2009
and video games and anthropometric measures of fat
mass and distribution in a large survey of adolescents in
the State of Morelos in Mexico.
Research methods and procedures
Study population
The data presented here derive from a large, representative
survey conducted in 1999 to assess the prevalence of
chronic disease risk factors in youths in the State of Morelos,
Mexico. The methods are described elsewhere
. Briefly,
the study included a sample of youths aged 11 to 24 years
attending public junior high schools, high schools and the
State university. The sampling unit was the school. The
study population comprised 13 293 individuals, 56% of
whom were female. The response rate was 98?6%. An
imbalance between males and females in the sample was
due to both an underlying distribution that favours females
and a higher response rate in this group. Signed informed
consent forms were obtained separately from the study
participants and from their parents prior to collection of
information. Participants were asked to complete a self-
administered questionnaire on general lifestyle, frequency
of food consumption, physical activity, drug use and
health-care use. The survey was conducted in classrooms
during school hours; anthropometry on all participants
was obtained by trained staff in school settings. The study
was approved by the Human Subjects Committee of the
National Institute of Public Health of Mexico.
Eligible individuals for the current analysis were 11 to 18
years of age with complete questionnaire and anthropo-
metric information. We excluded young adults between
19 and 24 years of age because we considered adolescence
the developmental stage most biologically relevant to the
emergence of chronic disease in early adulthood. To
reduce potential confounding by underlying conditions
associated with disability and related inactivity, we
excluded underweight individuals, defined as being
below the 15th percentile for BMI
and for TSF
The final analytic sample comprised 9132 participants,
62 % of whom were female. This sub-sample did not
differ significantly from the original sample with respect
to major sociodemographic characteristics.
Data collection
Screen viewing and physical activity were measured
using a questionnaire validated in Mexican youths
Individuals were asked about their usual daily hours
viewing television, videos and video games (never, ,1,
1–2, 2–3, 3–4, 4–5, 6–7 or .7) on weekdays, Saturdays
and Sundays. Computer use was not collected because
home computer use is uncommon in this population.
Eighteen per cent of participants reported total daily
screen time greater than 12 h. A weighted average of
hours of screen viewing (weekdays, Saturday and Sunday)
was computed to obtain an overall average screen time.
We categorized screen time as ,2, 2–2?9, 3–3?9, 4–4?9
and $5 h/d in order to limit the error introduced by
multitasking (e.g. playing video games while watching
television) and the influence of outliers. Total television
and total video/video games were similarly categorized.
A weighted average of hours of inactivity was calculated
using weekday and weekend hours of sitting down, using
private or public transportation, doing homework and
sleeping. The questionnaire also included eleven items to
evaluate weekly hours of recreational physical activities
(never, ,0?5, 0?5–2, 2–4 and 4–6)
. Weekly expenditure
of metabolic equivalents (MET) of moderate and vigorous
physical activity was estimated by multiplying the
responses to questions by the activity-specific energy
expenditure as reported by Ainsworth et al.
. Energy
intake was estimated from a 103-item FFQ adapted from
a questionnaire validated for the Mexican adult popula-
. Socio-economic status (SES) was assessed using
an index derived from a principal components analysis
for the Mexican population that includes number of
rooms in the house, people living in the household,
municipal services, sanitary conditions, educational level
of the mother’s most recent sexual partner, and owner-
ship of home, car, television, video recorder and tele-
phone. Three categories were constructed using tertiles of
the principal component score
Height, weight, TSF and subscapular skinfold thickness
(SSF) were measured using standardized procedures by
trained personnel. Height and weight were measured
using daily gauged portable stadiometers and portable
Tanita scales (Tanita Corp., Itabashini-Ku, Tokyo, Japan),
respectively. For skinfolds, the average of three mea-
surements using Lange callipers (Beta Technology, Inc.,
Santa Cruz, CA, USA) was used and expressed in milli-
metres. BMI was calculated as weight/height
using the measured anthropometric data. Age- and sex-
specific standard deviation scores (Z-scores) for BMI were
calculated using the 2000 guidelines of the Centers for
Disease Control and Prevention
. The age-specific cut-
off points for overweight and obesity of the International
Obesity Taskforce were used to estimate their prevalence.
These cut-off points use an international reference
population comprising children and adolescents from six
different countries
. These cut-offs were used for
descriptive purposes only, to permit comparisons of BMI
distribution with other countries.
Statistical analysis
We analysed females and males separately. Means and
standard deviations were estimated for screen viewing
time within categories of selected participant character-
istics and the distribution was compared across categories
with the Kruskal–Wallis test. For ordinal predictors,
we tested for linearity using linear regression. Next, we
constructed linear regression models to explore the
Screen time and adiposity in adolescents 1939
association of BMI Z-scores, TSF and SSF with screen time
using the SAS SURVEYREG procedure to account for the
non-independence of the observations given that the
primary sampling unit was the school and that observa-
tions within schools may be correlated (SAS version 8;
SAS Institute Inc., Cary, NC, USA). Potential confounders
of these associations considered in the multivariable
model included age, height, SES tertile, single-parent
family, birth in a hospital, father’s educational level,
mother’s educational level, family income, family health
insurance, weekly MET of moderate-to-vigorous physical
activity, daily hours of inactivity excluding screen time,
type of community (urban, suburban, rural), total energy
intake, diagnosis of asthma, dieting and frequency of
restaurant dining. Given the rapid change in adipose tis-
sue distribution, linear growth, metabolic and hormonal
environment during adolescence, we hypothesized that
age would modify the relationship of screen time with
adiposity. Based on the results of this analysis we con-
sidered post hoc sexual maturity as another potential
effect modifier. Sexual maturity was also considered a
confounder. Females who had undergone menarche and
males who reported having had an ejaculation were
considered sexually mature. We also considered living in
a rural environment and moderate-to-vigorous physical
activity to be modifiers of this relationship because phy-
sical activity affects adipose tissue and individuals in a
rural environment may be more active. Results are pre-
sented as age-adjusted and multivariate-adjusted.
Table 1 shows the characteristics of the study population.
Male adolescents reported a higher energy intake and
greater MET of moderate and vigorous physical activities
than females. After transforming questionnaire categories
on media use to continuous variables, among males, a
greater amount of total daily hours of screen time was
spent watching television (2?7(
SD 1?9) h) than watching
videos (1?9(
SD 1?8) h) and playing video games (1?8(SD
1?9) h). On average, females spent 2?8(SD 1?9) h watching
television, 1?6(
SD 1?8) h on videos and 1?3(SD 1?8) h
playing video games every day. Menarche was reported
by 5229 (93?2 %) of female participants. The prevalence
of obesity was slightly higher in males; approximately
one-third of males and females were overweight.
Total daily screen time by different sociodemographic
characteristics is described in Table 2. Significant differences
in the mean daily screen time were observed for age, type
of community, SES and medical insurance in males and
females (P,0?01). Adolescent girls who reported they were
dieting to lose weight reported significantly less screen time
Table 1 Characteristics of 9132 Mexican adolescents from public schools in Morelos, Mexico (1999)
Males (n3519) Females (n5613)
Variable Mean SD Mean SD
Age (years) 13?81?813?91?7
Energy intake (kJ/d) 17 975 5306 16 670 5332
Moderate-to-vigorous physical activity (MET/week) 110 42 90?847?3
Total screen time* (h/d) 5?93?05?43?0
BMI (Z-score) 0?48 0?97 0?58 0?84
Triceps skinfold thickness (mm) 14 7 22 7
Subscapular skinfold thickness (mm) 11 5 15 5
Obesity-(%) 6?76?0
Overweight-(%) 30?030?5
Mean age at menarche (years) 11?41?1
MET, metabolic equivalents.
*Average daily hours of viewing television, videos and video games combined.
-International Obesity Taskforce cut-off points for BMI for age and sex
Table 2 Daily hours of television, video and video game use by
sociodemographic characteristics of Mexican adolescents from
public schools in Morelos, Mexico (1999)
Males Females
Variable Mean SD Mean SD
Age (years)
11–12 5?92?95?63?0
13–14 5?73?15?33?0
15–16 6?02?94?72?9
17–18 6?62?76?13?0
Community type
Rural 5?33?15?13?0
Suburban 5?92?94?93?0
Urban 6?62?86?12?9
Socio-economic status
Low 6?22?95?13?1
Medium 5?33?15?23?0
High 6?62?75?82?9
Medical insurance
Uninsured 6?22?95?53
Insured 5?73?05?33?0
To lose weight 6?13?15?03?0
To gain weight 6?13?16?22?8
Not on a special diet 5?93?05?43?0
1940 M Lajous et al.
than those who said they wanted to gain weight. Mean
screen time increased significantly with the level of urba-
nicity and, in females, screen time increased with increasing
SES (P,0?01). Energy intake increased significantly with
increasing screen time in males and females (P,0?001).
The mean daily energy intake in males was 15 305 kJ for
,2 h of screen time/d and 18 759 kJ for .5 h/d. Females
had a mean daily energy intake of 15 166 kJ for ,2h of
screen time/d and 17 581 kJ for .5h/d.
In males, screen time was positively related to BMI
Z-score in age-adjusted and multivariate-adjusted ana-
lyses. In the multivariate-adjusted model, males with .5h
screen time/d had a 0?13 (95 % CI 0?04, 0?23) higher BMI
Z-score compared with males with ,2 h/d (Pfor trend
,0?003). In females, screen time was positively related
with BMI Z-score in age-adjusted analyses but not in
multivariate-adjusted analyses (Table 3).
Screen time was positively related to TSF and SSF in
males. After adjusting for confounding variables, males
with .5 h of screen time/d had a 1?08 mm (95 % CI 0?36,
1?81) greater TSF compared with males reporting ,2 h/d
(Pfor trend 50?01). Similarly, after adjusting for con-
founding variables, males with .5 h of screen time/d had
a0?73 mm (95 % CI 0?24, 1?22) greater SSF compared with
males with ,2 h/d (Pfor trend 50?006). In females,
screen time was positively related to TSF and SSF in age-
adjusted but not multivariate-adjusted analyses.
Age did not modify the association between screen time
and BMI Z-score or TSF in males or females. Nevertheless,
the association between screen time and SSF differed sig-
nificantly by age categories in males (Pinteraction 50?005).
A significant linear trend of increasing SSF with greater
screen time was found in younger but not older males
(Fig. 1). In females, age did not modify the association
between screen time and SSF. The association was however
modified by sexual maturity; screen time was positively
related to SSF among females who had not undergone
menarche (Pfor trend 50?04) but not among sexually
mature females (Pfor trend 50?75; Fig. 2).
Males spent 54 % of their screen time on videos and
video games, while females spent 48 %. For males, we
found a significant increasing trend only in BMI Z-score
when we analysed videos and video games indepen-
dently of television (P50?03). No association with tele-
vision by itself was found. In females, no associations
were observed when television and videos/video games
were analysed independently.
The present study evaluated the association between time
spent viewing television, videos and video games and
measures of fat mass and distribution in a large survey of
Mexican adolescents in the State of Morelos. In males,
BMI Z-score, TSF and SSF were directly associated with
Table 3 Adjusted difference (and 95 % confidence interval) in BMI Z-score, triceps (TSF) and subscapular (SSF) skinfold thicknesses by television, video and video game use among Mexican
adolescents from public schools in Morelos, Mexico (1999)
Males Females Males Females Males Females
Television, video and
video games (h/d)
,2 Ref. Ref. Ref. Ref. Ref. Ref. Ref. Ref. Ref. Ref. Ref. Ref.
2–2?9 Difference 0?09 0?04 20?01 20?02 0?98 0?72 20?09 20?34 0?46 0?38 0?22 0?08
95 % CI 20?08, 0?25 20?10, 0?17 20?08, 0?06 20?09, 0?05 20?07, 2?02 20?25, 1?70 20?61, 0?43 20?87, 0?20 20?26, 1?18 20?20, 0?95 20?17, 0?62 20?33, 0?48
3–3?9 Difference 0?16 0?03 0?04 0?02 1?11 0?47 0?68 0?28 0?84 0?26 0?54 0?29
95 % CI 0?03, 0?29 20?09, 0?15 20?03, 0?12 20?06, 0?10 0?31, 1?90 20?40, 1?34 20?05, 1?41 20?46, 1?02 0?21, 1?47 20?36, 0?88 0?05, 1?02 20?29, 0?77
4–4?9 Difference 0?22 0?05 0?08 0?04 1?67 0?93 0?94 0?28 1?20 0?39 0?72 0?33
95 % CI 0?10, 0?33 20?06, 0?15 20?01, 0?18 20?05, 0?14 0?64, 2?70 20?09, 1?95 0?17, 1?71 20?49, 1?06 0?53, 1?87 20?20, 0?98 0?08, 1?35 20?27, 0?94
$5 Difference 0?35 0?13 0?09 0?02 2?01 1?08 1?32 0?35 1?73 0?73 0?85 0?22
95 % CI 0?22, 0?48 0?04, 0?23 0?00, 0?17 20?07, 0?10 1?30, 2?72 0?36, 1?81 0?62, 2?03 20?29, 0?98 1?09, 2?36 0?24, 1?22 0?32, 1?38 20?22, 0?68
Pfor trend ,0?001 0?003 0?026 0?64 ,0?001 0?011 ,0?001 0?14 ,0?001 0?006 0?003 0?45
*Adjusted for age, height, socio-economic status, single-parent family, birth in hospital, parental education level, family income, family health insurance, physical activity, inactivity excluding television, video and video
games, community type, sexual maturity, diagnosis of asthma, dieting and frequency of restaurant dining.
-History of pregnancy and spontaneous abortion also included in females.
Screen time and adiposity in adolescents 1941
time spent viewing television, videos and video games.
The association of screen time with SSF seemed to be
stronger in 11- and 12-year-old males compared with
older youths. Conversely, no overall association of screen
time and anthropometric measures was observed among
Mexican female adolescents. An association between SSF
thickness and screen time was observed in sexually
immature females.
Our results are consistent with previous cross-sectional
and longitudinal findings on television viewing and
increased adiposity and obesity in Mexican and other
. Nevertheless, others have reported
weak or no associations between television viewing and
physical inactivity and adiposity
. Disparate results may
be explained in part by differences in the age distribution of
participants, the cross-sectional nature of some studies and
the use of less comprehensive measures of media use.
Nevertheless, two randomized controlled trials of interven-
tions that reduced television and computer use lend strong
support to a causal relationship between screen time and
increased adiposity in younger children
. Moreover, a
recent analysis on the combined influence of not meeting
the current physical activity and screen time recommenda-
tions of 11 000–13 000 pedometer steps/d and ,2h/dfound
that overweight children were more likely to be non-com-
pliant with these recommendations
There are several indications that screen time plays a
different role within age and sex groups due to differences
<2 2 3 4 5+
Total daily screen time (h)
Adjusted difference in SSF (mm)
Fig. 1 Adjusted difference in subscapular skinfold thickness (SSF, mm) with total daily screen time (h) by age group (—E—,
11–12 years; - - 3- -, 13–14 years; - - m- -, 15–16 years; - - &- -, 17–18 years) in Mexican male adolescents from public schools
in Morelos, Mexico (1999)
<2 2345+
Total daily screen time (h)
Adjusted difference in SSF (mm)
Fig. 2 Adjusted difference in subscapular skinfold thickness (SSF, mm) with total daily screen time (h) by sexual maturity (—E—,
premenarcheal; ——, postmenarcheal) in Mexican female adolescents from public schools in Morelos, Mexico (1999)
1942 M Lajous et al.
in the tempo of physical development. Most studies where
the link between screen time and increased adiposity or
obesity was found included children younger than 10 years
of age
. Studies that did not find the associa-
tion had a mean age closer to 13 years
. In the current
study, age did not appear to modify the association between
screen time and BMI and TSF. However, screen time was
directly associated with SSF among 11- and 12-year-old
males, who may not have undergone sexual maturation. In
line with previous reports
, we observed a null overall
association of screen time with adiposity in female adoles-
cents. However, we explored whether sexual maturity
modified the associations by stratifying on menarcheal
status and observed a significant increasing trend in SSF
thickness in sexually immature females (Pfor interac-
tion 50?053). SSF velocity and distance curves diverge
markedly in males and females during maturation. Results
of these post hoc analyses should be interpreted with
caution. Nevertheless, given null findings in studies with
older adolescents, the association of sedentary behaviour/
inactivity with measures of central fat distribution may be
partially explained by maturity and different maturational
tempos between males and females.
When we evaluated television and videos/video games
independently, we did not find an association with
anthropometric measures of adiposity and obesity.
Nevertheless, videos and video games represent close to
50 % of total screen time in this sample of Mexican ado-
lescents. The association with measures of fat mass and
distribution appeared to be driven by the combined
effects of these three activities, underscoring the impor-
tance of measuring the use of all electronic media.
Mechanisms thought to underlie the relationship between
screen time and adiposity are low energy expenditure due
to the substitution of physical activity by television viewing
and an increase in the consumption of energy-dense foods
advertised on television. Recent data lend stronger support
to energy intake as mediator of the effect of screen time
on adiposity
. A reduction in television viewing and
computer use was reported to significantly reduce daily
energy intake by close to 300 kcal (1255 kJ) over two
years, while no significant increase in physical activity
was observed over the same period
In the current study, we evaluated the association of
screen time and adiposity in a large sample of adolescents
using measures of both fat mass (BMI) and central (SSF)
and peripheral (TSF) fat distribution. We closely captured
recreational inactivity by using a questionnaire validated
in Mexican children
that estimates time spent on tele-
vision, video and video games on weekdays, Saturday
and Sunday. Height, weight, TSF and SSF thickness were
reliably measured with calibrated equipment by trained
personnel using standardized procedures. SSF, a measure
of central fat distribution, rarely has been available in
population-based studies of this magnitude and our
findings provide an interesting insight into its association
with screen time during maturation. Consistency in results
across different anthropometric measures with indepen-
dent measurement errors may further support the pre-
sence of the associations found in the present report.
Our study has some limitations that temper inter-
pretation of findings. First, causal inference is limited by
the cross-sectional design of the study. We hypothesized
that screen time was a determinant of increased adiposity,
but we were unable to assess whether a reverse effect
existed. Prior reports based on longitudinal data support
the directionality of the observed association. Second,
data on screen time and potential confounders are self-
reported, creating a potential for recall bias. However, we
believe that participants in this study population were
unaware that screen time could be a cause of increased
adiposity, so it is unlikely that obese or overweight ado-
lescents would have reported screen time differently from
their leaner counterparts. We are more concerned with
the potential for inaccurate reporting that would attenuate
of the associations. Third, our questionnaire did not
include computer use. At the time the survey was con-
ducted, the contribution of computer use to overall hours
spent in front of a screen was probably very limited in this
population. As in any observational study, our results
may be explained by the influence of unmeasured con-
founders. However, we were able to reduce this possi-
bility by adjusting for numerous socio-economic and
lifestyle variables.
We conclude that screen time is associated with
increased adiposity in Mexican adolescent males. The
association may be partly influenced by maturation;
screen time may be more important in younger adoles-
cents and be more influential in determining central fat
stores, as indicated by SSF. Our results underscore the
importance of understanding modifiable determinants of
adolescent obesity in the context of trends in Mexico. The
high prevalence of obesity and overweight in adolescents
may foreshadow an even greater surge in CVD and
diabetes in Mexico as these adolescents enter young
adulthood. Preventive interventions to promote physical
activity and limit screen time have been explored in
similar populations and were shown to be effective
seen in other populations
, a thorough evaluation of
recommendations on physical activity and screen time in
the Mexican context would be important to support
public policy. Future research should focus on accurately
assessing screen time and physical activity and their
association with adiposity at the national level and on
identifying culturally tailored strategies to modify these
behaviours in Mexican youths.
M.L. was supported by the Mexican National Council for
Science and Technology (CONACyT), the Ministry of
Screen time and adiposity in adolescents 1943
Health of Mexico, the Cabot Family Charitable Trust and the
Epidemiology Department at the Harvard School of Public
Health (HSPH). J.C. was supported by the NIDDK training
grant T32-DK07703 and the HSPH Yerby Postdoctoral
Fellowship Program. The study was partly funded by
Bristol-Myers Squibb Foundation of New York, under the
initiative ‘Better Health for Women: A Global Health Pro-
gram’. Additional funding was provided by CONACyT grant
number 34487-M and the National Institute of Public Health
of Mexico (INSP). Elizabeth Devore participated in the initial
data management. None of the authors had a personal or
financial conflict of interest. Study design and data collec-
tion were performed by E.L.-P., M.H.-A., B.H.-P. and A.C.-V.
E.L.-P was responsible for funding the study. Analysis plan
and manuscript preparation were done by M.L., J.C., K.E.P.
and B.H.-P.
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... 48 Hallazgos parecidos aparecen en el estudio realizado con jóvenes en el estado de Morelos, donde se encontró un IM C 0.13 kg/m 2 mayor en adolescentes varones que pasaban más de cinco horas viendo la televisión, en comparación con los adolescentes que pasaban menos de dos horas diarias viendo la televisión. 49 En análisis de la Ensanut-2006, las horas frente a pantallas o el tiempo dedicado a actividades sedentarias, como ver televisión, jugar videojuegos o usar computadora, se asoció en forma positiva con sobrepeso y obesidad en adolescentes. 52 Asimismo, una vigorosa relación inversa entre actividad física y obesidad fue documentada en adultos del sexo masculino. ...
... Las niñas adolescentes que reportaron estar a dieta para bajar de peso pasaban significativamente menos tiempo frente al monitor que las niñas que querían subir de peso. La media de tiempo frente a la pantalla aumentó significativamente con el nivel de urbanización de la comunidad y, en las niñas, el tiempo frente al monitor aumentó dependiendo del NSE (p <0.01).49 En un estudio realizado con datos de laENN-1999 se encontró que las mujeres de 12 a 49 años de edad dedicaban en promedio 0.45 horas diarias a los deportes y 3.64 horas diarias a ver la televisión. ...
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La obesidad es una enfermedad crónica multifactorial caracterizada por un balance positivo de energía que ocasiona un aumento en los depósitos de grasa corporal y ganancia de peso. La prevalencia de la obesidad en México ha podido estimarse gracias a la información obtenida de diversas encuestas con representatividad nacional. Los resultados presentados en este capítulo provienen de cinco encuestas nacionales realizadas en 1988, 1999, 2000, 2006 y 2012. El uso de metodologías similares de diseño, muestreo y recolección de datos permite la comparación a través del tiempo.
... Although not an issue addressed within this thesis, declines in children's physical activity and a rise in sedentary behaviour in increasingly urbanising LMICs remain a major proximate risk factor for overweight and obesity as physical activity levels decline globally (Lajous et al., 2009). recognise that high levels of television viewing and low levels of physical activity are key risk factors for the development of childhood overweight and obesity. ...
Despite a breadth of research evidencing the association between exclusive breastfeeding and child growth, little is known about infant feeding practices and diet diversity in low- and middle-income countries. In these settings, the weaning transition offers a critical window in which nutritional inputs can help establish the path to lifelong health, yet only one in six young children receives an adequate diet necessary for optimal growth and development. A distinctive nutrition transition in Southeast Asia has coincided with significant economic growth, with the emergence of a double burden of malnutrition. Chronic and persistent undernutrition in young Southeast Asian children is increasingly coupled with rising prevalence of malnutrition, as diets rapidly “westernize” in line with GDP growth and increasing socioeconomic inequalities. This thesis aimed to examine the role of early feeding practices on child nutritional status and growth in light of this nutrition transition, in three economically and culturally diverse Southeast Asian countries (Cambodia, Myanmar and Indonesia). Given the rapid economic and socio-cultural shifts in this region, the role of socioeconomic status on early life feeding practices and dietary diversity is a focus throughout the thesis. Using the most recent DHS data from all three countries, the first analysis in this thesis presents a sub-regional snapshot of the socioeconomic factors associated with exclusive breastfeeding in children aged 0 to <6 months and minimum dietary diversity in children aged 6 to <24 months. The second analysis used structural path analysis to examine the role of continued breastfeeding and dietary diversity in pathways to stunting in Cambodia and how these varied according to contextually relevant, underlying socioeconomic factors. The final analysis in this thesis applied group-based trajectory modelling to longitudinal data from the Indonesian Family Life Survey, to identify BMI growth trajectories and examine early life feeding practices associated with BMI trajectory membership. Overall, evidence from Cambodia, Myanmar and Indonesia demonstrates that exclusive and continued breastfeeding and dietary diversity in young children are clearly defined by socioeconomic conditions. The research presented in this thesis further suggests that feeding practices during the first two years of life play significant mediating roles in the complex pathways between underlying socioeconomic factors and short-term nutritional status in young children, however these associations are harder to identify over longer periods of study, due to the limitations of observational studies. Keywords: Dietary diversity; breastfeeding; Southeast Asia; child nutrition; nutrition transition
... There is an overall sedentary lifestyle among the young students. Sedentary lifestyle can be defined as an action or a movement in which physical inactivity is dominating the physical activity, or in other words, the resulting energy outflow is close to energy in flow or expenditure at rest ( Lajous et al., 2009). Multiple interactions exist between lack of physical activity and obesity; for instance, physical activity is essential to achieve proper energy balance in order to prevent or reverse obesity. ...
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This study examines the attitude of Pakistani students towards sports and physical activities as ratio of sedentary lifestyle is increasing among them. A sample of 384 students having ages between 18-26 years from five different universities of Islamabad, Pakistan was selected for the study. Attitudes were assessed by using self-administered questionnaire namely Student’s Attitude towards Physical Activity (SATPA). Five dimensions of attitudes were measured for data collection namely Health and Fitness, Social Experience, Aesthetic Experience, Ascetic Experience and Pursuit of Vertigo. SPSS and AMOS were used for analysis of data and the relationship between the variables was examined using Structural Equation Modeling (SEM). Overall results of the study showed that students in Pakistan shows favorable attitude towards physical activities and likes to participate in such activities to improve their health. They are aware of benefits related to participating in sports and physical activities. The finding also showed that cricket is most widely played sports among students in Pakistan.
... Boys (10.5 h/day, SD = 3.9, P = 0.000) are spending more time on small screen than girls (9.7 h/day, SD = 3.8, P = 0.000), as found by other authors. [26,27] With using the eating score (EAT-26), 23.56% students were defined as having disordered eating attitudes. Comparing results from other studies which showed the prevalence of disordered eating as US: 22%-26%, Canada: 16%, Japan: 35%, South Africa: 21.2%, Turkey: 45.2%, Singapore: 10.5%. ...
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Aim To Study Relationship of physical activity (PA) with body image, self-esteem, body mass index (BMI), sedentary lifestyle and eating attitude in adolescents. Methods An observational cross-sectional study done at the Centre for Adolescent Health, Kalawati Saran Children Hospital, Lady Hardinge Medical College, New Delhi, India. Volunteering adolescents between the age group of 13 and 18 years were included and assessed using PA questionnaire for adolescents Score, Body Shape Questionnaire-34 Score, Rosenberg self esteem Score, adolescent sedentary activity questionnaire score, eating attitude test (EAT-26) and BMI Z-score. Relationship of these scales to various parameters was assessed using correlation and regression. Results A total of 191 boys and girls were included in the study; 25% had underweight, 75% were normal (only 1 child had overweight and none had obesity). Three fourth (77%) of the children had low PA. The girls were relatively more inactive (83.9% girls vs. 72.1%boys). Most (90.05%) subjects did not have any concerns related to body image. Almost all the subjects had normal or high self esteem. Nearly one quarter of the subjects (23.56%) had disordered eating behaviours. Multiple regression found the PA is positively dependent on EAT 26 score and adolescent sedentary activity questionnaire (ASAQ) score (sedentary score) in girls, whereas in males ASAQ (sedentary score) score was only variable related to physical activity questionnaire for adolescents score (PAQ-A). Conclusion Normal weight and underweight adolescents had minimal PA and despite this, almost all had normal self-esteem and body image. PA was significantly related to eating and sedentary behaviours.
... In LeBlanc et al. 37 , SB was assessed both by questionnaire and accelerometer. In regard to adiposity markers, only four studies not showed Body Mass Index measures 24,38,42,55 (Table 2). ...
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This study reviewed the relationship between sedentary behavior (SB) and body composition in children and adolescents from low-and-mid income countries (LMIC). A systematic review was developed through manual and electronic searches in eight databases. Were included observational studies conducted in LMIC, with children and adolescents from three to 19 years. As results, 39 original articles were found (37 cross-sectional, 1 case-control study and 1 cohort), which in all presented 75 analyzes, most of them based on screen behaviors (n = 71; 94.7%). At all, 15 of 25 analyses showed risk associations between SB and unfavorable body composition. When focusing on the dose of sedentary behavior, risk associations were verified in distinct cutoff points: 1h/d (3 of 3 analyses); 2h/d (9 of 16); 3h/d (2 of 5); 4h/d (4 of 5) and 5h/d (3 of 6). Television time was the SB type most frequently associated as risk in all categories. In conclusion, recognition of these associations is important both to support future studies and for its dissemination in preventive messages in the population of interest. Also, further longitudinal studies are necessary for narrowing the casual relationships between the variables.
... Sedentary behaviour, defined as "any waking behaviour characterised by an energy expenditure ≤ 1.5 metabolic equivalents, while in a sitting, reclining or lying posture" [8], may increase the risk of cardiometabolic disease, such as hypertension and diabetes, in children [5,9,10]. The risk of childhood obesity increases in a dose-response manner as sedentary levels rise [5,11,12]. Excessive screen time (often used as a proxy for sedentary time in children) is also associated with depressive symptoms whereas reduced screen time and increased physical activity levels are linked to emotional stability, higher cognitive function and higher self-esteem in children [5,12,13]. ...
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Children are increasingly spending more time sedentary at school and during leisure time. This study examined the effects of a standing desk intervention in a classroom on children’s standing and sitting time at school, sedentary and physical activity levels throughout the day (waking hours), and musculoskeletal discomfort. A within-subjects crossover study design was used. Participants used either a standing desk or traditional seated desk for 21 days before swapping desks for another 21 days. Accelerometry and musculoskeletal discomfort data were collected during the last seven days of each 21-day period. Mixed models were used to analyse accelerometry data. Zero-inflated regression models and logistic regression models were used to analyse discomfort data. Forty-seven male students (aged 10–11 years) participated in the study. Standing time was 21 min/school day higher (p < 0.001) and sitting time was 24 min/school day lower (p = 0.003) when standing desks were used. No significant differences were found in sedentary and physical activity time during waking hours between the standing desk and seated desk conditions. Students were less likely to report musculoskeletal discomfort in the neck, shoulder, elbows and lower back when using standing desks (OR 0.52–0.74). Standing desks significantly increased classroom standing time and decreased musculoskeletal discomfort reports but had no overall effect on daily physical activity levels. Schools should consider moving towards classrooms enabling a variety of postures to potentially improve the long-term health of children.
... Foods and beverages have become energy dense and high in saturated fats and refined carbohydrates, and these nutrients present cardiovascular risk factors [5][6][7]; meanwhile, consumption of fresh fruits, vegetables, and water has diminished [8]. Conversely, both children and adults have become less physically active and spend more time on sedentary activities [9,10]. ...
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Background: Obesity is a chronic low-intensity state of inflammation with metabolic alterations that, when acquired during childhood, lead to severe illness in adults. Encouraging healthy eating habits and physical activity is the basis for preventing and treating obesity and its complications. Objective: To evaluate how a comprehensive intervention promoting healthy eating habits and physical activities in schools affects children's metabolic biomarkers. Methods: Of four Mexico City primary schools in this study, two groups of children that were recruited at their schools were assigned to a 12-month intervention group (IG) and the other two were assigned to control groups (CGs). The intervention had two components: (1) parents/schoolchildren attended in-person educational sessions promoting healthy eating and physical activity habits, and were provided printed information; and (2) parents were able to seek information through a website, and also received brief weekly mobile phone text messages. Anthropometric measurements and fasting blood samples were taken from both groups of children at baseline and again after 12 months. Results: The study involved 187 children in the IG and 128 in the CG. Regardless of each child's nutritional status at the beginning of the study, the intervention improved metabolic parameters; the IG showed a negative effect on glucose concentrations (-1.83; CI 95% -3.06 to -0.60), low-density lipoprotein-cholesterol (-2.59; CI 95% -5.12 to -0.06), insulin (-0.84; CI 95% -1.31 to -0.37), and homeostasis model to assess the insulin resistance index (HOMA-IR; -0.21; CI 95% -0.32 to -0.09) in comparison to the CG. HOMA-IR improved in children who had higher than baseline body mass index z-scores. Conclusions: Intervention through multiple components that promoted healthier eating and physical activity habits improved the metabolic parameters of the children in the study after one year, regardless of their nutritional status.
... Colombian adolescents spend much more time in front of a screen compared to Danish adolescents. In agreement with our findings, prior research in adolescents from Brazil, Mexico and Kenya has found high levels of sedentary behaviours (Azevedo et al., 2014;Lajous, Chavarro, Peterson, Hernández-Prado, Cruz-Valdéz, Hernández-Avila, & Lazcano-Ponce, 2009;Muthuri et al., 2014). In Kenya, using also the ISCOLE-questionnaire, the high level of PI found in this group was similar to the observed PI level in the Colombian adolescents. ...
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p> BACKGROUND & OBJECTIVES: This study aimed to assess levels of physical activity (PA) and sedentary behaviours among Danish and Colombian adolescents, and to compare relevant environmental and psychosocial factors associated with physical inactivity (PI) between both student groups. Further, we aimed to compare PI between Danish students born in Denmark and those with immigrant background living in Denmark, but born in another country. METHODS: The comparative study was performed with 1.374 Danish adolescents (among them 152 born outside the country) who participated in the Danish Youth Cohort and 452 Colombian students who completed the ISCOLE questionnaire, both from the most disadvantaged socioeconomic strata. RESULTS: The prevalence of physical inactivity (PI) was much higher among Colombian students (74.6%) compared with Danish (25.2%) and with students with a non-Danish background living in Denmark (21.1%). Both groups of Danish adolescents participated more often in organized sports, spent more time on sports after school, were more likely to actively commute to school compared to Colombians and spent less time on screen viewing than Colombians did. In both Columbian and Danish students, low time spent on sports after school, and poorer self-perceived health, were associated with PI. Sedentary behaviours (time in front of screen) were also positively associated with PI. CONCLUSION: Most Colombian adolescents were not meeting the recommendation of accumulating at least 60 minutes per day of moderate-to-vigorous intensity PA for positive health outcomes as most Danish adolescents did independently of their ethnic background. We assume that the physical and social environment in the neighbourhoods where adolescents live may explain the differences in levels of PA between the countries.</p
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Today, the time spent actively is increasingly being replaced by screen-based media, although in some teenagers, a high level of physical activity (PA) and longer time spent in front of a screen (screen time, ST) may coexist as a mixed behavioral pattern. This study aimed to examine the association of the pattern created as activity (low/high ST with high PA) and inactivity patterns (low/high ST with low PA) with overweight, central obesity, and muscle strength in Polish teenagers taking into consideration socioeconomic and demographic factors. Cross-sectional data were collected from elementary school children (n = 1567), aged 11–13 years. Height, weight, waist circumference, and handgrip strength were measured. Body mass index (BMI) was calculated as the overweight measure, and the waist-to-height ratio (WHtR) was calculated as the central obesity measure. Data on ST, PA, socioeconomic status, demographics, and nutrition knowledge were collected by a questionnaire. Activity–inactivity patterns were defined by an a priori approach. Multivariate logistic regression modelling was applied. The most active pattern (lowST-highPA) was found in 17% of the total sample. Teenagers with the most inactive pattern (highST-lowPA) had over four times higher chance of general overweight. No association between WHtR ≥0.5 and highST-highPA pattern was found. Higher muscle strength (>1 SD) was associated only with high physical activity. Urban residence or lower socioeconomic status increased adherence to the most inactive pattern. From a public health perspective, implementing interventions promoting active patterns in 11–13-year-old teenagers is important for obesity prevention and enhanced physical fitness, especially in girls, teenagers living in urban areas, and from families with lower socio-economic status.
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Background: Playing video games, a form of sedentary behaviour, is associated with poor well-being and increased risk of morbidity due to chronic disease. However, the association between health behaviours and video gaming is poorly understood. The purpose of this population-based study was to reveal the differences in dietary habits and physical activity for adolescent men with high amount of video games on weekdays, as compared to their peers who play less often. Methods: Seven hundred ninety-six adolescent men (age: mean = 17.8, SD = 0.6) attended compulsory conscription for military service in 2013 and completed a questionnaire regarding the amount and frequency of their video gaming. They also participated in a medical examination and underwent physiological measurements. The participants who played video games more than 3 h/d on weekdays were compared with those who played 3h/d or less. The association between health behaviours and the amount of playing video gaming was analysed using multivariable logistic regression analysis. Results: 24.1% (n = 192) of the participants reported video gaming in excess of 3 h/d. This group had higher incidence of having low physical fitness, having poor eating habits, and being obese. No differences were found in smoking or alcohol drinking habits. Other factors, including low leisure-time physical activity (OR = 1.94; 95% CI, 1.29-2.91), low consumption of vegetables and fruits (OR = 0.83; 95% CI, 0.72-0.97), high consumption of sweetened soft drinks (OR = 1.28; 95% CI, 1.06-1.55) and high amount of sitting time (OR = 1.40; 95% CI, 1.28-1.52), explained one-fourth of the difference. Conclusion: In this population-based study, adolescent men who played video games a lot on weekdays had lower physical fitness, were more often obese, and had poorer dietary habits, as compared to their peers who played less often. Because playing video games typically adds to a person's total sedentary time, this activity may be associated with adverse health outcomes at a very young age- especially in combination with poor health behaviours. The results of this study can be utilized to promote health interventions targeted at adolescent men so as to raise their awareness of the disadvantages of excessive video gaming.
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Physical inactivity contributes to weight gain in adults, but whether this relationship is true for children of different ethnic groups is not well established. To assess participation in vigorous activity and television watching habits and their relationship to body weight and fatness in US children. Nationally representative cross-sectional survey with an in-person interview and medical examination. SETTING and Between 1988 and 1994, 4063 children aged 8 through 16 years were examined as part of the National Health and Nutrition Examination Survey III. Mexican Americans and non-Hispanic blacks were oversampled to produce reliable estimates for these groups. Episodes of weekly vigorous activity and daily hours of television watched, and their relationship to body mass index and body fatness. Eighty percent of US children reported performing 3 or more bouts of vigorous activity each week. This rate was lower in non-Hispanic black and Mexican American girls (69% and 73%, respectively). Twenty percent of US children participated in 2 or fewer bouts of vigorous activity perweek, and the rate was higher in girls (26%) than in boys (17%). Overall, 26% of US children watched 4 or more hours of television per day and 67% watched at least 2 hours per day. Non-Hispanic black children had the highest rates of watching 4 or more hours of television per day (42%). Boys and girls who watch 4 or more hours of television each day had greater body fat (P<.001) and had a greater body mass index (P<.001) than those who watched less than 2 hours per day. Many US children watch a great deal of television and are inadequately vigorously active. Vigorous activity levels are lowest among girls, non-Hispanic blacks, and Mexican Americans. Intervention strategies to promote lifelong physical activity among US children are needed to stem the adverse health consequences of inactivity.
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OBJETIVO: Evaluar la validez y reproducibilidad de un cuestionario autoaplicado de actividad e inactividad física en escolares de 10 a 14 años de la ciudad de México. MATERIAL Y MÉTODOS: Se desarrolló un cuestionario autoaplicado sobre la actividad e inactividad física que se aplicó dos veces a una muestra de 114 estudiantes, de 10 a 14 años de edad, en una población de bajos y medianos ingresos de la ciudad de México, entre mayo y diciembre de 1996. Las madres de los estudiantes llenaron el mismo cuestionario, mientras que aquéllos completaron dos recordatorios de actividad física de 24 horas, que se usaron como criterio de comparación. Se calcularon medidas de tendencia central y de dispersión y se estimó correlación de Pearson. RESULTADOS: Las correlaciones entre las horas al día dedicadas a la actividad e inactividad física del cuestionario de los estudiantes y las de los recordatorios de 24 horas ajustadas por edad, sexo, zona de residencia y enfermedad anterior a la administración del cuestionario fueron de 0.03 para la actividad moderada, de 0.15 para la actividad vigorosa y de 0.51 (p=0.001) para el tiempo dedicado a ver televisión. Al comparar con los recordatorios de 24 horas, el cuestionario sobrestimó el tiempo de ver televisión, leer o participar en actividades vigorosas, y subestimó el tiempo de actividad moderada. Se observaron coeficientes de reproducibilidad en seis meses aceptables para el tiempo de ver televisión (r=0.53), dormir (r=0.40), actividad moderada (r=0.38) y actividad vigorosa (r=0.55) (p<0.05). CONCLUSIONES: Entre los estudiantes de 10 a 14 años de la ciudad de México, el cuestionario mostró validez aceptable para estimar el tiempo de ver televisión, y una reproducibilidad aceptable de las medidas del tiempo de ver televisión, de la actividad moderada y de la vigorosa.
Objectives To examine the relationship between television watching, energy intake, physical activity, and obesity status in US boys and girls, aged 8 to 16 years.Methods We used a nationally representative cross-sectional survey with an in-person interview and a medical examination, which included measurements of height and weight, daily hours of television watching, weekly participation in physical activity, and a dietary interview. Between 1988 and 1994, the Third National Health and Nutrition Examination Survey collected data on 4069 children. Mexican Americans and non-Hispanic blacks were oversampled to produce reliable estimates for these groups.Results The prevalence of obesity is lowest among children watching 1 or fewer hours of television a day, and highest among those watching 4 or more hours of television a day. Girls engaged in less physical activity and consumed fewer joules per day than boys. A higher percentage of non-Hispanic white boys reported participating in physical activity 5 or more times per week than any other race/ethnic and sex group. Television watching was positively associated with obesity among girls, even after controlling for age, race/ethnicity, family income, weekly physical activity, and energy intake.Conclusions As the prevalence of overweight increases, the need to reduce sedentary behaviors and to promote a more active lifestyle becomes essential. Clinicians and public health interventionists should encourage active lifestyles to balance the energy intake of children.
Background and Methods: The prevalence of obesity among children and adolescents has increased, and television viewing has been suggested as a cause. We examined the relation between hours of television viewed and the prevalence of overweight in 1990, and the incidence and remission of overweight from 1986 to 1990 in a nationally representative cohort of 746 youths aged 10 to 15 years in 1990 whose mothers were 25 to 32 years old. Overweight was defined as a body mass index higher than the 85th percentile for age and gender.Results: We observed a strong dose-response relationship between the prevalence of overweight in 1990 and hours of television viewed. The odds of being overweight were 4.6 (95% confidence interval, 2.2 to 9.6) times greater for youth watching more than 5 hours of television per day compared with those watching for 0 to 2 hours. When adjustments were made for previous overweight (in 1986), baseline maternal overweight, socioeconomic status, household structure, ethnicity, and maternal and child aptitude test scores, results were similar (odds ratio, 5.3; 95% confidence interval, 2.3 to 12.1). We also found significant relations between television viewing and increased incidence and decreased remission of overweight during this 4-year period, adjusted for baseline covariates. The adjusted odds of incidence were 8.3 (95% confidence interval, 2.6 to 26.5) times greater for youth watching more than 5 hours of television per day compared with those watching for 0 to 2 hours. Estimates of attributable risk indicate that more 60% of overweight incidence in this population can be linked to excess television viewing time.Conclusion: Television viewing affects overweight among youth, and reductions in viewing time could help prevent this increasingly common chronic health condition.(Arch Pediatr Adolesc Med. 1996;150:356-362)
Objectives To test whether increased television viewing is associated with increased total energy intake and with increased consumption of foods commonly advertised on television, and to test whether increased consumption of these foods mediates the relationship between television viewing and total energy intake. Design Prospective observational study with baseline (fall 1995) and follow-up (spring 1997) measures of youth diet, physical activity, and television viewing. We used food advertising data to identify 6 food groups for study (sweet baked snacks, candy, fried potatoes, main courses commonly served as fast food, salty snacks, and sugar-sweetened beverages). Setting and Participants Five public schools in 4 communities near Boston. The sample included 548 students (mean age at baseline, 11.70 years; 48.4% female; and 63.5% white). Main Outcome Measures Change in total energy intake and intake of foods commonly advertised on television from baseline to follow-up. Results After adjusting for baseline covariates, each hour increase in television viewing was associated with an additional 167 kcal/d (95% confidence interval, 136-198 kcal/d; P<.001) and with increases in the consumption of foods commonly advertised on television. Including changes in intakes of these foods in regression models provided evidence of their mediating role, diminishing or rendering nonsignificant the associations between change in television viewing and change in total energy intake. Conclusions Increases in television viewing are associated with increased calorie intake among youth. This association is mediated by increasing consumption of calorie-dense low-nutrient foods frequently advertised on television.
Context Some observational studies have found an association between television viewing and child and adolescent adiposity.Objective To assess the effects of reducing television, videotape, and video game use on changes in adiposity, physical activity, and dietary intake.Design Randomized controlled school-based trial conducted from September 1996 to April 1997.Setting Two sociodemographically and scholastically matched public elementary schools in San Jose, Calif.Participants Of 198 third- and fourth-grade students, who were given parental consent to participate, 192 students (mean age, 8.9 years) completed the study.Intervention Children in 1 elementary school received an 18-lesson, 6-month classroom curriculum to reduce television, videotape, and video game use.Main Outcome Measures Changes in measures of height, weight, triceps skinfold thickness, waist and hip circumferences, and cardiorespiratory fitness; self-reported media use, physical activity, and dietary behaviors; and parental report of child and family behaviors. The primary outcome measure was body mass index, calculated as weight in kilograms divided by the square of height in meters.Results Compared with controls, children in the intervention group had statistically significant relative decreases in body mass index (intervention vs control change: 18.38 to 18.67 kg/m2 vs 18.10 to 18.81 kg/m2, respectively; adjusted difference −0.45 kg/m2 [95% confidence interval {CI}, −0.73 to −0.17]; P=.002), triceps skinfold thickness (intervention vs control change: 14.55 to 15.47 mm vs 13.97 to 16.46 mm, respectively; adjusted difference, −1.47 mm [95% CI, −2.41 to −0.54]; P=.002), waist circumference (intervention vs control change: 60.48 to 63.57 cm vs 59.51 to 64.73 cm, respectively; adjusted difference, −2.30 cm [95% CI, −3.27 to −1.33]; P<.001), and waist-to-hip ratio (intervention vs control change: 0.83 to 0.83 vs 0.82 to 0.84, respectively; adjusted difference, −0.02 [95% CI, −0.03 to −0.01]; P<.001). Relative to controls, intervention group changes were accompanied by statistically significant decreases in children's reported television viewing and meals eaten in front of the television. There were no statistically significant differences between groups for changes in high-fat food intake, moderate-to-vigorous physical activity, and cardiorespiratory fitness.Conclusions Reducing television, videotape, and video game use may be a promising, population-based approach to prevent childhood obesity.
Objective To develop an internationally acceptable definition of child overweight and obesity, specifying the measurement, the reference population, and the age and sex specific cut off points. Design International survey of six large nationally representative cross sectional growth studies. Setting Brazil, Great Britain, Hong Kong, the Netherlands, Singapore, and the United States. Subjects 97 876 males and 94 851 females from birth to 25 years of age. Main outcome measure Body mass index (weight/height 2 ). Results For each of the surveys, centile curves were drawn that at age 18 years passed through the widely used cut off points of 25 and 30 kg/m 2 for adult overweight and obesity. The resulting curves were averaged to provide age and sex specific cut off points from 2›18 years. Conclusions The proposed cut off points, which are less arbitrary and more internationally based than current alternatives, should help to provide internationally comparable prevalence rates of overweight and obesity in children.