Transferability of the NHS low-calorie diet programme: A qualitative exploration of factors influencing the programme's transfer ahead of wide-scale adoption.

INTRODUCTION: Although behavioural interventions have been found to help control type 2 diabetes (T2D), it is important to understand how the delivery context can influence implementation and outcomes. The NHS committed to testing a low-calorie diet (LCD) programme designed to support people living with excess weight and T2D to lose weight and improve diabetes outcomes. Understanding what influenced implementation during the programme pilot is important in optimising rollout. This study explored the transferability of the NHS LCD Programme prior to wider adoption. METHODS: Twenty-five interviews were undertaken with stakeholders involved in implementing the LCD programme in pilot sites (health service leads, referring health professionals and programme deliverers). Interviews with programme participants (people living with T2D) were undertaken within a larger programme of work, exploring what worked, for whom and why, which is reported separately. The conceptual Population-Intervention-Environment-Transfer Model of Transferability (PIET-T) guided study design and data collection. Constructs of the model were also used as a deductive coding frame during data analysis. Key themes were identified which informed recommendations to optimise programme transfer. RESULTS: Population: Referral strategies in some areas lacked consideration of population characteristics. Many believed that offering a choice of delivery model would promote acceptability and accessibility of the eligible population. INTERVENTION: Overall, stakeholders had confidence in the LCD programme due to the robust evidence base along with anecdotal evidence, but some felt the complex referral process hindered engagement from GP practices. ENVIRONMENT: Stakeholders described barriers to accessing the programme, including language and learning difficulties. Transferability: Multidisciplinary working and effective communication supported successful implementation. CONCLUSION: Referral strategies to reach underrepresented groups should be considered during programme transfer, along with timely data from service providers on access and programme benefits. A choice of delivery models may optimise uptake. Knowledge sharing between sites on good working practices is encouraged, including increasing engagement with key stakeholders.

The NHS Low-Calorie Diet Digital Programme: Fidelity of behaviour change technique delivery.

AIMS: NHS England commissioned independent service providers to deliver the NHS Low-Calorie Diet Programme pilot. Previous research has illustrated a drift in the fidelity of behaviour change techniques (BCTs) during the delivery of the programme provided through face-to-face group or one-to-one behavioural support. The aim of this study was to assess the delivery fidelity of the BCT content in the digital delivery of the programme. METHODS: Online, app chat and phone call support content was coded using The Behaviour Change Technique Taxonomy. BCTs delivered by each service provider (N = 2) were calculated and compared to the BCTs specified in the NHS service specification and those specified in the providers' programme plans. RESULTS: Between 78% and 83% of the BCTs identified in the NHS service specification were delivered by the service providers. The fidelity of BCT delivery to those specified in providers' programme plans was 60%-65% for provider A, and 82% for provider B. CONCLUSIONS: The BCT content of the digital model used in the NHS-LCD programme adhered well to the NHS service specification and providers' plans. It surpassed what has been previously observed in face-to-face services provided through group or one-on-one behavioural support models.

Process evaluation of implementation of the early stages of a whole systems approach to obesity in a small Island.

BACKGROUND: The small Atlantic island of St Helena is a United Kingdom Overseas Territory (UKOT) with a high prevalence of childhood obesity (over a quarter of 4-5 and 10-11 year olds) and, anecdotally, adulthood obesity and its associated health detriments. St Helena have taken a whole systems approach to obesity (WSAO) to address the issue. A WSAO recognises the factors that impact obesity as a complex system and requires a 'health in all policies' approach. UK academic and public health technical support was provided to the local St Helena delivery team. This process evaluation sought to explore the early stages of the WSAO implementation and implications for the transferability of the approach to other small island developing states and UKOT. METHODS: Data was collected via eight semi-structured interviews, paper based and online surveys, and document analysis. Thematic analysis was used to analyse the data. RESULTS: The analysis identified three factors which aided the first phase of WSAO implementation: (1) senior leaders support for the approach; (2) the academic support provided to establish and develop the approach; and (3) effective adaptation of UK Government resources to suit the local context. Key challenges of early implementation included: maintaining and broadening stakeholder engagement; limited local workforce capacity and baseline knowledge related to obesity and systems thinking; and limited capacity for support from the UK-based academic team due to contract terms and COVID-19 restrictions. CONCLUSIONS: Early stages of implementation of a WSAO in a UKOT can be successful when using UK's resources as a guide and adapting them to a small island context. All participants recommended other small islands adopt this approach. Continued senior support, dedicated leadership, and comprehensive community engagement is needed to progress implementation and provide the foundation for long-term impact. Small island developing states considering adopting a WSAO should consider political will, senior level buy-in and support, funding, and local workforce knowledge and capacity to enable the best chances of successful and sustainable implementation.

Normalisation and equity of referral to the NHS Low Calorie Diet programme pilot; a qualitative evaluation of the experiences of health care staff.

BACKGROUND: Health and wellbeing can be profoundly impacted by both obesity and type 2 diabetes, while the normalisation and equity of care for people living with these non-communicable diseases remain as challenges for local health systems. The National Health Service Low Calorie Diet programme in England, aims to support people to achieve type 2 diabetes remission, while also reducing health inequalities. We have explored the experiences of health care staff who have made a referral to the LCD programme, while identifying effective and equitable delivery of programme referrals, and their normalisation into routine care. METHODS: Nineteen individual semi-structured interviews were completed health care staff in the first year of the Low Calorie Diet programme. Interviewees were purposively sampled from the ten localities who undertook the Low Calorie Diet programme pilot. Each interview explored a number of topics of interest including communication and training, referrals, equity, and demands on primary care, before being subjected to a thematic analysis. RESULTS: From the data, five core themes were identified: Covid-19 and the demands on primary care, the expertise and knowledge of referrers, patient identification and the referral process, barriers to referrals and who gets referred to the NHS LCD programme. Our findings demonstrate the variation in the real world settings of a national diabetes programme. It highlights the challenge of COVID-19 for health care staff, whereby the increased workload of referrals occurred at a time when capacity was curtailed. We have also identified several barriers to referral and have shown that referrals had not yet been normalised into routine care at the point of data collection. We also raise issues of equity in the referral process, as not all eligible people are informed about the programme. CONCLUSIONS: Referral generation had not yet been consistently normalised into routine care, yet our findings suggest that the LCD programme runs the risk of normalising an inequitable referral process. Inequalities remain a significant challenge, and the adoption of an equitable referral process, normalised at a service delivery level, has the capacity to contribute to the improvement of health inequalities.

Can the delivery of behavioural support be improved in the NHS England Low-Calorie Diet Programme? An observational study of behaviour change techniques.

BACKGROUND: Previous research has illustrated a drift in the fidelity of behaviour change techniques (BCTs) during the design of the pilot NHS England Low-Calorie Diet (NHS-LCD) Programme. This study evaluated a subsequent domain of fidelity, intervention delivery. Two research questions were addressed: (1) To what extent were BCTs delivered with fidelity to providers programme plans? (2) What were the observed barriers and facilitators to delivery? METHODS: A mixed-methods sequential explanatory design was employed. Remote delivery of one-to-one and group-based programmes were observed. A BCT checklist was developed using the BCT Taxonomy v1; BCTs were coded as present, partially delivered, or absent during live sessions. Relational content analysis of field notes identified observed barriers and facilitators to fidelity. RESULTS: Observations of 122 sessions across eight samples and two service providers were completed. Delivery of the complete NHS-LCD was observed for five samples. Fidelity ranged from 33% to 70% across samples and was higher for group-based delivery models (64%) compared with one-to-one models (46%). Barriers and facilitators included alignment with the programme's target behaviours and outcomes, session content, time availability and management, group-based remote delivery, and deviation from the session plan. CONCLUSIONS: Overall, BCTs were delivered with low-to-moderate fidelity. Findings indicate a dilution in fidelity during the delivery of the NHS-LCD and variation in the fidelity of programmes delivered across England. Staff training could provide opportunities to practice the delivery of BCTs. Programme-level changes such as structured activities supported by participant materials and with sufficient allocated time, might improve the delivery of BCTs targeting self-regulation.

Does the design of the NHS Low-Calorie Diet Programme have fidelity to the programme specification? A documentary review of service parameters and behaviour change content in a type 2 diabetes intervention.

BACKGROUND: NHS England commissioned four independent service providers to pilot low-calorie diet programmes to drive weight loss, improve glycaemia and potentially achieve remission of Type 2 Diabetes across 10 localities. Intervention fidelity might contribute to programme success. Previous research has illustrated a drift in fidelity in the design and delivery of other national diabetes programmes. AIMS: (1) To describe and compare the programme designs across the four service providers; (2) To assess the fidelity of programme designs to the NHS England service specification. METHODS: The NHS England service specification documents and each provider's programme design documents were double-coded for key intervention content using the Template for Intervention Description and Replication Framework and the Behaviour Change Technique (BCT) Taxonomy. RESULTS: The four providers demonstrated fidelity to most but not all of the service parameters stipulated in the NHS England service specification. Providers included between 74% and 87% of the 23 BCTs identified in the NHS specification. Twelve of these BCTs were included by all four providers; two BCTs were consistently absent. An additional seven to 24 BCTs were included across providers. CONCLUSIONS: A loss of fidelity for some service parameters and BCTs was identified across the provider's designs; this may have important consequences for programme delivery and thus programme outcomes. Furthermore, there was a large degree of variation between providers in the presence and dosage of additional BCTs. How these findings relate to the fidelity of programme delivery and variation in programme outcomes and experiences across providers will be examined.

Investigating where adolescents engage in moderate to vigorous physical activity and sedentary behaviour: An exploratory study.

BACKGROUND: There is a persistent lack of understanding on the influence of the environment on behaviour and health. While the environment is considered an important modifiable determinant of health behaviour, past research assessing environments often relies on static, researcher-defined buffers of arbitrary distance. This likely leads to misrepresentation of true environmental exposures. This exploratory study aims to compare researcher-defined and self-drawn buffers in reflecting the spaces and time adolescents engage in physical activity (PA) and sedentary behaviour. It also investigates if adolescent's access the PA facility and greenspace nearest their home or school for PA, as well as examine how much time adolescents spent in PA at any PA facilities and greenspaces. METHODS: Adolescents (aged 14-18 years; n = 34) were recruited from schools in West Yorkshire, England. Seven consecutive days of global positioning system (GPS) and accelerometer data were collected at 15 second intervals. Using ArcGIS, we compared 30 different researcher-defined buffers including: radial, network and ellipse buffers at 400m, 800m, 1000m, 1600m and 3000m and participant-defined self-drawn neighbourhoods to objectively measured PA and sedentary space and PA time. Location of PA was also compared to Points of Interest data to determine if adolescents use the nearest PA facility or greenspace to their home or school and to examine how much PA was undertaken within these locations. RESULTS: Our exploratory findings show the inadequacy of researcher-defined buffer size in assessing MVPA space or sedentary space. Furthermore, less than 35% of adolescents used the greenspaces or PA facilities nearest to their home or school. Approximately 50% of time spent in PA did not occur within the home, school, PA facility, or greenspace environments. CONCLUSION: Our exploratory findings help to begin to quantify the inadequacy of researcher-defined, and self-drawn buffers in capturing adolescent MVPA and sedentary space, as well as time spent in PA. Adolescents often do not use PA facilities and greenspaces nearest their home and school and a large proportion of PA is achieved outside PA facilities and greenspaces. Further research with larger samples are needed to confirm the findings of this exploratory study.

How is the NHS Low-Calorie Diet Programme expected to produce behavioural change to support diabetes remission: An examination of underpinning theory.

Background: In 2020, the National Health Service Low-Calorie Diet Programme (NHS-LCD) was launched, piloting a total diet (TDR) replacement intervention with behaviour change support for people living with Type 2 Diabetes (T2D) and excess weight. Four independent service providers were commissioned to design and deliver theoretically grounded programmes in localities across England. Aims: 1) to develop a logic model detailing how the NHS-LCD programme is expected to produce changes in health behaviour, and (2) to analyse and evaluate the use of behaviour change theory in providers' NHS-LCD Programme designs. Methods: A documentary review was conducted. Information was extracted from the NHS-LCD service specification documents on how the programme expected to produce outcomes. The Theory Coding Scheme (TCS) was used to analyse theory use in providers' programme design documents. Results: The NHS-LCD logic model included techniques aimed at enhancing positive outcome expectations of programme participation and beliefs about social approval of behaviour change, to facilitate programme uptake and behaviour change intentions. This was followed by techniques aimed at shaping knowledge and enhancing the ability of participants to self-regulate their health behaviours, alongside a supportive social environment and person-centred approach.Application and type of behaviour change theory within service providers' programme designs varied. One provider explicitly linked theory to programme content; two providers linked 63% and 70% of intervention techniques to theory; and there was limited underpinning theory identified in the programme design documents for one of the providers. Conclusion: The nature and extent of theory use underpinning the NHS-LCD varied greatly amongst service providers, with some but not all intervention techniques explicitly linked to theory. How this relates to outcomes across providers should be evaluated. It is recommended that explicit theory use in programme design and evidence of its implementation becomes a requirement of future NHS commissioning processes.

The Action Scales Model: A conceptual tool to identify key points for action within complex adaptive systems.

BACKGROUND: Systems thinking is integral to working effectively within complex systems, such as those which drive the current population levels of overweight and obesity. It is increasingly recognised that a systems approach - which corrals public, private, voluntary and community sector organisations to make their actions and efforts coherent - is necessary to address the complex drivers of obesity. Identifying, implementing and evaluating actions within complex adaptive systems is challenging, and may differ from previous approaches used in public health. METHODS: Within this conceptual article, we present the Action Scales Model (ASM). The ASM is a simple tool to help policymakers, practitioners and evaluators to conceptualise, identify and appraise actions within complex adaptive systems. We developed this model using our collective expertise and experience in working with local government authority stakeholders on the Public Health England Whole Systems Obesity programme. It aligns with, and expands upon, previous models such as the Intervention Level Framework, the Iceberg Model and Donella Meadows' 12 places to intervene within a system. RESULTS: The ASM describes four levels (synonymous with leverage points) to intervene within a system, with deeper levels providing greater potential for changing how the system functions. Levels include events, structures, goals and beliefs. We also present how the ASM can be used to support practice and policy, and finish by highlighting its utility as an evaluative aid. DISCUSSION: This practical tool was designed to support those working at the front line of systems change efforts, and while we use the population prevalence of obesity as an outcome of a complex adaptive system, the ASM and the associated principles can be applied to other issues. We hope that the ASM encourages people to think differently about the systems that they work within and to identify new and potentially more impactful opportunities to leverage change.

Exploring factors affecting individual GPS-based activity space and how researcher-defined food environments represent activity space, exposure and use of food outlets.

BACKGROUND: Obesity remains one of the most challenging public health issues of our modern time. Despite the face validity of claims for influence, studies on the causes of obesity have reported the influence of the food environment to be inconsistent. This inconsistency has been attributed to the variability of measures used by researchers to represent the food environments-Researcher-Defined Food Environments (RDFE) like circular, street-network buffers, and others. This study (i.) determined an individual's Activity Space (AS) (ii.) explored the accuracy of the RDFE in representing the AS, (iii.) investigated the accuracy of the RDFE in representing actual exposure, and (iv.) explored whether exposure to food outlet reflects the use of food outlets. METHODS: Data were collected between June and December 2018. A total of 65 participants collected Global Positioning System (GPS) data, kept receipt of all their food purchases, completed a questionnaire about their personal information and had their weight and height measured. A buffer was created around the GPS points and merged to form an AS (GPS-based AS). RESULTS: Statistical and geospatial analyses found that the AS size of participants working away from home was positively related to the Euclidean distance from home to workplace; the orientation (shape) of AS was also influenced by the direction of workplace from home and individual characteristics were not predictive of the size of AS. Consistent with some previous studies, all types and sizes of RDFE variably misrepresented individual exposure in the food environments. Importantly, the accuracy of the RDFE was significantly improved by including both the home and workplace domains. The study also found no correlation between exposure and use of food outlets. CONCLUSIONS: Home and workplace are key activity nodes in modelling AS or food environments and the relationship between exposure and use is more complex than is currently suggested in both empirical and policy literature.

Understanding how local authorities in England address obesity: A wider determinants of health perspective.

Local government organisations (LAs) have a major role in the prevention and treatment of obesity in England. This study aims to 1) understand what actions are being taken by LAs to address obesity, and 2) determine how actions counter the perceived causes of obesity when mapped against the Wider Determinants of Health (WDoH) model. Thirty-two LAs were invited to complete an Action Mapping Tool, 10 participated. The tool requires LAs to document actions being implemented locally to address obesity. This then enables LAs to map their actions against the perceived causes of obesity, using the WDoH model as an analytical lens. We collated data from the 10 LAs and used an adapted framework synthesis method for analysis. 280 actions were documented across the 10 LAs; almost 60% (n = 166) targeted Individual Lifestyle Factors (ILF), with 7.1% (n = 20), 16.8% (n = 47) and 16.4% (n = 46) targeting Social and Community Factors (SCF), Living and Working Conditions (LWC) and Wider Conditions (WC) respectively. Conversely, 60% of causes were spread across the LWC and WC, with 16.4% regarded as ILF. Physical activity-, weight management-, and health improvement- programmes were most frequently implemented by LAs. There is a stark mismatch between LA actions on obesity and its perceived causes. Given that LAs acknowledge the complex aetiology of obesity, an equally comprehensive approach should be implemented in the future.

Methods of measuring associations between the Retail Food Environment and weight status: Importance of classifications and metrics.

Despite considerable research, evidence supporting associations between the 'Retail Food Environment' (RFE) and obesity remains mixed. Differences in the methods used to measure the RFE may explain this heterogeneity. Using data on a large (n = 10,111) sample of adults from the Yorkshire Health Study (UK), we modelled cross-sectional associations between the RFE and weight status using (i) multiple definitions of 'Fast Food', 'Convenience' and 'Supermarkets' and (ii) multiple RFE metrics, identified in a prior systematic review to be common in the literature. Both the choice of outlet definition and the choice of RFE metric substantively impacted observed associations with weight status. Findings differed in relation to statistical significance, effect sizes, and directions of association. This study provides novel evidence that the diversity of RFE measurement methods is contributing to heterogeneous study findings and conflicting policy messages. Greater attention is needed when selecting and communicating RFE measures in research.

A systematic review employing the GeoFERN framework to examine methods, reporting quality and associations between the retail food environment and obesity.

This systematic review quantifies methods used to measure the 'retail food environment' (RFE), appraises the quality of methodological reporting, and examines associations with obesity, accounting for differences in methods. Only spatial measures of the RFE, such as food outlet proximity were included. Across the 113 included studies, methods for measuring the RFE were extremely diverse, yet reporting of methods was poor (average reporting quality score: 58.6%). Null associations dominated across all measurement methods, comprising 76.0% of 1937 associations in total. Outcomes varied across measurement methods (e.g. narrow definitions of 'supermarket': 20.7% negative associations vs 1.7% positive; broad definitions of 'supermarket': 9.0% negative associations vs 10.4% positive). Researchers should report methods more clearly, and should articulate findings in the context of the measurement methods employed.

Whole systems approaches to obesity and other complex public health challenges: a systematic review.

BACKGROUND: Increasing awareness of the complexity of public health problems, including obesity, has led to growing interest in whole systems approaches (WSAs), defined as those that consider the multifactorial drivers of overweight and obesity, involve transformative co-ordinated action across a broad range of disciplines and stakeholders, operate across all levels of governance and throughout the life course. This paper reports a systematic review of WSAs targeting obesity and other complex public health and societal issues, such as healthy lifestyles for prevention of non-communicable disease. METHODS: Seven electronic databases were searched from 1995 to 2018. Studies were included if there had been an effort to implement a WSA. Study selection was conducted by one reviewer with a random 20% double checked. Data extraction and validity assessment were undertaken by one reviewer and checked by a second reviewer. Narrative synthesis was undertaken. RESULTS: Sixty-five articles were included; 33 about obesity. Most examined multicomponent community approaches, and there was substantial clinical and methodological heterogeneity. Nevertheless, a range of positive health outcomes were reported, with some evidence of whole systems thinking. Positive effects were seen on health behaviours, body mass index (BMI), parental and community awareness, community capacity building, nutrition and physical activity environments, underage drinking behaviour and health, safety and wellbeing of community members, self-efficacy, smoking and tobacco-related disease outcomes. Features of successful approaches reported in process evaluations included: full engagement of relevant partners and community; time to build relationships, trust and capacity; good governance; embedding within a broader policy context; local evaluation; finance. CONCLUSIONS: Systems approaches to tackle obesity can have some benefit, but evidence of how to operationalise a WSA to address public health problems is still in its infancy. Future research should: (a) develop an agreed definition of a WSA in relation to obesity, (b) look across multiple sectors to ensure consistency of language and definition, (c) include detailed descriptions of the approaches, and (d) include process and economic evaluations.

Addressing childhood obesity in low-income, ethnically diverse families: outcomes and peer effects of MEND 7-13 when delivered at scale in US communities.

OBJECTIVES: Implementation of a large-scale, child weight management program in low-income, ethnically diverse communities provided an important opportunity to evaluate its effectiveness under service level conditions (i.e. provision as a primary care child weight management service). METHODS: MEND 7-13 is a community-based, multi-component, childhood obesity intervention designed to improve dietary, physical activity and sedentary behaviors. It comprises twice weekly sessions for 10 consecutive weeks (35 contact hours) and is delivered to groups of children and accompanying parents/caregivers. The evaluation used an uncontrolled, repeated measures design. Overall, 3782 children with overweight or obesity attended 415 MEND 7-13 programs in eight US states, of whom 2482 children (65.6%) had complete data for change in zBMI. The intervention targeted low-income, ethnically diverse families. Changes in anthropometric, cardiovascular fitness and psychological outcomes were evaluated. A longitudinal multivariate imputation model was used to impute missing data. Peer effects analysis was conducted using the instrumental variables approach and group fixed effects. RESULTS: Mean changes in BMI and zBMI at 10 weeks were -0.49 kg/m2 (95% CI: -0.67, -0.31) and -0.06 (95% CI: -0.08, -0.05), respectively. Benefits were observed for cardiovascular fitness and psychological outcomes. Mean peer reduction in zBMI was associated with a reduction in participant zBMI in the instrumental variables model (B = 0.78, P = 0.04, 95% CI: 0.03, 1.53). Mean program attendance and retention were 73.9% and 88.5%, respectively. CONCLUSION: Implementing MEND 7-13 under service level conditions was associated with short-term improvements in anthropometric, fitness and psychological indices in a large sample of low-income, ethnically diverse children with overweight and obesity. A peer effect was quantified showing that benefits for an individual child were enhanced, if peers in the same group also performed well. To our knowledge, this is the first US study to evaluate outcomes of an up-scaled community-based, child weight management program and to show positive peer effects associated with participation in the intervention.

How has big data contributed to obesity research? A review of the literature.

There has been growing interest in the potential of 'big data' to enhance our understanding in medicine and public health. Although there is no agreed definition of big data, accepted critical components include greater volume, complexity, coverage and speed of availability. Much of these data are 'found' (as opposed to 'made'), in that they have been collected for non-research purposes, but could include valuable information for research. The aim of this paper is to review the contribution of 'found' data to obesity research to date, and describe the benefits and challenges encountered. A narrative review was conducted to identify and collate peer-reviewed research studies. Database searches conducted up to September 2017 found original studies using a variety of data types and sources. These included: retail sales, transport, geospatial, commercial weight management data, social media, and smartphones and wearable technologies. The narrative review highlights the variety of data uses in the literature: describing the built environment, exploring social networks, estimating nutrient purchases or assessing the impact of interventions. The examples demonstrate four significant ways in which 'found' data can complement conventional 'made' data: firstly, in moving beyond constraints in scope (coverage, size and temporality); secondly, in providing objective, quantitative measures; thirdly, in reaching hard-to-access population groups; and lastly in the potential for evaluating real-world interventions. Alongside these opportunities, 'found' data come with distinct challenges, such as: ethical and legal questions around access and ownership; commercial sensitivities; costs; lack of control over data acquisition; validity; representativeness; finding appropriate comparators; and complexities of data processing, management and linkage. Despite widespread recognition of the opportunities, the impact of 'found' data on academic obesity research has been limited. The merit of such data lies not in their novelty, but in the benefits they could add over and above, or in combination with, conventionally collected data.

Is adolescent body mass index and waist circumference associated with the food environments surrounding schools and homes? A longitudinal analysis.

BACKGROUND: There has been considerable interest in the role of access to unhealthy food options as a determinant of weight status. There is conflict across the literature as to the existence of such an association, partly due to the dominance of cross-sectional study designs and inconsistent definitions of the food environment. The aim of our study is to use longitudinal data to examine if features of the food environment are associated to measures of adolescent weight status. METHODS: Data were collected from secondary schools in Leeds (UK) and included measurements at school years 7 (ages 11/12), 9 (13/14), and 11 (15/16). Outcome variables, for weight status, were standardised body mass index and standardised waist circumference. Explanatory variables included the number of fast food outlets, supermarkets and 'other retail outlets' located within a 1 km radius of an individual's home or school, and estimated travel route between these locations (with a 500 m buffer). Multi-level models were fit to analyse the association (adjusted for confounders) between the explanatory and outcome variables. We also examined changes in our outcome variables between each time period. RESULTS: We found few associations between the food environment and measures of adolescent weight status. Where significant associations were detected, they mainly demonstrated a positive association between the number of amenities and weight status (although effect sizes were small). Examining changes in weight status between time periods produced mainly non-significant or inconsistent associations. CONCLUSIONS: Our study found little consistent evidence of an association between features of the food environment and adolescent weight status. It suggests that policy efforts focusing on the food environment may have a limited effect at tackling the high prevalence of obesity if not supported by additional strategies.

Examining the validity and utility of two secondary sources of food environment data against street audits in England.

BACKGROUND: Secondary data containing the locations of food outlets is increasingly used in nutrition and obesity research and policy. However, evidence evaluating these data is limited. This study validates two sources of secondary food environment data: Ordnance Survey Points of Interest data (POI) and food hygiene data from the Food Standards Agency (FSA), against street audits in England and appraises the utility of these data. METHODS: Audits were conducted across 52 Lower Super Output Areas in England. All streets within each Lower Super Output Area were covered to identify the name and street address of all food outlets therein. Audit-identified outlets were matched to outlets in the POI and FSA data to identify true positives (TP: outlets in both the audits and the POI/FSA data), false positives (FP: outlets in the POI/FSA data only) and false negatives (FN: outlets in the audits only). Agreement was assessed using positive predictive values (PPV: TP/(TP + FP)) and sensitivities (TP/(TP + FN)). Variations in sensitivities and PPVs across environment and outlet types were assessed using multi-level logistic regression. Proprietary classifications within the POI data were additionally used to classify outlets, and agreement between audit-derived and POI-derived classifications was assessed. RESULTS: Street audits identified 1172 outlets, compared to 1100 and 1082 for POI and FSA respectively. PPVs were statistically significantly higher for FSA (0.91, CI: 0.89-0.93) than for POI (0.86, CI: 0.84-0.88). However, sensitivity values were not different between the two datasets. Sensitivity and PPVs varied across outlet types for both datasets. Without accounting for this, POI had statistically significantly better PPVs in rural and affluent areas. After accounting for variability across outlet types, FSA had statistically significantly better sensitivity in rural areas and worse sensitivity in rural middle affluence areas (relative to deprived). Audit-derived and POI-derived classifications exhibited substantial agreement (p < 0.001; Kappa = 0.66, CI: 0.63-0.70). CONCLUSIONS: POI and FSA data have good agreement with street audits; although both datasets had geographic biases which may need to be accounted for in analyses. Use of POI proprietary classifications is an accurate method for classifying outlets, providing time savings compared to manual classification of outlets.