Effects of physical state (liquid-solid) of foods on food intake: procedural and substantive contributions

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Abstract
Two types of procedures are described for the study of the effects of food attributes on food intake. One is concurrent evaluation in which the attribute is placed in the food, and the amount consumed is measured. The other is the preloading paradigm in which a food containing the attribute is given before a test meal and intake of the test meal is measured. From our work with both types of procedure in which we used foods in both solid and liquefied form, we conclude that the effects of food attributes on intake will differ depending on which procedure is used. Concurrent evaluation is recommended when the time course of the attribute is short-lived (few seconds to a minute). Preloading is the procedure of choice when the attribute's effect is longer-lasting (several minutes to hours). When the same food was served in either solid or liquefied form, there was no difference in intakes of the two versions, but for liquefied form, the rate of consumption was faster, and meal duration was shorter, than for the solid. When a completely liquefied preload (soup) was given, intake in the following test meal was less for the same caloric load than when the preload was only partly in liquid form. Liquefied foods may be more efficient in producing satiety, as measured by food intake reduction, than solids. Because the two preloads were different across dimensions other than solid-liquid, more investigation of these other dimensions is needed.