Homeostatic Responses to Palatable Food Consumption in Satiated Rats

Objective: Energy intake is regulated by overlapping homeostatic and hedonic systems. Consumption of palatable foods has been implicated in weight gain, but this assumes that homeostatic control systems do not accurately detect this hedonically driven energy intake. This study tested this assumption, hypothesizing that satiated rats would reduce their voluntary food intake and maintain a stable body weight after consuming a palatable food.

Methods: Lean rats or rats previously exposed to an obesogenic diet were schedule-fed with fixed or varying amounts of palatable sweetened condensed milk (SCM) daily, and their voluntary energy intake and body weight were monitored.

Results: During scheduled feeding of SCM, rats voluntarily reduced bland food consumption and maintained a stable body weight. This behavior was also seen in rats with access to an obesogenic diet and was independent of the predictability of SCM access. However, lean rats offered large amounts of SCM showed an increase in total energy intake. To test whether a nutrient deficiency drove this under-compensatory behavior, SCM was enriched with protein. However, no effect was seen on voluntary energy intake.

Conclusions: In schedule-fed rats, compensatory reductions in voluntary energy intake were seen, but under-compensation was observed if large amounts of SCM were consumed.