An activity monitoring device (20) includes a movement sensor (44) for producing a movement signal (118) in response to an activity level of an individual. A stationary interval timer (38) determines a stationary interval (126) during which the movement signal (118) fails to exceed a movement intensity threshold (48). When the stationary interval (126) exceeds a stationary interval threshold (50), an indicator (54, 56) alerts the individual. The activity monitoring device (20) is worn by the individual and is utilized in a weight management method. In particular, the device (20) alerts the individual whenever the stationary interval (126) exceeds the stationary interval threshold (50) so that the activity level of the individual can be increased, for example, by fidgeting.