A method for managing the weight of a subject having an associated predefined target weight, comprises deriving a target energy balance and computing the realized energy balance (303) from collected information (301, 302). It further comprises determining a weight reduction plan (304) comprising a sequence of at least two phases, representing a corresponding sequence of successive time intervals, one phase representing a time interval having an end time associated with an end time of the target period. It involves assigning to each successive phase a distinct set of phase targets comprising at least one phase target relating to food intake of the subject, physical activity of the subject, or target body weight of the subject, such that according to a simulation model of the relation between energy intake, physical activity, and body weight, each phase fulfills the constraint that the respective assigned set of phase targets can be achieved.