Associations between active commuting, body fat, and body mass index: population based, cross sectional study in the United Kingdom.

OBJECTIVE: To determine if promotion of active modes of travel is an effective strategy for obesity prevention by assessing whether active commuting (walking or cycling for all or part of the journey to work) is independently associated with objectively assessed biological markers of obesity. DESIGN: Cross sectional study of data from the wave 2 Health Assessment subsample of Understanding Society, the UK Household Longitudinal Study (UKHLS). The exposure of interest, commuting mode, was self reported and categorised as three categories: private transport, public transport, and active transport. PARTICIPANTS: The analytic samples (7534 for body mass index (BMI) analysis, 7424 for percentage body fat analysis) were drawn from the representative subsample of wave 2 respondents of UKHLS who provided health assessment data (n = 15,777). MAIN OUTCOME MEASURES: Body mass index (weight (kg)/height (m)(2)); percentage body fat (measured by electrical impedance). RESULTS: Results from multivariate linear regression analyses suggest that, compared with using private transport, commuting by public or active transport modes was significantly and independently predictive of lower BMI for both men and women. In fully adjusted models, men who commuted via public or active modes had BMI scores 1.10 (95% CI 0.53 to 1.67) and 0.97 (0.40 to 1.55) points lower, respectively, than those who used private transport. Women who commuted via public or active modes had BMI scores 0.72 (0.06 to 1.37) and 0.87 (0.36 to 0.87) points lower, respectively, than those using private transport. Results for percentage body fat were similar in terms of magnitude, significance, and direction of effects. CONCLUSIONS: Men and women who commuted to work by active and public modes of transport had significantly lower BMI and percentage body fat than their counterparts who used private transport. These associations were not attenuated by adjustment for a range of hypothesised confounding factors

Change in commute mode and body-mass index: prospective, longitudinal evidence from UK Biobank.

BACKGROUND: Insufficient physical activity is a determinant of obesity and cardiovascular disease. Active travel to work has declined in high-income countries in recent decades. We aimed to determine which socioeconomic and demographic characteristics predicted switching to or from active commuting, whether switching from passive to active commuting (or the reverse) independently predicts change in objectively measured body-mass index (BMI), and to ascertain whether any association is attenuated by socioeconomic, demographic, or behavioural factors. METHODS: This study used longitudinal data from UK Biobank. Baseline data collection occurred at 22 centres between March, 2006, and July, 2010, with a repeat assessment at one centre (Stockport) between August, 2012, and June, 2013, for a subset of these participants. Height and weight were objectively measured at both timepoints. We included individuals present at both timepoints with complete data in the analytic sample. Participants were aged 40-69 years and commuted from home to a workplace on a regular basis at both baseline and follow-up. Two exposures were investigated: transition from car commuting to active or public transport commuting and transition from active or public transport to car commuting. Change in BMI between baseline and repeat assessment was the outcome of interest, assessed with bivariate and multivariate logistic regression models. FINDINGS: 502 656 individuals provided baseline data, with 20 346 participating in the repeat assessment after a median of 4·4 years (IQR 3·7-4·9). 5861 individuals were present at both timepoints and had complete data for all analytic variables. Individuals who transitioned from car commuting at baseline to active or public transportation modes at follow-up had a decrease in BMI of -0·30 kg/m2 (95% CI -0·47 to -0·13; p=0·0005). Conversely, individuals who transitioned from active commuting at baseline to car commuting at follow-up had a BMI increase of 0·32 kg/m2 (0·13 to 0·50; p=0·008). These effects were not attenuated by adjustment for hypothesised confounders. Change in household income emerged as a determinant of commute mode transitions. INTERPRETATION: Incorporation of increased levels of physical activity as part of the commute to work could reduce obesity among middle-aged adults in the UK. FUNDING: UK Medical Research Council

Do perceptions of the neighbourhood food environment predict fruit and vegetable intake in low-income neighbourhoods?

The aim of this study is to investigate the extent to which perceptions of the quality, variety and affordability of local food retail provision predict fruit and vegetable intake. Secondary analysis of baseline data from the Philadelphia Neighbourhood Food Environment Study was undertaken. This study investigating the role of the neighbourhood food environment on diet and obesity comprised a random sample of households from two low-income Philadelphia neighbourhoods, matched on socio-demographic characteristics and food environment. The analytic sample comprised adult men and women aged 18-92 (n=1263). Perception of the food environment was measured using five related dimensions pertaining to quality, choice and expense of local food outlets and locally available fruits and vegetables. The outcome, portions of fruits and vegetables consumed per day, was measured using the Block Food Frequency Questionnaire. Results from multivariate regression analyses suggest that measured dimensions of perceived neighbourhood food environment did not predict fruit and vegetable consumption. Further investigation of what constitutes an individual's 'true' food retail environment is required

A Systematic Review of Food Deserts, 1966-2007

INTRODUCTION: "Food deserts," areas characterized by poor access to healthy and affordable food, may contribute to social and spatial disparities in diet and diet-related health outcomes. However, the extent to which food deserts exist is debated. We review the evidence for the existence of food deserts in socioeconomically disadvantaged areas. METHODS: We conducted a systematic review of primary, quantitative, observational studies, published in English or French, that used geographic or market-basket approaches in high-income countries. The literature search included electronic and hand searches and peer-reviewed and grey literature from 1966 through 2007. We also contacted key researchers to identify other studies. We analyzed the findings and quality of the studies qualitatively. RESULTS: Forty-nine studies in 5 countries met inclusion criteria; the amount and consistency of the evidence varied by country. These studies were a mix of geographic and market-basket approaches, but the methodologic quality of studies and completeness of reported findings were mixed. We found clear evidence for disparities in food access in the United States by income and race. Findings from other high-income countries were sparse and equivocal. CONCLUSION: This review suggests that food deserts exist in the United States, where area-level deprivation compounds individual disadvantage. Evidence for the existence of food deserts in other high-income nations is weak

Lost in translation? Theory, policy and practice in systems-based environmental approaches to obesity prevention in the Healthy Towns programme in England.

This paper explores how system-wide approaches to obesity prevention were 'theorised' and translated into practice in the 'Healthy Towns' programme implemented in nine areas in England. Semi-structured interviews with 20 informants, purposively selected to represent national and local programme development, management and delivery were undertaken. Results suggest that informants articulated a theoretical understanding of a system-wide approach to obesity prevention, but simplifying this complex task in the context of uncertainty over programme aims and objectives, and absence of a clear direction from the central government, resulted in local programmes relying on traditional multi-component approaches to programme delivery. The development of clear, practical guidance on implementation should form a central part of future system-wide approaches to obesity prevention

New neighborhood grocery store increased awareness of food access but did not alter dietary habits or obesity.

National and local policies to improve diet in low-income US populations include increasing physical access to grocery stores and supermarkets in underserved neighborhoods. In a pilot study that evaluated the impacts of opening a new supermarket in a Philadelphia community considered a "food desert"-part of the Pennsylvania Fresh Food Financing Initiative-we found that the intervention moderately improved residents' perceptions of food accessibility. However, it did not lead to changes in reported fruit and vegetable intake or body mass index. The effectiveness of interventions to improve physical access to food and reduce obesity by encouraging supermarkets to locate in underserved areas therefore remains unclear. Nevertheless, the present findings suggest that simply improving a community's retail food infrastructure may not produce desired changes in food purchasing and consumption patterns. Complementary policy changes and interventions may be needed to help consumers bridge the gap between perception and action. The replication of our findings in other settings and research into the factors that influence community residents' receptivity to improved food access are urgently required

Healthy Cities: The Impact of Food Retail-led Regeneration on Food Access, Choice and Retail Structure

The health, social and planning policy agendas which have focused on the issue of food deserts, food access and food choice provide the context for this study of the outcomes of a large scale food retail intervention in Springburn, Glasgow. Through an analysis of changing retail structure and foodscape health impacts on food provision, food choice and physical and economic accessibility. This is set within the regeneration context of the Tesco St Rollox Partnership. Conclusions are reached on the potential for such schemes to deliver a range of diet, health, social, regeneration and planning policy goals

Interrupted time series regression for the evaluation of public health interventions: a tutorial.

Interrupted time series (ITS) analysis is a valuable study design for evaluating the effectiveness of population-level health interventions that have been implemented at a clearly defined point in time. It is increasingly being used to evaluate the effectiveness of interventions ranging from clinical therapy to national public health legislation. Whereas the design shares many properties of regression-based approaches in other epidemiological studies, there are a range of unique features of time series data that require additional methodological considerations. In this tutorial we use a worked example to demonstrate a robust approach to ITS analysis using segmented regression. We begin by describing the design and considering when ITS is an appropriate design choice. We then discuss the essential, yet often omitted, step of proposing the impact model a priori. Subsequently, we demonstrate the approach to statistical analysis including the main segmented regression model. Finally we describe the main methodological issues associated with ITS analysis: over-dispersion of time series data, autocorrelation, adjusting for seasonal trends and controlling for time-varying confounders, and we also outline some of the more complex design adaptations that can be used to strengthen the basic ITS design

Corrigendum to: Interrupted time series regression for the evaluation of public health interventions: a tutorial.

The originally published version of this article contained an algebraic definition of the regression model for interrupted time series (ITS) that could lead to erroneous interpretations of the estimated parameters. This model was presented in the equation at page 351, right column, and the following text. We provide here a more accurate definition