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      International Study of Objectively-measured Physical Activity and Sedentary Time with Body Mass Index and Obesity: IPEN Adult Study


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          Physical activity (PA) has been consistently implicated in the etiology of obesity, while recent evidence on the importance of sedentary time remains inconsistent. Understanding of dose-response associations of PA and sedentary time with overweight and obesity in adults can be improved with large-scale studies using objective measures of PA and sedentary time. The purpose of this study was to examine the strength, direction and shape of dose-response associations of accelerometer-based PA and sedentary time with BMI and weight status in 10 countries, and the moderating effects of study site and gender.


          Data from the International Physical activity and the Environment Network (IPEN) Adult study were used. IPEN Adult is an observational multi-country cross-sectional study, and 12 sites in 10 countries are included. Participants wore an accelerometer for seven consecutive days, completed a socio-demographic questionnaire and reported height and weight. In total, 5712 adults (18–65 years) were included in the analyses. Generalized additive mixed models, conducted in R, were used to estimate the strength and shape of the associations.


          A curvilinear relationship of accelerometer-based moderate-to-vigorous PA and total counts/minute with BMI and the probability of being overweight/obese was identified. The associations were negative, but weakened at higher levels of moderate-to-vigorous PA (>50 min/day) and higher counts/minute. No associations between sedentary time and weight outcomes were found. Complex site- and gender-specific findings were revealed for BMI, but not for weight status.


          Based on these results, the current Institute of Medicine recommendation of 60 minutes/day of moderate-to-vigorous PA to prevent weight gain in normal-weight adults was supported. No relationship between sedentary time and the weight outcomes was present, calling for further examination. If moderator findings are confirmed, the relationship between PA and BMI may be country- and gender-dependent, which could have important implications for country-specific health guidelines.

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          Most cited references 40

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          Calibration of the Computer Science and Applications, Inc. accelerometer.

          We established accelerometer count ranges for the Computer Science and Applications, Inc. (CSA) activity monitor corresponding to commonly employed MET categories. Data were obtained from 50 adults (25 males, 25 females) during treadmill exercise at three different speeds (4.8, 6.4, and 9.7 km x h(-1)). Activity counts and steady-state oxygen consumption were highly correlated (r = 0.88), and count ranges corresponding to light, moderate, hard, and very hard intensity levels were or = 9499 cnts x min(-1), respectively. A model to predict energy expenditure from activity counts and body mass was developed using data from a random sample of 35 subjects (r2 = 0.82, SEE = 1.40 kcal x min(-1)). Cross validation with data from the remaining 15 subjects revealed no significant differences between actual and predicted energy expenditure at any treadmill speed (SEE = 0.50-1.40 kcal x min(-1)). These data provide a template on which patterns of activity can be classified into intensity levels using the CSA accelerometer.
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            Sedentary behaviors and subsequent health outcomes in adults a systematic review of longitudinal studies, 1996-2011.

            To systematically review and provide an informative synthesis of findings from longitudinal studies published since 1996 reporting on relationships between self-reported sedentary behavior and device-based measures of sedentary time with health-related outcomes in adults. Studies published between 1996 and January 2011 were identified by examining existing literature reviews and by systematic searches in Web of Science, MEDLINE, PubMed, and PsycINFO. English-written articles were selected according to study design, targeted behavior, and health outcome. Forty-eight articles met the inclusion criteria; of these, 46 incorporated self-reported measures including total sitting time; TV viewing time only; TV viewing time and other screen-time behaviors; and TV viewing time plus other sedentary behaviors. Findings indicate a consistent relationship of self-reported sedentary behavior with mortality and with weight gain from childhood to the adult years. However, findings were mixed for associations with disease incidence, weight gain during adulthood, and cardiometabolic risk. Of the three studies that used device-based measures of sedentary time, one showed that markers of obesity predicted sedentary time, whereas inconclusive findings have been observed for markers of insulin resistance. There is a growing body of evidence that sedentary behavior may be a distinct risk factor, independent of physical activity, for multiple adverse health outcomes in adults. Prospective studies using device-based measures are required to provide a clearer understanding of the impact of sedentary time on health outcomes. Copyright © 2011 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.
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              Breaks in sedentary time: beneficial associations with metabolic risk.

              Total sedentary (absence of whole-body movement) time is associated with obesity, abnormal glucose metabolism, and the metabolic syndrome. In addition to the effects of total sedentary time, the manner in which it is accumulated may also be important. We examined the association of breaks in objectively measured sedentary time with biological markers of metabolic risk. Participants (n = 168, mean age 53.4 years) for this cross-sectional study were recruited from the 2004-2005 Australian Diabetes, Obesity and Lifestyle study. Sedentary time was measured by an accelerometer (counts/minute(-1) or = 100) was considered a break. Fasting plasma glucose, 2-h plasma glucose, serum triglycerides, HDL cholesterol, weight, height, waist circumference, and resting blood pressure were measured. MatLab was used to derive the breaks variable; SPSS was used for the statistical analysis. Independent of total sedentary time and moderate-to-vigorous intensity activity time, increased breaks in sedentary time were beneficially associated with waist circumference (standardized beta = -0.16, 95% CI -0.31 to -0.02, P = 0.026), BMI (beta = -0.19, -0.35 to -0.02, P = 0.026), triglycerides (beta = -0.18, -0.34 to -0.02, P = 0.029), and 2-h plasma glucose (beta = -0.18, -0.34 to -0.02, P = 0.025). This study provides evidence of the importance of avoiding prolonged uninterrupted periods of sedentary (primarily sitting) time. These findings suggest new public health recommendations regarding breaking up sedentary time that are complementary to those for physical activity.

                Author and article information

                Int J Obes (Lond)
                Int J Obes (Lond)
                International journal of obesity (2005)
                20 June 2014
                02 July 2014
                February 2015
                01 August 2015
                : 39
                : 2
                : 199-207
                [1 ]Research Foundation Flanders, Brussels, Belgium
                [2 ]Department of Movement and Sport Sciences, Faculty of Medicine and Health Sciences, Ghent University, Belgium
                [3 ]Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University, Burwood Victoria, Australia
                [4 ]Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland, New Zealand
                [5 ]Research Group of Physical Activity and Quality of Life, School of Health and Biosciences, Pontificia Universidade Catolica do Parana, Curitiba, Brazil
                [6 ]Department of Physical Education, Universidade Federal do Parana, Curitiba, Brazil
                [7 ]Centre for Research and Action in Public Health, University of Canberra, ACT, Australia
                [8 ]Department of Public Health, School of Medicine, Universidad de los Andes Carrera, Bogotá, Colombia
                [9 ]Institute of Active Lifestyle, Faculty of Physical Culture, Palacký Universitsy, Tř. Míru 115, 771 11, Olomouc. Czech Republic
                [10 ]Research Unit for Active Living, Department of Sport Sciences and Clinical Biomechanics, University of Southern Denmark
                [11 ]Institute of Human Performance, Hong Kong University, Hong Kong
                [12 ]Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, Georgia, USA
                [13 ]Department of Health Sciences, Public University of Navarra, Pamplona, Spain
                [14 ]Baker IDI Heart and Diabetes Institute, Melbourne, Australia; School of Population Health, the University of Queensland; School of Population and Global Health, Melbourne University; Department of Medicine, Monash University
                [15 ]Department of Family and Preventive Medicine, University of California, San Diego
                Author notes
                Corresponding author details Dr. Delfien Van Dyck, Department of Movement and Sport Sciences, Watersportlaan 2, B-9000 Gent, Belgium, Tel: + 32 9 264 63 23 - Fax: + 32 9 264 64 84, Delfien.VanDyck@ 123456UGent.be

                Nutrition & Dietetics

                obesity, accelerometers, exercise, sitting


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