Shifting processes model: a conceptual model for sustainable weight management.

Weight-loss maintenance is widely accepted to be a difficult and often elusive process. The transtheoretical model (TTM) provides a useful description of five stages of change. Applied to weight management, weight loss occurs during the action stage and weight-loss maintenance occurs during the maintenance stage. Despite its broad utility, the TTM does not adequately explain the complexity involved with a shift from action to maintenance. Based on Engel's (G. L. Engel, 1977, The need for a new medical model: A challenge for biomedicine, Science, Vol. 196, pp. 129-136) biopsychosocial model and family systems theory, a shifting processes model is proposed to describe the potential differences and shift that occurs between weight loss and weight-loss maintenance processes within relational contexts.