A method, an apparatus, and a system for estimating body fat that are capable of measuring a portion of an abdominal outline by a simple method are provided. A method of estimating the body fat according to the present embodiments includes: a step of obtaining orientation information and motion information of the apparatus itself； a step of calculating a portion of an abdominal outline by a control unit based on the orientation information and the motion information； and a step of estimating, based on the portion of the abdominal outline, at least one of a visceral fat area and a subcutaneous fat area of the abdominal cross-section.
