Reduction of dietary energy density reduces body mass regain following energy restriction in female mice

Restriction of energy intake induces a loss of body mass that is often regained when the restriction ends. We aimed to determine whether dietary energy density (independent of macronutrient composition) modulates postrestriction regain of body mass. Fifteen female mice consumed ad libitum a standard rodent diet (with 20% added cellulose). They were then subjected to a 20% energy restriction on this diet for 10 d. Following restriction, mice consumed ad libitum the same diet with either 0 or 40% added cellulose. The study utilized a crossover design so all mice consumed both diets. Body temperature, physical activity, and digestibility were all lower when consuming the 40% cellulose diet (P < 0.001). Mice regained less mass (9%) when consuming the 40% than the 0% cellulose diet, because net energy intake was reduced by 26% (P < 0.001), despite having a greater gross energy intake (P < 0.001) (29%). To test whether there might be a constraint on intake and digestibility of the 40% cellulose diet, 20 different female mice consumed this diet at room temperature and were then transferred to the cold (7°C) to determine whether they would increase intake of this diet in response to increased energy demands. It took up to 5 d after transfer for body mass, food intake, and digestibility to increase. This suggests a digestion constraint might have limited intake of the low-energy density diet immediately following restriction. Modulation of dietary energy density in the postrestriction phase may be a valuable strategy for maintaining mass loss achieved on energy-restricted diets.