Sixteen 22-month-old male Sprague Dawley rats (579 6 47 g, Charles River, L’Arbresle, France) were brought to our central animal facility and housed for a 2-week accli- matization period in individual metabolic cages that allowed the measurement of food intake and the collection of urine and feces. These cages were maintained at a constant tem- perature (21 6 18C) and humidity, on a 12-hour light/dark cycle. The rats were given free access to standard laboratory chow (16% protein, 3% fat, 60% carbohydrate, 12% water, vitamins, and minerals) supplying 290 kcal/100 g (A04; Safe, Villemoisson-sur-Orge, France), and water. During the first 2-week period (Figure 1), food intake was measured daily as was the weight of chow ingested (weight of chow given – weight of chow left in the bowl the day after). The rats ingested a mean of 23 6 4 g/day of chow, that is, 67 kcal/day. This amount of energy intake became our refer- ence for determining the nutritional goal for the period of enteral feeding.