Table 2.

Summary of eight main quality concerns, n = 71 studies

	N	%
Exposure and outcome assessment
Height and weight self-reported	34	47.9
Food outlets not validated in person	62	87.3
Exposure not based on participants' address1	33	46.5
Design
Limited to obese participants or those with chronic conditions2	4	5.6
Does not account for neighborhood self-selection3	65	91.5
Analysis
Controls for variables on the causal pathway4	6	8.5
Does not account for multilevel data5	15	12.7
Does not control for age, race, sex, SES	24	33.8
Summary
Number of studies with 0 or 1 flaws	1	1.4
Number of studies with 2 or 3 flaws	40	56.3
Number of studies with >3 flaws	30	42.3

¹Studies that define exposure to food outlets based on neighborhoods or administrative units such as census tracts or zip codes

²Participants are either obese or have diseases related to obesity, suggesting the potential for selection bias

³Study does not account for neighborhood self-selection bias through either randomization, a longitudinal design combined with fixed effects regression, or causal inference methods

⁴Includes controlling for or limiting analyses to those who use the food outlet in question (ie. supermarket shoppers) or controlling for diet.

⁵Study does not use hierarchical modeling strategies, account for the clustering via adjusted standard errors, or demonstrate that clustering is limited in cases where neighborhood variables are used.