CALORIC DENSITY AFFECTS FOOD HOARDING AND INTAKE BY SIBERIAN HAMSTERS

Siberian hamsters respond to food deprivation or restriction by increa sing their food hoarding and do so proportionately to the degree of bo dy mass (fat) loss. These data suggest that Siberian hamsters integrat e their internally stored energy as body fat with their externally sto red energy as hoarded food such that when internal energy stores are d ecreased, external stores are increased. The purpose of the present ex periments was to test whether the caloric value of the food hoard is r egulated. This was accomplished by challenging the hamsters with diets of varying caloric density and assessing whether their hoarded food i s changed accordingly. Specifically, in Experiment 1 hamsters were swi tched from the control food pellets to a diet where the caloric densit y was increased by creating a high fat diet (HFD). In Experiment 2, th e caloric density of the control diet was decreased by diluting it wit h cellulose such that 25% and 50% (kcal/wt) reduced calorie diets (RCD s) were created. HFD-fed hamsters decreased their food hoarding, incre ased their body mass, and decreased the grams of food eaten, but not e nough to compensate exactly for the increased caloric density of the d iet. When refed the control diet, food hoarding increased to pre-HFD l evels as body mass and food intake decreased. RCD feeding resulted in caloric density-dependent effects on all measures. Food hoarding and i ntake (grams and calories) increased when hamsters were given the 25% RCD and did so to an even greater degree when given the 50% RCD. Thus, Siberian hamsters responded to increases or decreases in the caloric density of their food by attempting to regulate the number of calories hoarded and eaten; however, the adjustments in food hoarding: 1) were not precise, 2) were largely opposite of food intake, 3) tended to be inversely related to body mass and 4) were caloric density dependent.