Research
Mixed
Natural experiments with weaker study designs (cross-sectional, case-only) are more likely to report positive associations with interventions than those with strong designs (longitudinal with comparison groups).
Be skeptical of positive findings from single-site, cross-sectional studies of policy changes. Prioritize longitudinal studies with comparison groups for evidence-based decision making.
StrongSupportsHIGH confidence
Studies varied widely in the strength of their design and studies with weaker designs were more likely to report associations in the positive direction.
Why this rating
Directly stated in the summary of the review.
Source
Impact of policy and built environment changes on obesity‐related outcomes: a systematic review of naturally occurring experiments
Stephanie L. Mayne et al. · Obesity Reviews · 2015
DOI 10.1111/obr.12269
systematic_reviewCited 299×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Regulatory bans or restrictions on unhealthy foods (e.g., trans fat bans, SSB bans) and mandates for healthier options in institutional settings (schools) significantly improve dietary quality and reduce consumption of target nutrients, whereas menu labeling alone has negligible impact on purchasing behavior.Good
- Built environment interventions that improve active transportation infrastructure (bike lanes, trails, light rail) increase process outcomes (cycling rates, walking volume) but do not consistently increase total physical activity or reduce BMI.Good
Related findings · Mixed
- Bariatric surgery (VSG and RYGB) is the most effective and sustainable treatment for obesity, producing marked and sustained weight loss that non-surgical interventions cannot match.Strong
- Severely protein-deficient diets (2–3% energy) induce lean body mass loss and metabolic imbalance, whereas adequate protein intake (0.66 g/kg/d minimum) is a prerequisite for maintaining muscle, bone, and physiological function.Strong
- For patients with Class III obesity (BMI >39.9 kg/m2), metabolic bariatric surgery (MBS) is significantly more effective than any currently approved medication, with BilioPancreatic Diversion (BPD) showing the highest estimated weight loss.Strong
This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →