Part 6: WSA Systematic Review of Reviews
Strand 4: Evidence for a Whole Systems Approach to Obesity
Video
Learning Objectives
After watching this section, you should be able to:
- Describe the methodology and findings of the systematic review of reviews on whole systems approaches to obesity
- Identify the three types of review found in the global WSA literature
- Explain the limitations of the current evidence base, including the dominance of process evaluations and limited long-term follow-up data
Key Points
- A global systematic review of reviews identified 8 articles from an initial search of over 20,000 records, screened down through removal of duplicates and application of eligibility criteria
- Three review types were identified: (1) reviews evaluating WSA implementation (e.g., Bagnall, Bleach, Safford); (2) reviews drawing on evidence to present a model, theory, or framework; (3) reviews using systems dynamic models, causal loop diagrams, and agent-based models
- Evaluations have been mainly process evaluations, relying on qualitative methods such as interviews and focus groups; few studies use quantitative approaches to measure system-level change
- Where outcomes were reported, WSA have shown some success in influencing BMI, BMI z-scores, reducing sugary drink intake, and increasing physical activity
- Few studies include long-term follow-up — a recognised limitation given the time required for systemic change to produce measurable population-level effects
- Public and service user involvement has not been widely reported in the literature; Northern Ireland has responded by working with people with lived experience of healthy weight within the Belfast City Council area
Further Reading
- A whole systems approach to obesity prevention: a rapid synthesis of evidence — the full IPH report containing the global systematic review of reviews discussed in this video, along with its three review typologies (Breslin et al., 2023)
- Bagnall AM et al. (2019). Whole systems approaches to obesity and other complex public health challenges: a systematic review. BMC Public Health, 19, 8. — one of the eight review articles included in the systematic review of reviews; open access
- Bleich SN et al. (2013). Systematic review of community-based childhood obesity prevention studies. Pediatrics, 132(1), e201–e210. — a second review article included in the systematic review of reviews, focusing on community-based childhood obesity prevention
- NIHR PHIRST: Getting RREAL about implementation of a WSA to obesity prevention in Northern Ireland — the Northern Ireland process evaluation project; an example of the qualitative, process-focused evaluation approaches described in this video
Knowledge Check
Complete the questions below before moving on.
The systematic review of reviews on whole systems approaches to obesity found that evaluations were mainly process evaluations. What does this tell us about the nature of the evidence base?
The correct answer is the evidence has relied heavily on qualitative methods, with very few quantitative studies. Because evaluations have predominantly been process evaluations, the evidence base draws mainly on qualitative approaches — interviews, focus groups, and stakeholder engagement — with practitioners involved in implementing whole systems approaches. Few studies have measured system-level change quantitatively, and long-term follow-up data remain limited given the time needed for whole systems approaches to produce measurable population-level outcomes.
- False — the whole systems approach is explicitly a real-world, community- based framework; laboratory-based evidence is not part of this evidence base.
- False — randomised controlled trials are uncommon in whole systems research; the process evaluation focus means qualitative methods predominate.
- False — while some whole systems approaches have shown impact on BMI and BMI z-scores, the review does not report large population-level BMI reductions as a consistent finding.
- True