Insulin resistance, C-reactive protein, diastolic to systolic blood pressure ratio and epicardial fat are related to sedentary time, and inversely related to physical activity in school-aged children

Background The prominence of sedentary behavior research in health science has grown rapidly. With this growth there is increasing urgency for clear, common and accepted terminology and definitions. Such standardization is difficult to achieve, especially across multi-disciplinary researchers, practitioners, and industries. The Sedentary Behavior Research Network (SBRN) undertook a Terminology Consensus Project to address this need. Method First, a literature review was completed to identify key terms in sedentary behavior research. These key terms were then reviewed and modified by a Steering Committee formed by SBRN. Next, SBRN members were invited to contribute to this project and interested participants reviewed and provided feedback on the proposed list of terms and draft definitions through an online survey. Finally, a conceptual model and consensus definitions (including caveats and examples for all age groups and functional abilities) were finalized based on the feedback received from the 87 SBRN member participants who responded to the original invitation and survey. Results Consensus definitions for the terms physical inactivity, stationary behavior, sedentary behavior, standing, screen time, non-screen-based sedentary time, sitting, reclining, lying, sedentary behavior pattern, as well as how the terms bouts, breaks, and interruptions should be used in this context are provided. Conclusion It is hoped that the definitions resulting from this comprehensive, transparent, and broad-based participatory process will result in standardized terminology that is widely supported and adopted, thereby advancing future research, interventions, policies, and practices related to sedentary behaviors. Electronic supplementary material The online version of this article (doi:10.1186/s12966-017-0525-8) contains supplementary material, which is available to authorized users.

Physical activity (PA) is a behavior that involves bodily movements resulting in energy expenditure. When assessing PA, the goal is to identify the frequency, duration, intensity, and types of behaviors performed during a period of time. Self-report measures of PA include administration of questionnaires and completion of detailed diaries and/or brief logs. Direct measures include motion sensors such as accelerometers, pedometers, heart-rate monitors, and multiple-sensor devices. The PA assessment period can range from a few hours to a lifetime depending on the tools used. Considerations when selecting a PA tool should include the literacy requirements of a tool, the purpose for assessing PA, the recall or time period to measure, the validity evidence of an assessment tool for the populations measured, and the generalizability of the results to diverse populations.

The association between obesity and insulin resistance is an area of much interest and enormous public health impact, with hundreds of articles being published in the last year focused on the possible mechanisms that underlie this association. The purpose to this review is to highlight some of the key recent literature with emphasis on emerging concepts. The specific link between visceral adipose tissue accumulation and insulin resistance continues to be discerned. Visceral adiposity is correlated with accumulation of excess lipid in liver, and results in cell autonomous impairment in insulin signaling. Visceral adipose tissue is also prone to inflammation and inflammatory cytokine production, which also contribute to impairment in insulin signaling. The expansion of visceral adipose tissue and excess lipid accumulation in liver and muscle may result from limited expandability of subcutaneous adipose tissue, due to the properties of its extracellular matrix and capacity for capillary growth. Recent studies underscore the need to better understand the mechanisms linking visceral adiposity with liver fat accumulation, the mechanisms by which ectopic fat accumulation cause insulin resistance, and the mechanisms by which the size of adipose tissue depots is determined.