A Critical Review of the Science on “Highly” Processed Food Intake and Body Weight

There is increasing consideration of food processing and formulation in setting dietary guidance at the state, federal and global levels to manage obesity and other health conditions. However, the supporting evidence base is highly controversial. This stems, in part, from the lack of a widely accepted definition of highly- or ultra-processed foods and beverages (HPFB) and evidence that published definitions hold different predictive health risks. The preponderance of evidence linking food processing and formulation practices to health outcomes is drawn from observational studies. This literature generally suggests intake of HPFB is associated with greater obesity risk. However, a critical assessment indicates the associations are weak and inconsistent. More recently, a number of randomized controlled trials have been published based on educational, community-based dietary and metabolic ward feeding interventions. Metabolic ward trials involved small samples, short-term assessment and ecologically questionable comparisons. They reported no changes of appetite, and only transient shifts in food intake. The community-based trials, generally have high attrition rates and used no objective measure of dietary compliance with the intervention. They reveal implementation of interventions to moderate HPFB intake is often not achieved. No community-based trial has observed weight gain on the high HPFB treatment arm and only half report a significant group weight differential. Among all trials, intake of HPFB has led to increased, no change and decreased body weight. To-date they do not adequately support a causal relationship between HPFB intake and obesity risk. Given the tangible likely adverse effects of eliminating HPFB from the diet, such as increased food-borne illness, greater food waste, as well as decreased diet quality, increased food cost and reduced convenience, especially for segments of the population least able to tolerate such changes, dietary guidance based solely on the HPFB concept is, presently, not in the public's best interest.