^*Ingestive Behavior Research Center and Department of Psychological Sciences, Purdue University, West Lafayette, Indiana

Correspondence: Terry L. Davidson, Department of Psychological Sciences, Purdue University, 703 Third Street, West Lafayette, Indiana 47907. E-mail: davidson@psych.purdue.edu

^**The costs of publication of this article were defrayed, in part, by the payment of page charges. This article must, therefore, be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Received 6 July 2004; Accepted 23 December 2004.

Abstract

Objective: To determine the effects of food viscosity on the ability of rats to compensate for calories in a dietary supplement.

Research Methods and Procedures: In a series of four experiments, rats consumed dietary supplements equated for caloric and nutritive content but differing in viscosity. Experiments 1 to 3 examined the ability of the rats to compensate for the calories consumed in low- compared with high-viscosity premeals by reducing intake of a subsequent test meal. Caloric compensation was assessed with a wide range of premeal viscosity levels and with two different non-nutritive thickening agents. Experiment 4 assessed the effects of consuming daily a low-viscosity compared with an equicaloric high-viscosity dietary supplement on longer term body weight gain.

Results: Consuming a lower viscosity premeal was followed by significantly more caloric intake (i.e., less caloric compensation) compared with consuming premeals with higher viscosity levels. This effect was not specific to one thickening agent. Furthermore, rats given a low-viscosity supplement daily gained significantly more weight over a 10-week period compared with rats given a high-viscosity supplement.

Discussion: The results of these experiments suggest that food viscosity may be an important determinant of short-term caloric intake and longer term body weight gain.