Habitual active transport, TV viewing and weight gain: a four year follow-up study

Sitting Time and Obesity or Abdominal Obesity in Older South Koreans: Korean National Health and Nutrition Examination Survey 2013

We examined relationships between sitting time and obesity or abdominal obesity according to sex and socioeconomic status in elderly people. We analyzed data from the Korean National Health and Nutrition Examination Survey 2013, and 1565 participants were included in the study. Multivariate logistic regression analysis was used to examine relationships between sitting time and obesity or abdominal obesity according to sex and socioeconomic status. Sitting time was positively correlated with body mass index in men and women and waist circumference in men. When considering socioeconomic factors, men who sat for 5 hours or longer and fell within the lowest income were more likely to have obesity and abdominal obesity relative to men who sat for 5 hours or shorter and earned higher incomes (odds ratio [95% confidence interval] = 1.80 [1.14-2.84] and 1.63 [1.02-2.61] respectively), and women who sat for 5 hours or longer and fell within the lowest educational level were more likely to have obesity relative to women who sat for 5 hours or less and were educated to a higher level (1.24 [1.01-1.85]). Strategies to reduce sedentary behavior would help to prevent obesity in older men who earn low incomes and women with lower levels of educational attainment.

Do sedentary behaviors mediate associations between socio-demographic characteristics and BMI in women living in socio-economically disadvantaged neighborhoods?

BACKGROUND

Women living in deprived neighborhoods are a risk group for overweight and obesity, particularly during the childbearing years. Several socio-demographic characteristics may compound this risk, but little is known about why this might be the case. Sedentary behaviors are emerging as a socio-demographically patterned risk factor for obesity. The purpose of the present study was to assess socio-demographic differences in sedentary behaviors, and to examine whether these behaviors could explain the relation between socio-demographic variables and BMI (BMI) in this risk group.

METHODS

Women aged 18-46 years were recruited from 40 urban and 40 rural deprived neighborhoods in Victoria, Australia. In total, 3879 women reported socio-demographic variables (age, educational level, employment status, marital status, number of children, residential location and country of birth), sedentary behaviors (television time, computer time, total screen time and total sedentary time), physical activity, and height and weight, which were used to calculate BMI. For each socio-demographic variable, four single mediation models were conducted using two-level mixed-models regression analyses. Mediating effects were examined using the MacKinnon product-of-coefficients procedure and the Sobel test.

RESULTS

All socio-demographic variables were significantly associated with sedentary behaviors. Single mediation analyses revealed that television time (αβ = 0.017, 95% CI = 0.000, 0.030) and total screen time (αβ = 0.006, 95% CI = 0.000, 0.012) mediated 14.1% and 4.9% of the relationship between educational level and BMI, respectively. Total screen time mediated 45.1% of the relationship between employment status and BMI (αβ = -0.020, 95% CI = -0.033, -0.006), and television time mediated 8.2% of the relationship between country of birth and BMI (αβ = -0.008, 95% CI = -0.016, -0.001).

CONCLUSION

Sedentary behaviors differed depending on socio-demographic characteristics, and partly explained the relationship between socio-demographic factors and BMI in this sample of women. Both television time and total screen time are potential behaviors to target in future programs aimed at reducing socio-demographic disparities in overweight and obesity.

Active commuting and its associations with blood pressure and adiposity markers in children

OBJECTIVE

The positive impacts of active travel on health markers still require further research, especially in youth populations with higher risk of obesity. The present study aimed to analyze the associations between blood pressure and adiposity risk (BPAR) and active travel to school in children.

METHODS

The sample comprised 665 Portuguese children (345 boys) aged 7-9 years. Data on height, weight, and skinfold thickness were collected by a trained fieldworker as well as data on BPAR between March 2009 and January 2010 (data were analyzed in 2012-2013). Information on mode and duration of travel to school (i.e. exposure) was gathered by questionnaire. Outcome variables were statistically normalized and expressed as Z scores. A BPAR score was computed as the mean of the Z scores. Multiple linear regression, with adjustments for confounders, was used.

RESULTS

Active commuting was inversely associated with BPAR after adjustment for several potential confounders. After adjusting for BMI, the strength of the relationship between BPAR and active commuting was significantly improved (p≤0.01).

CONCLUSIONS

Findings showed an independent association between the clustered BPAR and active commuting in children aged 7-9 years.

High sitting time or obesity: Which came first? Bidirectional association in a longitudinal study of 31,787 Australian adults

OBJECTIVE

Evidence on the direction of the association between sitting time and obesity is limited. The prospective associations between baseline total sitting time and subsequent changes in body mass index (BMI), and baseline BMI and subsequent changes in sitting time were examined.

METHODS

BMI, from self-reported height and weight, and a single-item measure of sitting time were ascertained at two time points (3.4 ± 0.96 years apart) in a prospective questionnaire-based cohort of 31,787 Australians aged 45-65 years without severe physical limitations.

RESULTS

In a fully adjusted model, baseline obesity was associated with increased sitting time among all participants (adjusted odds ratio [aOR] = 1.20 [95% CI, 1.11-1.30]; P < 0.001) and in most subgroups. The association was significant among those who were sitting <4 hours/day (aOR = 1.24 [95% CI, 1.07-1.44]; P = 0.004) and 4-8 hours/day at baseline (aOR=1.18 [95% CI, 1.06-1.32]; P = 0.003), but not in the high sitting groups (P = 0.111 and 0.188 for 8-11 and ≥11 sitting hours/day, respectively). Nonsignificant and inconsistent results were observed for the association between baseline sitting time and subsequent change in BMI.

CONCLUSIONS

Our findings support the hypothesis that obesity may lead to a subsequent increase in total sitting time, but the association in the other direction is unclear.

Sedentary behaviours in mid-adulthood and subsequent body mass index

OBJECTIVES

It is unclear whether sedentary behaviour, and the domain in which it occurs, is related to body mass index (BMI) change. We aim to elucidate whether sedentary behaviour is prospectively related to BMI change using markers from three domains (leisure, work and commuting).

METHODS

Among employed 1958 British birth cohort members (n = 6,562), we analysed whether TV-viewing, work sitting (six categories: 0 h/d to >4 h/d) and motorised commuting (at 45 y) were related to BMI (at 45 y and 50 y) and BMI change 45-50 y, after adjusting for lifestyle and socioeconomic factors.

RESULTS

Per category higher TV-viewing, 45 y and 50 y BMI were higher by 0.69 kg/m(2) (95% CI: 0.59,0.80) and 0.75 kg/m(2) (0.64,0.86) respectively. A category higher TV-viewing was associated with 0.11 kg/m(2) (0.06,0.17) increased BMI 45-50 y, attenuating to 0.06 kg/m(2) (0.01,0.12) after adjustment. There was no trend for work sitting with 45 y or 50 y BMI, nor, after adjustment, for BMI change. However, those sitting 2-3 h/d had greater BMI gain by 0.33 kg/m(2) (0.10,0.56) compared to those sitting 0-1 h/d. Associations between TV-viewing and BMI change were independent of work sitting. Motorised commuting was associated with 45 y, but not 50 y BMI or change.

CONCLUSIONS

TV-viewing is associated with BMI gain in mid-adulthood; evidence is weaker for other sedentary behaviours.

Active transport and health outcomes: findings from a population study in Jiangsu, China

To investigate the prevalence of active transport (AT, defined as walking or bicycling for transport) and to explore the association between AT and health outcomes, we conducted a population-based cross-sectional study in Jiangsu, China, where walking and bicycling are still the main modes of transport. In this study, 8400 community residents aged 18 or above were interviewed following a multistage random sampling method (100% response rate). Face-to-face questionnaire survey data, anthropometric measurements, and biochemical data from blood tests were collected. Results show that 49.6% of the subjects, as part of daily transport, actively traveled on average 5.3 days per week, 53.5 minutes per day, and 300.3 minutes per week. There was an inverse correlation between AT and some health outcomes: AT respondents had a higher prevalence of cholesterol disorder; AT respondents who actively travelled every day had a higher risk of diabetes, whilst AT respondents with shorter daily or weekly duration had a lower risk of obesity, central obesity, and cholesterol disorder. Moreover, AT influences more health aspects among urban residents than among rural residents. Findings of this study do not support the notion that AT is beneficial to population health. Further research is needed in determining the negative side effects of AT.

Sitting behavior and obesity: evidence from the Whitehall II study

BACKGROUND

Prospective studies report associations between indicators of time spent sitting and obesity risk. Most studies use a single indicator of sedentary behavior and are unable to clearly identify whether sedentary behavior is a cause or a consequence of obesity.

PURPOSE

To investigate cross-sectional and prospective associations between multiple sitting time indicators and obesity and examine the possibility of reverse causality.

METHODS

Using data from the Whitehall II cohort, multiple logistic models were fitted to examine associations between prevalent obesity (BMI ≥30) at Phase 5 (1997-1999), and incident obesity between Phases 5 and 7 (2003-2004) across four levels of five sitting exposures (work sitting, TV viewing, non-TV leisure-time sitting, leisure-time sitting, and total sitting). Using obesity data from three prior phases (1985-1988, 1991-1993; and recalled weight at age 25 years), linear regression models were fitted to examine the association between prior obesity and sitting time at Phase 5. Analyses were conducted in 2012.

RESULTS

None of the sitting exposures were associated with obesity either cross-sectionally or prospectively. Obesity at one previous measurement phase was associated with a 2.43-hour/week (95% CI=0.07, 4.78) increase in TV viewing; obesity at three previous phases was associated with a 7.42-hour/week (95% CI=2.7, 12.46) increase in TV-viewing hours/week at Phase 5.

CONCLUSIONS

Sitting time was not associated with obesity cross-sectionally or prospectively. Prior obesity was prospectively associated with time spent watching TV per week but not other types of sitting.

Commuting by car: weight gain among physically active adults

BACKGROUND

Prolonged sitting, including time spent sitting in cars, is detrimentally associated with health outcomes.

PURPOSE

This study examined whether commuting by car was associated with adults' weight gain over 4 years.

METHODS

Among 822 adult residents of Adelaide, Australia, weight change was ascertained from self-reported weight at baseline (2003-2004) and at follow-up (2007-2008). Using time spent for car commuting and work status at baseline, participants were categorized as non-car commuters, occasional car commuters, and daily car commuters. Multilevel linear regression (conducted in 2012) examined associations of weight change with car-commuting category, adjusting for potential confounding variables, for the whole sample, and among those who were physically inactive or active (≥150 minutes/week) in their leisure time.

RESULTS

For the overall sample, adjusted mean weight gain (95% CI) over 4 years was 1.26 (0.64, 1.89) kg for non-car commuters; 1.53 (0.69, 2.37) kg for occasional car commuters; and 2.18 (1.44, 2.92) kg for daily car commuters (p for trend=0.090). Stratified analyses found a stronger association for those with sufficient leisure-time physical activity. For non-car commuters with sufficient leisure-time physical activity, the adjusted mean weight gain was 0.46 (-0.43, 1.35) kg, which was not significantly greater than 0.

CONCLUSIONS

Over 4 years, those who used cars daily for commuting tended to gain more weight than those who did not commute by car. This relationship was pronounced among those who were physically active during leisure time. Reducing sedentary time may prevent weight gain among physically active adults.

Sedentary behavior: understanding and influencing adults' prolonged sitting time

Too much sitting is now understood to be a health risk that is additional to, and distinct from, too little exercise. There is a rapidly-accumulating evidence on relationships of prolonged sedentary time and patterns of sedentary time with cardio-metabolic risk biomarkers and health outcomes. There is, however, the need to gather dose-response evidence and develop a broader understanding of the set of mechanisms linking sedentary behavior to health outcomes. In addition to the further understanding of the associated health risks, there is a new health-behavior, and epidemiological and experimental research agenda to be pursued, which include measurement studies; understanding the relevant determinants-particularly environmental determinants of sedentary behavior; and, developing effective interventions. A broad-based body of evidence is needed to inform the research-translation agenda-identifying and developing the future public health initiatives, environmental and policy changes and clinical guidelines that may be required.