Impact of the Eating Rate of Ultra-processed Foods on Dietary Intake Behavior and Metabolic Responses

Rationale: Consumption of industrially processed foods has been associated with obesity and related adverse health outcomes. If this reflects a causal relationship, it is unknown what attributes or properties of industrially processed foods might drive this association. Extensive research has shown that foods consumed with a texture-derived slow eating rate (ER) are consumed in smaller amounts relative to foods consumed with a fast ER. ER has been suggested as one of the mechanisms why (ultra-)processed foods (with a fast ER) may promote excess in calorie intakes. We will therefore test the hypothesis that ER moderates energy intakes from ultra-processed foods.

Objective: The primary objective of this study is to determine the effect of ER of ultra-processed food diets (UPF slow ER vs UPF fast ER) on ad libitum energy intake (kcal/day) across a two week period. The secondary objectives are to compare body composition and metabolic changes that occur when on a 14 day diet of ultra-processed foods with either a slow or a fast ER.

Study design: We will conduct a balanced-order, block randomized controlled cross-over trial with 2 treatment arms, to determine the effect of ER of ultra-processed food diets (UPF fast ER vs UPF slow ER) on ad libitum energy intake (kcal) across a two week period. The study will have a run-in period to determine habitual dietary habits (baseline) and a washout period (14 days) between treatments to prevent carry-over effects. All participants will receive both treatments and are their own control (within subject design).

Study population: 39 healthy, non-smoking, adults between 21-50 years old and with a BMI between 21-27 kg/m2 will be included.

Intervention: The two treatments are 1) a 14-days ultra-processed, slow ER diet, and 2) a 14-days ultra-processed, fast ER diet. The ad libitum meal menus are matched for energy density (kcal/g), liking (hedonic range), and level of processing, but different in textural characteristics known to influence ER. During the treatment periods participants eat all of their main meals at the research site on weekdays. Participants receive pre-packed meals to consume at home for the weekends. Meals are served ad-libitum, presented in portions that are > 200% of a regular portion size. Participants are asked to eat from each meal until they feel comfortably full. Food (gram) and energy (kcal) consumed will be recorded at the level of the meal, the day and week of the interventions.