Background. Increasing evidence suggests that vigorous physical activity (VPA) in youth may yield greater health benefits than moderate (MPA) or moderate-tovigorous physical activity (MVPA). The purpose of this review was to assess the relationship between PA intensity and body composition, cardiorespiratory fitness (CRF), and cardiometabolic (CM) biomarkers in youth. Methods. We conducted a systematic review of observational studies examining PA intensity and selected health outcomes in youth aged 6 to 18 years. Fortyfive articles were selected for final review. Results. VPA was more strongly associated with reduced body fat and central adiposity compared with MPA and/or MVPA. Additionally, VPA was more strongly associated with increased CRF when compared with lower intensities. Findings were inconclusive between all PA intensity levels and CM biomarkers, and several significant relationships observed for VPA were attenuated when controlling for CRF. Conclusions. A potential VPA dose is identified as yielding favorable health benefits in adiposity and fitness. While CM biomarkers were not consistently associated with PA intensity level, the literature suggests VPA may yield health benefits above those received from MPA for reduced adiposity and improved CRF. This review highlights the need for longitudinal observational and experimental studies to determine optimal VPA dose for CM health in youth.

Background: Diverse environmental factors are associated with physical activity (PA) and healthy eating (HE) among youth. However, no study has created a comprehensive obesogenic environment index for children that can be applied at a large geographic scale. The purpose of this study was to describe the development of a childhood obesogenic environment index (COEI) at the county level across the United States. Methods: A comprehensive search of review articles (n = 20) and input from experts (n = 12) were used to identify community-level variables associated with youth PA, HE, or overweight/obesity for potential inclusion in the index. Based on strength of associations in the literature, expert ratings, expertise of team members, and data source availability, 10 key variables were identifiedsix related to HE (# per 1000 residents for grocery/superstores, farmers markets, fast food restaurants, full-service restaurants, and convenience stores; as well as percentage of births at baby (breastfeeding)-friendly facilities) and four related to PA (percentage of population living close to exercise opportunities, percentage of population < 1 mile from a school, a composite walkability index, and number of violent crimes per 1000 residents). Data for each variable for all counties in the U.S. (n = 3142) were collected from publicly available sources. For each variable, all counties were ranked and assigned percentiles ranging from 0 to 100. Positive environmental variables (e.g., grocery stores, exercise opportunities) were reverse scored such that higher values for all variables indicated a more obesogenic environment. Finally, for each county, a total obesogenic environment index score was generated by calculating the average percentile for all 10 variables.

The present study was conducted to determine the association between fibre intake and insulin resistance in 264 women using a crosssectional design. Insulin resistance was indexed using homeostasis model assessment of insulin resistance (HOMA-IR) (US formula: fasting insulin (mU/ml) £ fasting glucose (mg/dl)/405 international formula: fasting glucose (mmol/l) £ fasting insulin (mU/l)/22.5). Fibre and energy consumption were assessed using 7 d weighed food records. Fibre was expressed as g/4184 kJ (1000 kcal). Body fat percentage (BF%) was measured using the BOD POD, and physical activity (PA) was ascertained using Actigraph accelerometers (Health One Technology) worn for seven consecutive days. Women with high total fibre intakes (F ¼ 4·58, P¼ 0·0332) or high soluble fibre intakes (F ¼ 7·97, P¼ 0·0051) had significantly less insulin resistance than their counterparts. Participants with high insoluble fibre intakes did not differ from their counterparts (F ¼ 0·7, P¼ 0·6875). Adjusting for either PA or BF% weakened the relationships significantly. Controlling for BF% nullified the total fibre -HOMA-IR link (F ¼ 1·96, P¼0·1631) and attenuated the association between soluble fibre and HOMA-IR by 32 % (F ¼ 6·86, P¼0·0094). To create dichotomous variables, fibre intake and HOMA-IR were each divided into two categories using the median (low and high). In women who had high soluble fibre intake (upper 50 %), the OR of having an elevated HOMA-IR level was 0·58 (95 % CI 0·36, 0·94) times that of women with low soluble fibre intake (lower 50 %). After controlling for all of the potential confounding factors simultaneously, the OR was 0·52 (95 % CI 0·29, 0·93). High fibre intake, particularly soluble fibre, is significantly related to lower levels of insulin resistance in women. Part of this association is a function of differences in PA and BF%.

No abstract