An information processing device configured to estimate a digestion rate of food ingested by a user, the information processing device comprising: a first receiver configured to receive, from a heart rate signal measuring device carried by the user, a plurality of heart rate signal information items measured at predetermined time intervals; a second receiver configured to receive information of meal start time and meal end time of the user; a characteristic amount calculator configured to: specify a heart rate of the user at the meal start time from the plurality of heart rate signal information items, calculate, by using the plurality of heart rate signal information items, a primary approximate straight line obtained by approximating a profile indicating decrease of a heart rate of the user included in a trend of the heart rate after an end of a meal, the trend indicating that the heart rate increases and subsequently decreases, and estimate a time point indicating the same value as the heart rate at the meal start time on the calculated primary approximate straight line as the digestion end time indicating a time when the digestion of the food ends; and a digestion rate estimator configured to calculate the digestion rate by calculating a ratio of a length of a time period from the meal end time to a current time with respect to a length of a time period from the meal end time to the digestion end time; and an information presenter configured to present information on a service according to the calculated digestion rate to the user. a first receiver configured to receive, from a heart rate signal measuring device carried by the user, a plurality of heart rate signal information items measured at predetermined time intervals; a second receiver configured to receive information of meal start time and meal end time of the user; a characteristic amount calculator configured to: specify a heart rate of the user at the meal start time from the plurality of heart rate signal information items, calculate, by using the plurality of heart rate signal information items, a primary approximate straight line obtained by approximating a profile indicating decrease of a heart rate of the user included in a trend of the heart rate after an end of a meal, the trend indicating that the heart rate increases and subsequently decreases, and estimate a time point indicating the same value as the heart rate at the meal start time on the calculated primary approximate straight line as the digestion end time indicating a time when the digestion of the food ends; and specify a heart rate of the user at the meal start time from the plurality of heart rate signal information items, calculate, by using the plurality of heart rate signal information items, a primary approximate straight line obtained by approximating a profile indicating decrease of a heart rate of the user included in a trend of the heart rate after an end of a meal, the trend indicating that the heart rate increases and subsequently decreases, and estimate a time point indicating the same value as the heart rate at the meal start time on the calculated primary approximate straight line as the digestion end time indicating a time when the digestion of the food ends; and a digestion rate estimator configured to calculate the digestion rate by calculating a ratio of a length of a time period from the meal end time to a current time with respect to a length of a time period from the meal end time to the digestion end time; and an information presenter configured to present information on a service according to the calculated digestion rate to the user.