Caloric density affects food hoarding and intake by Siberian hamsters

Siberian hamsters respond to food deprivation or restriction by increasing their food hoarding and do so proportionately to the degree of body mass (fat) loss. These data suggest that Siberian hamsters integrate their internally stored energy as body fat with their externally stored energy as hoarded food such that when internal energy stores are decreased, external stores are increased. The purpose of the present experiments was to test whether the caloric value of the food hoard is regulated. This was accomplished by challenging the hamsters with diets of varying caloric density and assessing whether their hoarded food is changed accordingly. Specifically, in Experiment 1 hamsters were switched from the control food pellets to a diet where the caloric density was increased by creating a high fat diet (HFD). In Experiment 2, the caloric density of the control diet was decreased by diluting it with cellulose such that 25% and 50% (kcal/wt) reduced calorie diets (RCDs) were created. HFD-fed hamsters decreased their food hoarding, increased their body mass, and decreased the grams of food eaten, but not enough to compensate exactly for the increased caloric density of the diet. When refed the control diet, food hoarding increased to pre-HFD levels as body mass and food intake decreased. RCD feeding resulted in caloric density-dependent effects on all measures. Food hoarding and intake (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.