Sensitivity of ad libitum meals to detect changes in hunger. Restricted-item or multi-item testmeals in the design of preload appetite studies.

The aims of the study were to determine whether restricted single-item or multi-item testmeals are better able to detect prior changes in hunger and fullness when assessing ad libitum eating behaviour. Thirty male participants were given a low- (L(E), 0.5 MJ) or high-energy (H(E), 4.0 MJ) breakfast preload designed to induce or suppress hunger, followed 3h later by a restricted-item (R(I)) or multi-item (M(I)) testmeal. The R(I) testmeal comprised pasta+meat sauce, whilst the M(I) testmeal comprised pasta+meat sauce plus bread, chicken, ham, cheese, salad, cake and fruit. The four conditions were (i) L(E)/R(I); (ii) L(E)/M(I); (iii) H(E)/R(I); (iv) H(E)/M(I). Visual analogue scales (VAS) were used to rate appetite sensations and EI was measured at the lunch testmeal. As expected, increasing the energy content of the preload significantly altered VAS ratings and decreased EI at the testmeal. Following both L(E) and H(E) breakfasts, EI was lower at the R(I) (L(E)=4566 kJ, H(E)=3583 kJ) compared with the M(I) (L(E)=6142 kJ, H(E)=5149 kJ) testmeal. However, the compensatory decrease in EI in response to the H(E) breakfast was not significantly greater at the R(I) testmeal (R(I): -983 kJ, 28.1% compensation; M(I): -993 kJ, 28.4% compensation). In preload studies measuring EI, increasing the variety of an ad lib testmeal may not decrease the sensitivity to detect changes in hunger and fullness.