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Monell Chemical Senses Center, Philadelphia, PA 19104-3308
Rats fed wet diets containing saccharin consumed 1214% more energy and gained 2455% more weight than rats fed the same diets without saccharin. Saccharin-induced stimulation of intake was usually not so pronounced during the first week as during subsequent weeks of each experiment. Similar results were obtained using diets high in starch and fat. However, these effects could be obliterated by simply exposing the rats to unsweetened (plain) diet or to saccharin in water for several days before the sweetened diets were introduced. Furthermore, although stimulation of intake by saccharin was observed with diets containing 80% water, no such effect was observed with a diet containing 60% water. Rats given low-energy sweetened water in addition to their 80% water diet consumed substantially more fluid but not more or less energy than rats given unsweetened water. Preference tests suggest that saccharin increases diet palatability only very slightly; this finding is one of several observations suggesting that stimulation of intake by saccharin cannot be interpreted in terms of increased diet palatability. These results suggest that dietary hyperphagia results from the interaction between innate and learned responses to the taste of foods. Osmotic factors did not seem to exert a major influence in these experiments.
KEY WORDS: sweet taste rats saccharin learning energy intake hyperphagia
1 This work was supported by a National Science Foundation grant (BNS 87-19309), National Institutes of Health support (Biomedical Research Support Grant RR05825-07) and the Monell Chemical Senses Center.
Manuscript received 6 March 1989. Revision accepted 25 September 1989.