A body composition change prediction device acquires a measured acetone concentration measuring acetone excreted from a user, acquires current body composition information and past body composition information of the user, computes a prediction value predicting the body composition information at a given future point in time based on information relating to the body composition of the user, and determines a fat burning style of the user based on the acetone concentration and the current body composition information. The body composition change prediction device weights the prediction value based on a weight, the weight being set according to the burning style and being a greater weight the higher the measured ketone body concentration, and outputs information according to the weighted prediction value.
