Traffic Light Diets Per Se Have Limited Evidence for Effectiveness on Childhood Obesity: A Review

Abstract

Abstract Objectives The “traffic light diet” (TLD; or “stop light diet” among other names) categorizes foods into ‘green’, ‘yellow’, or ‘red’ groups to consume without restriction, in moderation, or minimally, respectively. It is often a component of childhood interventions targeting weight-related outcomes. The Academy of Nutrition and Dietetics Evidence Analysis Library assigned TLDs Grade I evidence in 2006 for pediatric weight management, but none of the studies reviewed tested the TLD in isolation. We conducted a review of the effect of TLDs on obesity-related outcomes in children and definitions among different implementations of TLDs. Methods We searched PubMed up to September 2019 for interventions using the TLD with obesity-related anthropometric outcomes. Studies were screened in duplicate, and treatment characteristics extracted. Additional studies were identified by screening references. Using a convenience sample of texts from the original TLD creators, Indiana University vending, a new pediatric weight loss app, and an online resource, we assessed how definitions of TLDs compare. Results Our search identified 386 abstracts, 5 of which were interventions that included the TLD and weight-related outcomes. Three of these were randomized controlled trials, and none studied the TLD in isolation outside of multicomponent interventions. We then focused on 4 foundational TLD articles that were repeatedly cited. One of these isolated the TLD from the multicomponent intervention but found no statistical effect of the diet or interaction of diet with other factors for weight-related outcomes. In the sample of TLD implementations, substantial differences were apparent in how foods were classified among green, yellow, and red groups, such as avocados, nuts, figs/fig cookies, and peanut butter. Conclusions There is insufficient evidence supporting TLDs as a unique, isolatable factor in improving weight-related outcomes in children. This does not necessarily mean that TLDs are ineffective, as they have been incorporated into successful interventions. A standardization of TLD definitions (consistently categorizing foods and whether the term ‘TLD’ is meant to include other components of an intensive lifestyle intervention) is needed to make comparisons of effectiveness going forward. Funding Sources The authors received no funding for this specific work.