Katerina Maximova

Do you see what I see? Weight status misperception and exposure to obesity among children and adolescents

Objective:Obesity prevention in childhood is important. However, changing childrens lifestyle behaviors to reduce overweight is a substantial challenge. Accurately perceiving oneself as overweight/obese has been linked to greater motivation to change lifestyle behaviors. Children and adolescents may be less likely to perceive themselves as overweight/obese if they are exposed to overweight/obese people in their immediate environments. This study examined whether youth who are exposed to overweight parents and schoolmates were more likely to misperceive their own weight status.Design:The Quebec Child and Adolescent Health and Social Survey was a provincially representative, school-based survey of children and adolescents conducted between January and May 1999.Subjects:3665 children and adolescents (age 9, n=1267; age 13, n=1186; age 16, n=1212) from 178 schools. Mean body mass index (BMI) was 17.5, 20.6 and 22.2 kg/m2, respectively.Measurements:The misperception score was calculated as the standardized difference between self-perception of weight status (Stunkard Body Rating Scale) and actual BMI (from measured height and weight). Exposure to obesity was based on parent and schoolmate BMI.Results:Overweight and obese youth were significantly more likely to misperceive their weight compared with non-overweight youth (P<0.001). Multilevel modeling indicated that greater parent and schoolmate BMI were significantly associated with greater misperception (underestimation) of weight status among children and adolescents.Conclusion:Children and adolescents who live in environments in which people they see on a daily basis, such as parents and schoolmates, are overweight/obese may develop inaccurate perceptions of what constitutes appropriate weight status. Targeting misperception may facilitate the adoption of healthy lifestyle behaviors and improve the effectiveness of obesity prevention interventions.

Vigorous physical activity and longitudinal associations with cardiometabolic risk factors in youth.

Objective:To examine the longitudinal associations between different physical activity (PA) intensities and cardiometabolic risk factors among a sample of Canadian youth.Methods:The findings are based on a 2-year prospective cohort study in a convenience sample of 315 youth aged 9–15 years at baseline from rural and urban schools in Alberta, Canada. Different intensities (light, moderate and vigorous) of PA were objectively assessed with Actical accelerometers. The main outcome measures were body mass index (BMI) z-score, waist circumference, cardiorespiratory fitness and systolic blood pressure at 2-year-follow-up and conditional BMI z-score velocity. A series of linear regression models were conducted to investigate the associations after adjusting for potential confounders.Results:At follow-up, cardiorespiratory fitness increased (quartile 1 vs quartile 4=43.3 vs 50.2; Ptrend<0.01) and waist circumference decreased (quartile 1 vs quartile 4=79.0 vs 72.6; Ptrend=0.04; boys only) in a dose-response manner across quartiles of baseline vigorous-intensity PA. A similar trend was observed for systolic blood pressure (quartile 1 vs quartile 4=121.8 vs 115.3; Ptrend=0.07; boys only). Compared with quartile 1 of vigorous-intensity PA, BMI z-score at follow-up and conditional BMI z-score velocity were significantly lower in the quartile 2 and 3 (P<0.05). Waist circumference at follow-up also decreased (quartile 1 vs quartile 4=75.3 vs 73.8; Ptrend=0.04) across quartiles of baseline moderate-intensity PA.Conclusions:Time spent in vigorous-intensity PA was associated with several positive health outcomes 2 years later. These findings suggest that high-intensity activities in youth help to reduce the risk for several chronic diseases.

Physical activity intensity and cardiometabolic risk in youth.

OBJECTIVE To determine the association between physical activity (PA) intensities and cardiometabolic risk factors in youth. DESIGN Cross-sectional study using data from the 2008 Healthy Hearts Prospective Cohort Study of Physical Activity and Cardiometabolic Health in Youth. SETTING Rural and urban communities in Alberta, Canada. PARTICIPANTS A convenience sample of 605 youth aged 9 to 17 years. Youth were on average aged 12.1 years, 248 were boys (41%), and 157 were overweight or obese (26%). MAIN EXPOSURE Actical accelerometer-measured PA intensity. MAIN OUTCOMES MEASURES The primary outcome was body mass index (calculated as weight in kilograms divided by height in meters squared) z score. Secondary outcome measures included waist circumference, systolic blood pressure, and cardiorespiratory fitness (maximal oxygen consumption [[Vdot]O2max]). RESULTS Body mass index z score, waist circumference, and systolic blood pressure decreased and [Vdot]O2max increased in a dose-response manner across tertiles of vigorous PA (adjusted P < .001). No significant differences in cardiometabolic risk factors were seen across tertiles of moderate or light PA in multivariable analyses. Achieving more than 7 minutes of vigorous PA daily was associated with a reduced adjusted odds ratio of overweight status (0.56; 95% CI, 0.33-0.95) and elevated systolic blood pressure (0.36; 95% CI, 0.16-0.79). The odds of overweight status and elevated blood pressure decreased with increasing time and intensity of PA. CONCLUSIONS Only vigorous PA was consistently associated with lower levels of waist circumference, body mass index z score, systolic blood pressure, and increased cardiorespiratory fitness in youth. These findings underscore the importance of vigorous PA in guidelines for children and adolescents.

Cohort Profile: The Quebec Adipose and Lifestyle Investigation in Youth Cohort

Departement de pediatrie, Universite de Montreal, Montreal, Quebec, Canada, Centre de recherche du Centre Hospitalier Universitaire (CHU) Sainte-Justine, Montreal, Quebec, Canada, Departement de medecine sociale et preventive, Universite de Montreal, Montreal, Quebec, Canada, Centre de Recherche du Centre Hospitalier de l’Universite de Montreal, Montreal, Quebec, Canada, Division of Kinesiology, Faculty of Medicine, Universite Laval, Quebec, Canada, Departement d’education physique, Universite Laval, Quebec, Canada, Departement de radiologie, CHU Sainte-Justine, Montreal, Quebec, Canada, School of Dietetics and Human Nutrition, McGill University, Montreal, Quebec, Canada, Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada, Department of Psychiatry, McGill University, Montreal, Quebec, Canada, Office of Senior Medical Advisor, First Nations Inuit Health Branch, Health Canada, Vancouver, British-Columbia, Canada, Departement de kinesiologie, Universite de Montreal, Montreal, Quebec, Canada, School of Public Health, University of Alberta, Edmonton, Alberta, Canada, Department of Psychology, Concordia University, Montreal, Quebec, Canada, Epidemiology and Biostatistics Unit, INRS-Institut Armand-Frappier, Laval, Quebec, Canada, Institut universitaire de cardiologie et de pneumologie de Quebec, Faculte de pharmacie, Universite Laval, Quebec, Canada, Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada, McGill University Health Center Research Institute, Montreal, Quebec, Canada and Institut national de sante publique du Quebec, Montreal, Quebec, Canada

Declines in Physical Activity and Higher Systolic Blood Pressure in Adolescence

The authors examined the potential association between changes in the number of moderate-to-vigorous physical activity (MVPA) sessions per week, adiposity, and systolic blood pressure (SBP) during adolescence. SBP and anthropometric factors were assessed biannually (1999/2000, 2002, and 2004) in a cohort of 1,293 Canadian adolescents aged 12-13 years in 1999. Self-reported 7-day recall data on MVPA sessions >or=5 minutes in duration were collected every 3 months over the 5-year period. Estimates of initial level and rate of decline in number of MVPA sessions per week from individual growth models were used as predictors of SBP in linear regression models. A decline of 1 MVPA session per week with each year of age was associated with 0.29-mm Hg and 0.19-mm Hg higher SBPs in girls and boys, respectively, in early adolescence (ages 12.8-15.1 years) and 0.40-mm Hg and 0.18-mm Hg higher SBPs, respectively, in late adolescence (ages 15.2-17.0 years). The associations were not attenuated by changes in body mass index, waist circumference, or skinfold thickness in girls during late adolescence. Although weaker, associations were evident in boys during late adolescence, as well as in both girls and boys during early adolescence. These results support prevention of declines in MVPA during adolescence to prevent higher blood pressure in youth.

A structural equation model relating adiposity, psychosocial indicators of body image and depressive symptoms among adolescents

Objective:Psychosocial factors, including pressure to be thin and body dissatisfaction, have been hypothesized to mediate the relationship between obesity and depression, especially during adolescence when vulnerability to social pressures around body shape and image is heightened. The objective was to test a model of the relationships among adiposity, psychosocial factors and depression in adolescents.Method:In a population-based sample of 1127 boys and 1167 girls aged 13 and 16 years, a model of the relationships between adiposity, pressure to be thin, body dissatisfaction and depressive symptoms was tested using structural equation modeling.Results:Among girls, adiposity accounted for 62% of the total effect of depressive symptoms through its association with pressure to be thin and body dissatisfaction. Pressure to be thin was also uniquely related to depressive symptoms. Among boys, only body dissatisfaction was associated with depressive symptoms.Conclusion:Results support a relationship between adiposity, body satisfaction, pressure to be thin and depressive symptoms. Depressive symptoms should be assessed in obese adolescents, and interventions to prevent and treat obesity should incorporate elements targeting body dissatisfaction.

Ability of different adiposity indicators to identify children with elevated blood pressure.

Objective Body composition measured by dual-energy X-ray absorptiometry (DXA) is believed to be superior to crude measures such as BMI or waist circumference (WC) to assess health risks associated with adiposity in adults. We compared the ability of BMI, WC, waist-to-height ratio (WHtR), percentage body fat from skinfold thickness, and measures of total and central fat assessed by DXA to identify children with elevated blood pressure (BP). Study design The QUALITY Study follows 630 Caucasian families (father, mother, and child originally aged 8–10 years). BP, height, weight, WC, and skinfold thickness were measured according to standardized protocols. Elevated BP was defined as systolic or diastolic BP at least 90th age, sex, and height-specific percentile. Total and central fat were determined with DXA. The area under the receiver operating characteristic (ROC) curve (AUC) statistic was computed from logistic models that adjusted for age, sex, height, Tanner stage, and physical activity. Results All adiposity indicators were highly correlated. WC and WHtR did not show superior ability over BMI to identify children with elevated SBP (P = 0.421 and 0.473). Measures of total and central fat from DXA did not show an improved ability over BMI or WC to identify children with elevated SBP (P = 0.325–0.662). Conclusion Results support the use of BMI in clinical and public health settings, at least in this age group. As all indicators had a limited ability to identify children with elevated BP, results also support measurement of BP in all children of this age independent of a weight status.

The importance of Active Transportation to and from school for daily physical activity among children.

OBJECTIVE To investigate if students who use of Active Transportation (AT) to and from school among urban and rural Canadian children are more likely to meet physical activity recommendations. METHODS The Raising healthy Eating and Active Living in Alberta (REAL Kids Alberta) study is a population-based health survey among Grade 5 students. In 2009, physical activity levels were measured using time-stamped pedometers (number of steps/hour) among 688 children. Parents reported mode of transportation to and from school (AT/non-AT). Multilevel multiple linear regression analyses with corresponding β coefficients were conducted to quantify the relationship between mode of transportation to and from school with (1) overall step count, and (2) the likelihood of achieving at least 13,500 steps per day recommended for optimal growth and development. RESULTS Among urban children, those who used AT to and from school accumulated more steps [β=1124(95% CI=170,2077)] and although not significant, were more likely to achieve the recommended 13,500 steps/day compared to those not using AT to and from school [OR=1.61(95% CI=0.93,2.81)]. CONCLUSION Using AT to and from school appears to be beneficial to children by supplementing their physical activity, particularly those living in urban regions. Strategies to promote physical activity are needed, particular for children residing in rural regions and smaller towns.

School-Based Health Promotion and Physical Activity During and After School Hours

OBJECTIVES: Comprehensive school health (CSH) is a multifaceted approach to health promotion. A key objective of CSH is to foster positive health behaviors outside of school. This study examined the 2-year change in physical activity during and after school among students participating in a CSH intervention in Edmonton, Alberta, Canada. METHODS: This was a quasi-experimental, pre–post trial with a parallel, nonequivalent control group. Intervention schools had to be located in socioeconomically disadvantaged neighborhoods. In the spring of 2009 and 2011, pedometer recordings (7 full days) and demographic data were collected from cross-sectional samples of fifth grade students from 10 intervention schools and 20 comparison schools. A total of 1157 students participated in the study. Analyses were adjusted for potential confounders and the clustered design. RESULTS: Relative to 2009, children in 2011 were more active on schools days (1172 steps per day; P < .001) and on weekends (1450 steps per day; P < .001). However, the increase in mean steps between 2009 and 2011 was greater in CSH intervention schools than in comparison schools (school days: 1221 steps per day; P = .009; weekends: 2001 steps per day; P = .005). These increases remained significant after adjusting for gender and overweight status. CONCLUSIONS: These findings provide evidence of the effectiveness of CSH to affect children’s physical activity during and outside of school. Results of this study justify broader implementation of effective CSH interventions for physical activity promotion and obesity prevention in the long term.

The importance of parental beliefs and support for pedometer-measured physical activity on school days and weekend days among Canadian children

BackgroundParental influences are essential to the behaviours and physical activity of their children. Our study aimed to determine if parental beliefs and support are associated with children’s pedometer measured physical activity levels on school days and weekend days.MethodsIn the spring of 2009 and 2011, we analyzed cross-sectional data from 1,355 grade five students and parents in 30 schools in Alberta, Canada. Parents reported how much they care about exercising, how much they encourage their child to be physically active, and how frequently they engage in physical activities with their child. Physical activity was assessed from step counts obtained from time-stamped pedometers collected over nine consecutive days.ResultsIncreased parental encouragement was positively associated with boys’ and girls’ physical activity on school days (Boys: beta = 1373, 95% CI: 606, 2139; Girls: beta = 632, 95% CI: 108, 1155) and girls’ physical activity on weekend days (beta = 997, 95% CI: 130, 1864). Increased parental care was positively associated with boys’ physical activity on weekend days (beta = 1381, 95% CI: 85, 2676). Increased parental support and engagement was associated with an additional 632–1381 steps/day for children in this study.ConclusionsParental care, encouragement and engagement are associated with physical activity levels of children 10–11 years of age. Policy makers and researchers should consider the importance of targeting parents when designing strategies to promote physical activity in children. This is particularly relevant to weekends and holidays when children’s activity levels are low.