Rumen-protected methionine during heat stress alters mTOR, insulin signaling, and 1-carbon metabolism protein abundance in liver, and whole-blood transsulfuration pathway genes in Holstein cows.

We investigated effects of rumen-protected Met (RPM) during a heat stress (HS) challenge on (1) hepatic abundance of mTOR, insulin, and antioxidant signaling proteins, (2) enzymes in 1-carbon metabolism, and (3) innate immunity. Holstein cows (n = 32; mean ± standard deviation, 184 ± 59 d in milk) were randomly assigned to 1 of 2 environmental groups, and 1 of 2 diets [total mixed ration (TMR) with RPM (Smartamine M; 0.105% dry matter as top-dress) or TMR without (CON); n = 16/diet] in a split-plot crossover design. There were 2 periods with 2 phases. During phase 1 (9 d), all cows were in thermoneutral conditions (TN; temperature-humidity index = 60 ± 3) and fed ad libitum. During phase 2 (9 d), half the cows (n = 8/diet) were exposed to HS using electric heat blankets. The other half (n = 8/diet) remained in TN, but was pair-fed to HS counterparts. After a 14-d washout and 7-d adaptation period, the study was repeated (period 2) and environmental treatments were inverted relative to phase 2, but dietary treatments were the same. Blood was collected on d 6 of each phase 2 to measure immune function and isolate whole-blood RNA. Liver biopsies were performed at the end of each period for cystathione ß-synthase (CBS) and methionine adenosyltransferase activity, glutathione concentration, and protein abundance. Data were analyzed using PROC MIXED in SAS. Abundance of CUL3, inhibitor of antioxidant responses, tended to be downregulated by HS suggesting increased oxidative stress. Heat-shock protein 70 abundance was upregulated by HS. Phosphorylated mTOR abundance was greater overall with RPM, suggesting an increase in pathway activity. An environment × diet (E × D) effect was observed for protein kinase B (AKT), whereas there was a tendency for an interaction for phosphorylated AKT. Abundance of AKT was upregulated in CON cows during HS versus TN, this was not observed in RPM cows. For phosphorylated AKT, tissue from HS cows fed CON had greater abundance compared with all other treatments. The same effect was observed for EIF2A (translation initiation) and SLC2A4 (insulin-induced glucose uptake). An E × D effect was observed for INSR due to upregulation in CON cows during HS versus TN cows fed CON or RPM. There was an E × D effect for CBS, with lower activity in RPM versus CON cows during HS. The CON cows tended to have greater CBS during HS versus TN. An E × D effect was observed for methionine adenosyltransferase, with lower activity in RPM versus CON during HS. Although activity increased in CON during HS versus TN, RPM cows tended to have greater activity during TN. Neutrophil and monocyte oxidative burst and monocyte phagocytosis decreased with HS. An (E × D) effect was observed for whole-blood mRNA abundance of CBS, SOD1 and CSAD; RPM led to upregulation during TN versus HS. Regardless of diet, CDO1, CTH, and SOD1 decreased with HS. Although HS increased hepatic HSP70 and seemed to alter antioxidant signaling, feeding RPM may help cows maintain homeostasis in mTOR, insulin signaling, and 1-carbon metabolism. Feeding RPM also may help maintain whole-blood antioxidant response during HS, which is an important aspect of innate immune function.

Effects of rumen-protected methionine on lactation performance and physiological variables during a heat stress challenge in lactating Holstein cows.

Milk yield, content, and composition are altered by heat stress. Thirty-two multiparous, lactating Holstein cows [balanced by days in milk (mean ± standard deviation; 184 ± 59); body surface area (5.84 ± 0.34 m2)] were randomly assigned to 1 of 2 dietary treatments [total mixed ration with rumen-protected Met (RPM; Smartamine M; Adisseo Inc., Antony, France; 1.05 g of RPM/kg of dry matter intake) or total mixed ration without RPM (CON)], and within each dietary treatment group cows were randomly assigned to 1 of 2 environmental treatment groups in a split-plot crossover design. The study was divided into 2 periods with 2 phases per period. In phase 1 (9 d), all cows were in thermoneutral conditions and fed ad libitum. In phase 2 (9 d), group 1 (n = 16) was exposed to a heat stress challenge (HSC) using electric heat blankets. Group 2 (n = 16) remained in thermoneutral conditions but was pair-fed (PFTN) to HSC counterparts. After a 21-d washout period, the study was repeated (period 2) and the environmental treatments were inverted relative to treatments from phase 2 of period 1, whereas dietary treatments (RPM or CON) remained the same for each cow. Cows were milked 3× per day and samples were taken on d 1, 5, and 9 of each phase. Vaginal temperature was measured every 10 min, rectal temperature and skin temperature were measured 3× per day, and respiration rate and heart rate were recorded once per day. Cow activity was measured using an accelerometer. Paired difference values were calculated for each cow for each period based on the difference between phase 1 baseline means and phase 2 values for each variable. Cows in HSC had a greater increase in vaginal temperature and respiration rate (+0.2°C and +13.7 breaths/min, respectively) compared with cows in PFTN (0.0°C and -1.6 breaths/min, respectively). Cows in PFTN had a greater decrease in dry matter intake and milk yield (-3.9 and -2.6 kg/d, respectively) compared with cows in HSC (-3.2 and -0.9 kg/d, respectively). Cows in CON had a greater decrease in milk protein concentration for PFTN (-0.10 percentage units) and HSC (-0.06 percentage units) compared with cows in RPM for PFTN (0.00 percentage units) and HSC (-0.02 percentage units). Cows in CON for HSC had greater decrease in milk fat concentration compared with cows in RPM for HSC (-0.10 and +0.12 percentage units, respectively). In conclusion, HSC altered physiological and production parameters of cows. Additionally, RPM helped maintain milk protein and fat concentration during HSC, whereas dry matter intake, milk yield, and feed efficiencies were not affected by RPM.

Aluminosilicate clay improves production responses and reduces inflammation during an aflatoxin challenge in lactating Holstein cows.

Mitigation strategies are vital in minimizing the health and economic risks associated with dairy cattle exposure to aflatoxin (AF). The objective of this study was to determine the effects of a commercially available aluminosilicate clay in a lactation diet on production responses, blood chemistry, and liver inflammatory markers of multiparous lactating Holstein cows during an AF challenge. Sixteen multiparous lactating Holstein cows [body weight (mean ± SD) = 758 ± 76 kg; days in milk = 157 ± 43 d] were assigned to 1 of 4 treatments in a replicated 4 × 4 Latin square design with 21-d periods: no adsorbent and no AF challenge (CON), no adsorbent and an AF challenge (POS), 113 g of aluminosilicate clay top-dressed on the total mixed ration (adsorbent; FloMatrix, PMI Nutritional Additives, Arden Hills, MN) with an AF challenge (F4), or 227 g of adsorbent with an AF challenge (F8). The challenge consisted of 100 µg of AFB1/kg of dietary dry matter intake administered orally. For each period, milk was sampled 3× daily from d 14 to 21; blood, feces, and urine were sampled on d 14, 18, and 21; and liver samples were taken on d 18. Liver tissue was assessed for gene expression and histological hepatocyte inflammation. Statistical analysis was preformed using the MIXED and GLIMMIX procedures of SAS (SAS Institute Inc., Cary, NC). Fat-corrected milk (POS = 37.2, F4 = 39.2, and F8 = 38.9 kg/d) increased as concentration of adsorbent in the diet increased. There was a decrease in milk AFM1 concentration at d 18 as concentration of adsorbent in the diet increased (POS = 0.33, F4 = 0.32, and F8 = 0.27 µg/kg). There was a decrease in AFM1 concentration in urine (POS = 2.10, F4 = 1.89, and F8 = 1.78 µg/kg) and AFB1 concentration in feces (POS = 4.68, F4 = 3.44, and F8 = 3.17 µg/kg) as concentration of adsorbent in the diet increased. Cows in CON had greater concentrations of serum cholesterol (202 mg/dL) and plasma superoxide dismutase (2.8 U/mL) compared with cows in POS (196 mg/dL and 2.6 U/mL, respectively). Plasma glutamate dehydrogenase increased as concentration of adsorbent in the diet increased (POS = 37.8, F4 = 39.3, and F8 = 39.1 U/L). The expression of NFKB1 was greater in the liver of cows in POS (0.78) compared with cows in CON (0.70). The expression of MTOR was greater in the liver of cows in CON (1.19) compared with cows in POS (0.96). When compared with cows in CON, cows in POS had greater odds ratio for hepatocyte inflammation (odds ratio = 5.14). In conclusion, the adsorbent used in this study had a positive effect on milk production and hepatocyte inflammation and reduced AF transfer.

Methionine and choline supply alter transmethylation, transsulfuration, and cytidine 5'-diphosphocholine pathways to different extents in isolated primary liver cells from dairy cows.

Insufficient supply of Met and choline (Chol) around parturition could compromise hepatic metabolism and milk protein synthesis in dairy cows. Mechanistic responses associated with supply of Met or Chol in primary liver cells enriched with hepatocytes (PHEP) from cows have not been thoroughly ascertained. Objectives were to isolate and culture PHEP to examine abundance of genes and proteins related to transmethylation, transsulfuration, and cytidine 5'-diphosphocholine (CDP-choline) pathways in response to Met or Chol. The PHEP were isolated from liver biopsies of Holstein cows (160 d in lactation). More than 90% of isolated cells stained positively for the hepatocyte marker cytokeratin 18. Cytochrome P450 (CYP1A1) mRNA abundance was only detectable in the PHEP and liver tissue compared with mammary tissue. Furthermore, in response to exogenous Met (80 µM vs. control) PHEP secreted greater amounts of albumin and urea. Subsequently, PHEP were cultured with Met (40 µM) or Chol (80 mg/dL) for 24 h. Compared with control or Chol, mRNA and protein abundance of methionine adenosyltransferase 1A (MAT1A) and phosphatidylethanolamine methyltransferase (PEMT) were greater in PHEP treated with Met. The mRNA abundance of S-adenosylhomocysteine hydrolase (SAHH), betaine-homocysteine methyltransferase (BHMT), and sarcosine dehydrogenase (SARDH) was greater in Met-treated PHEP compared with control or Chol. Compared with control, greater expression of 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), betaine aldehyde dehydrogenase (BADH), and choline dehydrogenase (CHDH) was observed in cells supplemented with Met and Chol. However, Chol led to the greatest mRNA abundance of CHDH. Abundance of choline kinase α (CHKA), choline kinase ß (CHKB), phosphate cytidylyltransferase 1 α (PCYT1A), and choline/ethanolamine phosphotransferase 1 (CEPT1) in the CDP-choline pathway was greater in PHEP treated with Chol compared with control or Met. In the transsulfuration pathway, mRNA and protein abundance of cystathionine ß-synthase (CBS) was greater in PHEP treated with Met compared with control or Chol. Similarly, abundance of cysteine sulfinic acid decarboxylase (CSAD), glutamate-cysteine ligase, catalytic subunit (GCLC), and glutathione reductase (GSR) was greater in response to Met compared with control or Chol. Overall, these findings suggest that transmethylation and transsulfuration in dairy cow primary liver cells are more responsive to Met supply, whereas the CDP-choline pathway is more responsive to Chol supply. The relevance of these data in vivo merit further study.

The prevalence of community programmes and policies to prevent childhood obesity in a diverse sample of US communities: the Healthy Communities Study.

INTRODUCTION: This manuscript describes the prevalence and attributes of community programmes and policies (CPPs) to address childhood obesity documented as occurring in 130 diverse US communities. METHODS: Key informant interviews (N = 1420) and document abstraction were used to identify and characterize CPPs to promote physical activity and healthy nutrition occurring during a 10-year retrospective study period. Data were collected in 2013-2015 and analysed in 2016. RESULTS: Across all 130 communities, 9681 distinct CPPs were reported as occurring by key informants. Of these, 5574 (58%) focused on increasing physical activity, 2596 (27%) on improving nutrition and 1511 (16%) on both behaviours. The mean number of CPPs per community was 74.0, with a range of 25 to 295 across all communities. Most CPPs occurred more than once (63%) and on average lasted 6.1 years. The greatest number of reported CPPs occurred in school settings (44%). CONCLUSIONS: Communities showed a wide range of investment in the amount of CPPs occurring in settings that affect opportunities for children to engage in physical activity and healthy nutrition. The pattern of implementation of CPPs showed variation over time, with an increase in more recent years. This observational study provides new and valuable information about what US communities are doing to prevent childhood obesity.

Injectable trace minerals (selenium, copper, zinc, and manganese) alleviate inflammation and oxidative stress during an aflatoxin challenge in lactating multiparous Holstein cows.

Trace minerals are vital in the antioxidant response during oxidative stress; however, limited research is available on the effects of trace mineral supplementation during an aflatoxin (AF) challenge. The objective of the study was to determine the effects of 2 subcutaneous injections of 15 mg/mL of Cu, 5 mg/mL of Se, 60 mg/mL of Zn, and 10 mg/mL of Mn (Multimin 90, Multimin North America, Fort Collins, CO) given at 1 mL/90.7 kg of average body weight in response to an AF challenge. Fifty-eight Holstein cows [body weight (mean ± SD) = 734 ± 6 0kg; days in milk = 191 ± 93] were assigned to 1 of 3 treatments in a randomized complete block design. The experimental period (63 d) was divided into an adaptation phase (d 1-56) and a measurement phase (d 57-63). From d 57 to 59, cows received an AF challenge that consisted of 100 µg of aflatoxin B1/kg of dietary dry matter intake (DMI) administered orally via balling gun. Treatments were saline injection and no AF challenge (NEG), saline injection and AF challenge (POS), and trace mineral injection and AF challenge (MM). Injections were performed subcutaneously on d 1 and 29. Milk was sampled 3 times daily from d 56 to 63, blood was sampled on d 0, 56, 60, and 63, and liver samples were taken on d 0 and 60. Two treatment orthogonal contrasts [CONT1 (NEG vs. POS) and CONT2 (POS vs. MM)] were made. Cows in NEG had lower AF excretion in milk and greater 3.5% fat-corrected milk (32.1 ± 1.37 kg/d) compared with cows in POS (28.6 ± 1.43 kg/d). Feed efficiencies (3.5% fat-corrected milk/DMI, energy-corrected milk/DMI, and milk/DMI) were greater for cows in NEG (1.42 ± 0.07, 1.46 ± 0.07, and 1.45 ± 0.07, respectively) than cows in POS (1.16 ± 0.08, 1.18 ± 0.08, and 1.22 ± 0.07, respectively). Cows in POS had greater milk urea nitrogen and blood urea nitrogen than cows in MM. Liver concentrations of Se and Fe were greater for cows in MM compared with cows in POS. Cows in MM tended to have greater plasma glutathione peroxidase activity compared with cows in POS. An upregulation of liver GPX1 was observed for cows in POS compared with cows in MM. In conclusion, subcutaneous injection of trace minerals maintained an adequate antioxidant response when an AF challenge was present.

Relationship of objective street quality attributes with youth physical activity: findings from the Healthy Communities Study.

BACKGROUND: Residential environments may significantly influence youth physical activity (PA). However, few studies have examined detailed street quality attributes via observational audits in relation to context-specific PA among youth. OBJECTIVES: The objective of this study was to explore whether the overall quality of street environments, as well as specific attributes, was associated with neighbourhood-based and street-based PA within a national sample of youth in the Healthy Communities Study. METHODS: Data were collected from 4616 youth from 130 communities across the USA. Youth PA in the neighbourhood and on the participant's street was captured using 7-d recall interviews. Windshield survey observational audits documented five street quality variables: burned, boarded up or abandoned residential units, litter, overall condition of residences, street type and presence of sidewalks in good condition. RESULTS: Youth with no litter on their street reported significantly lower neighbourhood-based PA and youth living on a side street, cul-de-sac, dead-end or one-way street reported greater neighbourhood-based PA. No significant associations were detected for the overall street quality index or with street-based PA. CONCLUSIONS: Specific street quality attributes may be associated with youth PA. Further research and collaboration between diverse disciplines and agencies should focus on understanding and improving street quality to promote youth PA and health.

Associations between community programmes and policies and children's physical activity: the Healthy Communities Study.

BACKGROUND: Community initiatives to promote physical activity in children are common, but evidence supporting their effectiveness is limited. OBJECTIVES: The objective of this study is to examine the relationships between community programmes and policies and children's physical activity in a large and diverse sample of US communities. METHODS: Programmes and policies to promote children's physical activity were assessed in 130 communities by key informant interviews, and physical activity behaviours were measured by self-report and parental report in samples of children in each community (total n = 5138). Associations between composite indices of community programmes and policies and indicators of total and moderate-to-vigorous physical activity were examined without and with adjustment for demographic factors. RESULTS: An index reflecting the 6-year history of the number of behaviour change strategies used in community programmes and policies was positively associated with children's moderate-to-vigorous physical activity. This association was attenuated with adjustment for demographic factors. Effect modification analyses found that the association was positive among non-Hispanic children but was negative for Hispanic children. CONCLUSIONS: Community initiatives to promote physical activity in children were positively associated with children's physical activity in non-Hispanic children. Such initiatives were negatively associated with physical activity in Hispanic children, suggesting that future research should consider unique cultural factors when designing community initiatives to promote activity in this population sub-group.

Regional comparisons of walking or bicycling for fun or exercise and for active transport in a nationally distributed sample of community-based youth.

BACKGROUND: Physical activity helps prevent excessive weight gain in youth. Few studies have examined regional variations in common activities, walking and bicycling. OBJECTIVE: The primary aim was to examine participation in previous 7-day walking/bicycling for active transport and for fun/exercise by region, gender and age groups. METHODS: Children (n = 2693) from 130 diverse, geographically distributed US communities reported participation in previous 7-day walking/bicycling. Mixed model ANOVAs were used to compare walking/bicycling by region, gender and age groups using Healthy Communities Study data. RESULTS: Walking/bicycling for fun/exercise was higher in the Midwest, South and West compared with the Northeast, with the same regional patterns for boys, girls and 9-11-year olds. Walking/bicycling to non-school destinations was higher in the Midwest compared with the South and Northeast, with the same pattern for girls and 9-11-year olds. Walking/bicycling to school was higher Midwest, Northeast and West compared with the South, with similar patterns for girls and 12-15-year olds. CONCLUSIONS: Walking/bicycling for fun/exercise and to non-school destinations had higher prevalence than active transport to school. The Northeast reported lower walking/bicycling for fun/exercise; the South and Northeast reported lower walking/bicycling to non-school destinations. Program/policy initiatives should consider contextual demographic influences, as well as purpose/destination of walking/bicycling.

The longitudinal relationship between community programmes and policies to prevent childhood obesity and BMI in children: the Healthy Communities Study.

BACKGROUND: Although a national epidemic of childhood obesity is apparent, how community-based programmes and policies (CPPs) affect this outcome is not well understood. OBJECTIVES: This study examined the longitudinal relationship between the intensity of CPPs in 130 communities over 10 years and body mass index (BMI) of resident children. We also examined whether these relationships differ by key family or community characteristics. METHODS: Five thousand one hundred thirty-eight children in grades K-8 were recruited through 436 schools located within 130 diverse US communities. Measures of height, weight, nutrition, physical activity and behavioural and demographic family characteristics were obtained during in-home visits. A subsample of families consented to medical record review; these weight and height measures were used to calculate BMI over time for 3227 children. A total of 9681 CPPs were reported during structured interviews of 1421 community key informants, and used to calculate a time series of CPP intensity scores within each community over the previous decade. Linear mixed effect models were used to assess longitudinal relationships between childhood BMI and CPP intensity. RESULTS: An average BMI difference of 1.4 kg/m2 (p-value < 0.01) was observed between communities with the highest and lowest observed CPP intensity scores, after adjusting for community and child level covariates. BMI/CPP relationships differed significantly by child grade, race/ethnicity, family income and parental education; as well as community-level race/ethnicity. CONCLUSIONS: These results indicate that, over time, more intense CPP interventions are related to lower childhood BMI, and that there are disparities in this association by sociodemographic characteristics of families and communities.

Physical activity and osteoarthritis: a consensus study to harmonise self-reporting methods of physical activity across international cohorts.

Physical activity (PA) is increasingly recognised as an important factor within studies of osteoarthritis (OA). However, subjective methods used to assess PA are highly variable and have not been developed for use within studies of OA, which creates difficulties when comparing and interpreting PA data in OA research. The aim of this study was, therefore, to gain expert agreement on the appropriate methods to harmonise PA data among existing population cohorts to enable the investigation of the association of PA and OA. The definition of PA in an OA context and methods of harmonization were established via an international expert consensus meeting and modified Delphi exercise using a geographically diverse committee selected on the basis of individual expertise in physical activity, exercise medicine, and OA. Agreement was met for all aims of study: (1) The use of Metabolic Equivalent of Task (MET) minutes per week (MET-min/week) as a method for harmonising PA variables among cohorts; (2) The determination of methods for treating missing components of MET-min/week calculation; a value will be produced from comparable activities within a representative cohort; (3) Exclusion of the domain of occupation from total MET-min/week; (4) The need for a specific measure of joint loading of an activity in addition to intensity and time, in studies of diseases, such as OA. This study has developed a systematic method to classify and harmonise PA in existing OA cohorts. It also provides minimum requirements for future studies intending to include subjective PA measures.

The 3-year evolution of a preschool physical activity intervention through a collaborative partnership between research interventionists and preschool teachers.

Despite evidence that preschoolers spend the majority of their time in sedentary activities, few physical activity interventions have focused on preschool-age children. Health promotion interventions that can be integrated into the daily routines of a school or other setting are more likely to be implemented. The Study of Health and Activity in Preschool Environments employed a flexible approach to increasing physical activity opportunities in preschools' daily schedules through recess, indoor physical activity and physical activity integrated into academic lessons. Eight preschools were randomly assigned to receive the study's physical activity intervention. Teachers in these schools partnered with university-based interventionists across 3 years to design and implement a flexible and adaptive intervention. The intervention approach included trainings and workshops, site visits and feedback from intervention personnel, newsletters, and physical activity equipment and materials. Teachers reported a high acceptability of the intervention. The purpose of this article is to describe the evolution of a multi-component physical activity intervention in preschools, including (i) a description of the intervention components, (ii) an explanation of the intervention process and approach, and (iii) a report of teachers' perceptions of barriers to implementation.

Factors associated with development of excessive fatness in children and adolescents: a review of prospective studies.

The purpose of this review was to examine the factors that predict the development of excessive fatness in children and adolescents. Medline, Web of Science and PubMed were searched to identify prospective cohort studies that evaluated the association between several variables (e.g. physical activity, sedentary behaviour, dietary intake and genetic, physiological, social cognitive, family and peer, school and community factors) and the development of excessive fatness in children and adolescents (5-18 years). Sixty-one studies met the eligibility criteria and were included. There is evidence to support the association between genetic factors and low physical activity with excessive fatness in children and adolescents. Current studies yielded mixed evidence for the contribution of sedentary behaviour, dietary intake, physiological biomarkers, family factors and the community physical activity environment. No conclusions could be drawn about social cognitive factors, peer factors, school nutrition and physical activity environments, and the community nutrition environment. There is a dearth of longitudinal evidence that examines specific factors contributing to the development of excessive fatness in childhood and adolescence. Given that childhood obesity is a worldwide public health concern, the field can benefit from large-scale, long-term prospective studies that use state-of-the-art measures in a diverse sample of children and adolescents.

Moderate-to-vigorous physical activity is associated with decreases in body mass index from ages 9 to 15 years.

OBJECTIVE: The purpose of this study is to determine whether time spent in objectively measured physical activity is associated with change in body mass index (BMI) from ages 9 to 15. DESIGN AND METHODS: The participants were enrolled in the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development (n = 938). At ages 9, 11, 12, and 15 the time spent in moderate-to-vigorous physical activity (MVPA) was objectively measured, and BMI was calculated (kg/m(2) ). Longitudinal quantile regression was used to analyze the data. The 10th, 25th, 50th, 75th, and 90th BMI percentiles were modeled as the dependent variables with age and MVPA (h/day) modeled as predictors. Adjustment was also made for gender, race, sleep, healthy eating score, maternal education, and sedentary behavior. RESULTS: A negative association between MVPA and change in BMI was observed at the 90th BMI percentile (-3.57, 95% CI -5.15 to -1.99 kg/m(2) per hour of MVPA). The negative association between time spent in MVPA and change in BMI was progressively weaker toward the 10th BMI percentile (-0.27, 95% CI -0.62 to 0.07 kg/m(2) per hour of MVPA). The associations remained similar after adjusting for the covariates, and when the analyses were stratified by gender. CONCLUSION: Time spent in MVPA was negatively associated with change in BMI from age 9 to 15. The association was strongest at the upper tail of the BMI distribution, and increasing time spent in MVPA could help reduce the prevalence of childhood obesity.

Association between objectively measured sedentary behavior and body mass index in preschool children.

OBJECTIVE: To determine the association between accelerometry-derived sedentary behavior and body mass index (BMI) z-score in preschool children, and to determine whether the association changed when applying three different accelerometry cutpoints for sedentary behavior. DESIGN AND SUBJECTS: Cross-sectional design. Data came from two completed studies: Children's Activity and Movement in Preschool Study (CHAMPS) and the Environmental Determinants of Physical Activity in Preschool Children (EDPAPC) study. Children of ages 3-5 years with complete data on sedentary behavior, BMI z-score, physical activity and other covariates were included in the analyses (N=263 in CHAMPS and N=155 in EDPAPC). Accelerometry data were summarized as time spent in sedentary behavior (min h(-1)) using three different cutpoints developed specifically for preschool children (<37.5, <200 and <373 counts per 15 s). Linear mixed regression models were used to determine the association between time spent in sedentary behavior and BMI z-score; age, gender, race, parental education, preschools and moderate-to-vigorous physical activity (MVPA) were included as covariates. RESULTS: In both CHAMPS and EDPAPC studies, no independent association between time spent in sedentary behavior and BMI z-score was observed after adjusting for MVPA. The observed null association between sedentary behavior and BMI z-score was maintained even with different sedentary behavior cutpoints. CONCLUSIONS: Regardless of cutpoints used, accelerometry-derived sedentary behavior was not independently associated with BMI z-score in two independent samples of preschool children. Longitudinal studies addressing this research question are needed.

Time spent in sedentary behavior and changes in childhood BMI: a longitudinal study from ages 9 to 15 years.

OBJECTIVE: To determine if time spent in objectively measured sedentary behavior is associated with a change in body mass index (BMI) between ages 9 and 15 years, adjusting for moderate-to-vigorous physical activity (MVPA). DESIGN: Prospective observational study of children at ages 9 (2000), 11 (2002), 12 (2003) and 15 years (2006). Longitudinal quantile regression was used to model the influence of predictors on changes at the 10th, 25th, 50th, 75th and 90th BMI percentiles over time. SUBJECTS: Participants were enrolled in the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development and include both boys and girls (n=789). MEASUREMENTS: Objectively measured BMI (kg m(-2)) was the outcome variable and objectively measured sedentary behavior was the main predictor. Adjustment was also made for MVPA, gender, race, maternal education, hours of sleep and healthy eating index. RESULTS: Increases in BMI were observed at all percentiles, with the greatest increase observed at the 90th BMI percentile. Spending more time in sedentary behavior (h per day) was associated with additional increases in BMI at the 90th, 75th and 50th BMI percentiles, independent of MVPA and the other covariates (90th percentile=0.59, 95% confidence interval (95% CI): 0.19-0.98 kg m(-2); 75th percentile=0.48, 95% CI: 0.25-0.72 kg m(-2); and 50th percentile=0.19, 95% CI: 0.05-0.33 kg m(-2)). No associations were observed between sedentary behavior and changes at the 25th and 10th BMI percentiles. CONCLUSION: Sedentary behavior was associated with greater increases in BMI at the 90th, 75th and 50th BMI percentiles between ages 9 and 15 years, independent of MVPA. Preventing an increase in sedentary behavior from childhood to adolescence may contribute to reducing the number of children classified as obese.

Physical activity behaviours of highly active preschoolers.

BACKGROUND: Understanding the physical activity behaviour of young children who are highly active may provide important guidance for promoting physical activity in preschools. OBJECTIVES: The objective of this study was to describe the movement characteristics of high-active (HA) children during attendance at preschools. METHODS: Children in 20 preschools (n = 231) wore accelerometers and were classified into tertiles of moderate-to-vigorous physical activity. Children's movement characteristics were observed using the Observational System for Recording Physical Activity in Children-Preschool Version. Mixed-model analyses compared movement types between HA children and lower-active (LA) children during the total school day. RESULTS: HA (n = 77) children were observed to be more active than LA children (n = 154) indoors (P < 0.001), but no differences were observed outdoors. HA children were more frequently observed running, crawling, climbing, jumping, skipping, swinging and throwing across the total school day than LA children. Outdoors, HA children participated in more swinging and throwing and less jumping or skipping than LA children. Indoors, HA children spent more time pulling, pushing and running, and less time walking than LA children. CONCLUSIONS: HA children have unique activity patterns. Further interventions to increase physical activity of all preschoolers should increase the time spent outside and include varied activity types throughout the entire school day.

After-school setting, physical activity, and sedentary behavior in 5th grade boys and girls.

After-school hours are considered critical for children's physical activity (PA) and sedentary behaviors (SB); however, whether the after-school setting influences children's activity patterns is unknown. This study examined the influence of after-school setting (i.e., parent report of the child's usual after-school setting) on 5th grade children's PA and SB, and differences by race/ethnicity. Boys whose parents reported they usually attended an after-school program had higher PA than boys who usually went home after school. A significant interaction between race/ethnicity and after-school setting showed that minority girls whose parents reported they usually attended an after-school program had higher PA and engaged in less SB compared with those who usually went home, whereas the activity patterns of white girls did not differ by after-school setting. Children's usual after-school setting affects their activity patterns; after-school programs may potentially increase PA in boys and minority girls.

Assessing sustainability of Lifestyle Education for Activity Program (LEAP).

Sustained intervention effects are needed for positive health impacts in populations; however, few published examples illustrate methods for assessing sustainability in health promotion programs. This paper describes the methods for assessing sustainability of the Lifestyle Education for Activity Program (LEAP). LEAP was a comprehensive school-based intervention that targeted change in instructional practices and the school environment to promote physical activity (PA) in high school girls. Previous reports indicated that significantly more girls in the intervention compared with control schools reported engaging in vigorous PA, and positive long-term effects on vigorous PA also were observed for girls in schools that most fully implemented and maintained the intervention 3 years following the active intervention. In this paper, the seven steps used to assess sustainability in LEAP are presented; these steps provide a model for assessing sustainability in health promotion programs in other settings. Unique features of the LEAP sustainability model include assessing sustainability of changes in instructional practices and the environment, basing assessment on an essential element framework that defined complete and acceptable delivery at the beginning of the project, using multiple data sources to assess sustainability, and assessing implementation longitudinally.

After-school interventions to increase physical activity among youth.

Most children and adolescents do not meet the recommended 60 minutes or more of moderate to vigorous physical activity per day. One attractive approach to increasing physical activity in young people is providing activity through structured after-school programmes. This paper provides a review of the scientific literature on the effects of after-school programmes on physical activity in children and adolescents. After-school physical activity interventions provided mixed results; some increased children's physical activity, others did not. Although after-school programmes have the potential to help children and adolescents engage in regular, enjoyable physical activity, the research on these programmes is limited and, in some cases, methodologically weak. Additional, well-controlled studies are needed to identify the components of after-school programmes that promote physical activity and to determine the level of activity that can be attained when children and adolescents participate in these programmes.