Effect of ultra-processed-rich versus ultra-processed-free preload meals at high and low energy density on ad libitum energy intake: a randomized crossover trial.

Ultraprocessed food (UPF) consumption leads to lower satiation under ad libitum conditions compared with less processed foods, with energy density (ED) proposed as a key mediator. However, studies using fixed-energy portions are needed to clarify the impact of UPF on satiety. This randomized, 2x2 crossover trial evaluated the effects of preload meals differing in processing level (0% vs. ≥80% of energy from UPF) and ED (≤1.2 vs. ≥2.0kcal/g) on ad libitum energy intake and appetite in adults. Each intervention lasted one day and included two preload meals (breakfast and lunch). The primary outcome was the difference on ad libitum dinner (ED 1.7kcal/g; 20% UPF) energy intake at the end of each day, compared to the same dinner in a control day (ΔEI). Appetite ratings were measured 15 times per day, using visual analogue scales. Data were analyzed using mixed-effects linear models. Nineteen individuals (9 females, mean age 22.1±3.2 years, mean BMI 23.5 ± 2.7kg/m2) were included. There were no main effects or interaction effects of processing and ED on ΔEI (UPF: -24.5, 95%CI: [-87; 38] kcal; ED: -41.6, [-104; 20.9]kcal). High-ED preload meals resulted in small increases in hunger (3.61, [1.6; 5.6]mm), satisfaction (2.8, [0.5; 5.0]mm), and capacity to eat (2.6, [0.3; 4.8]mm), and lower fullness (-5.3, [-7.5; -3.1]mm) compared with the low-ED. Capacity to eat remained higher after dinner in the high-ED condition (3.31, [0.41; 6.21]mm). Food processing did not affect short-term satiety. Acute differences in ED produced small changes in subjective appetite ratings without affecting subsequent energy intake.