D-Psicose (D-ribo-2-hexulose), a C-3 epimer of D-fructose, is present in small quantities in commercial carbohydrate complexes and agricultural products. We have previously reported that D-psicose supplements in diets suppressed hepatic lipogenic enzyme activity The lower fat accumulation in rats fed D-psicose may be due to lower lipogenesis in the liver. The present study examined the energy available in D-psicose for rat growth. Male Wistar rats received 7 g daily of a basal diet to which fixed amounts of sucrose, D-fructose, or D-psicose (0.5-2.0 g) were added for 20 d. Body weight gain and body energy gain increased with increases in sucrose and D-fructose, but not with D-psicose. One gram of sucrose, D-fructose, and D-psicose produced a net energy gain of 2.29, 1.76, and 0.007 kcal, respectively. The efficiency of energy deposition from D-psicose was 0.3% that of sucrose. The energy value of D-psicose was effectively zero. These results suggest that D-psicose is a rare sugar providing zero energy that may be useful in sweeteners for obese people as an aid for weight reduction.