Perspective: A Research Roadmap about Ultra-Processed Foods and Human Health for the United States Food System: Proceedings from an Interdisciplinary, Multi-Stakeholder Workshop

Abstract

Our objective was to convene interdisciplinary experts from government, academia, and industry to develop a Research Roadmap to identify research priorities about processed food intake and risk for obesity and cardiometabolic diseases (CMD) among United States populations. We convened attendees at various career stages with diverse viewpoints in the field. We held a "Food Processing Primer" to build foundational knowledge of how and why foods are processed, followed by presentations about how processed foods may affect energy intake, obesity, and CMD risk. Breakout groups discussed potential mechanistic and confounding explanations for associations between processed foods and obesity and CMD risk. Facilitators created research questions (RQs) based on key themes from discussions. Different breakout groups convened to discuss what is known and unknown for each RQ and to develop sub-RQs to address gaps. Workshop attendees focused on ultra-processed foods (UPFs; Nova Group 4) because the preponderance of evidence is based on this classification system. Yet, heterogeneity and subjectivity in UPF classification was a challenge for RQ development. The 6 RQs were: 1) What objective methods or measures could further categorize UPFs, considering food processing, formulation, and the interaction of the two? 2) How can exposure assessment of UPF intake be improved? 3) Does UPF intake influence risk for obesity or CMDs, independent of diet quality? 4) What, if any, attributes of UPFs influence ingestive behavior and contribute to excess energy intake? 5) What, if any, attributes of UPFs contribute to clinically meaningful metabolic responses? 6) What, if any, external environmental factors lead people to consume high amounts of UPFs? Uncertainty and complexity around UPF intake warrant further complementary and interdisciplinary causal, mechanistic, and methodological research related to obesity and CMD risk to understand the utility of applying classification by degree of processing to foods in the United States.

Keywords: Nova classification system; built environment; cardiometabolic health; dietary assessment; food engineering; food environment; food science; food technology; ingestive behavior; ultra-processed food.

FIGURE 1

Timeline of select policies related to processed foods mapped onto the influx of research related to ultra-processed foods, as defined by Nova. Nova was first introduced to the research community in 2009 and then again in 2010, at the beginning of this timeline [21,22]. "Make half your grains whole" was first introducted by the 2005 DGA, but falls outside of this timeline, ∗Terms used for PudMed search: “ultra-processed food” OR ultra-processed foods” OR “ultra-processed food” OR “ultra-processed foods.” ACS, American Cancer Society; AICR, American Institute for Cancer Research; DGA, Dietary Guidelines for Americans; FDA, United States Food and Drug Administration; IARC, International Agency for Research on Cancer.

FIGURE 2

Generalized summary of how food processing categorizations capture both formulation and processes. Ultra-processed foods are created by transforming raw agricultural commodities into a final product that successively lose identity (Food Identity, purple bar) as the extent of post-harvest food processing increases (from left to right). Nutritional value is perceived to decrease in a similar fashion (Perceived Nutritional Quality, gray bar). Blue boxes represent raw agricultural commodities or foods; green boxes foods are unprocessed or minimally processed foods that would be categorized as Nova Group 1; orange boxes represent processed foods that would be categorized as Nova Group 3; and red boxes represent foods that would be categorized as Nova Group 4, ultra-processed foods, and associated ingredients.

FIGURE 3

A directed acyclic graph (DAG) depicting discussed potential direct and indirect pathways that may explain observed associations between ultra-processed food intake and increased risk for obesity and cardiometabolic disease within the United States. Created using DAGitty (v3.0, http://www.dagitty.net/). The directionality of the arrows depicts a potential relationship between variables discussed at the workshop, not necessarily consensus that a causal relationship exists or the strength of the available evidence. The yellow boxes represent exposure variables; the blue boxes represent outcomes variables or ancestors of outcome variables; and the pink boxes represent ancestor of exposure and outcome variables. The arrow in the “Ulta-Processed Food Intake” box represents the primary exposure, and the dashes in the “Cardiometabolic Health” and “Obesity” boxes represent primary outcomes.

FIGURE 4

Research Roadmap about ultra-processed foods, food processing, and human health in the context of the United States food system. UPF, ultra-processed food according to the Nova Classification System for Food Processing.

FIGURE 5

Potential pathways that the sensory, hedonic, reward, and satiety properties of ultra-processed foods promote excess energy intake and positive energy balance.