Traffic light diets for childhood obesity: disambiguation of terms and critical review of application, food categorization, and strength of evidence

(This article has been accepted for publication in Current Developments in Nutrition published by Oxford University Press.) Traffic light labeling (TLL) of foods is a strategy often included in multicomponent behavioral interventions (MBI) for childhood obesity. TLLs categorize foods as ‘green’ (no restrictions); ‘yellow’ (moderation); and ‘red’ (consume minimally). The body of research investigating the effects of TLL conflates the labeling itself with MBIs that include TLL as one component. For instance, the Academy of Nutrition and Dietetics’ Evidence Analysis Library gave traffic light diets Grade I evidence for pediatric weight management. Yet, whether the term traffic light diet referenced TLL in isolation or as part of an MBI was ambiguous. Herein we evaluate the evidence supporting TLL for childhood obesity as a standalone treatment and identify areas requiring further research. No articles from a PubMed search for TLL and weight-related outcomes tested TLL in isolation. One article was identified through reference lists that tested TLL mostly in isolation, which observed no significant differences between groups. TLL definitions and categorizations vary across studies and contexts, using average calories in categories of foods, energy density, or specific ingredients to determine labeling. Systematic reviews generally conclude TLL-based approaches affect food selection and consumption, but none studied obesity-related outcomes. We believe the evidence supports that: 1) there is a lack of standardization regarding TLL food classifications; 2) the term “traffic light diet” is inconsistently used to mean intensive lifestyle programs or TLL itself; and 3) there is insufficient evidence to understand the effects of TLL as an isolatable factor for childhood obesity. Importantly, limited evidence about TLL does not mean it is ineffective; TLL has been incorporated into successful childhood obesity intervention programs, but the unique causal contribution of TLL remains uncertain. Standardized definitions of traffic light labels for categorizing foods and trials with TLL alone are needed to test direct impacts of TLL on obesity-related outcomes.