[PROBLEMS] To prevent the progression occurrence or ameliorate a condition of obesity, diabetes or metabolic syndrome. [MEANS FOR SOLVING PROBLEMS] Disclosed is a composition comprising D-psicose and/or a derivative thereof as an active ingredient, which, when a hydrocarbon and/or a saccharide having D-fructose as a part of the structure or containing D-fructose therein is ingested, can prevent the increase in blood D-fructose level, preferably can also prevent the increase in blood D-glucose level simultaneously. The D-psicose may be a mixture of D-psicose and D-fructose. The composition can be used in any form selected from the group consisting of a sweetening agent, a seasoning agent, a food additive, a food material, a beverage/food, a health beverage/food, a pharmaceutical and a feeding stock. Also disclosed is use of D-psicose for the prevention of the increase in blood D-fructose level, preferably also for the prevention of the increase in blood D-glucose level simultaneously, by administering D-psicose when a hydrocarbon and/or a saccharide having D-fructose as a part of the structure or containing D-fructose therein is ingested.
