Stimulation of energy intake and growth by saccharin in rats

Rats fed wet diets containing saccharin consumed 12-14% more energy and gained 24-55% 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.