Lifestyle is a complex and often generic concept that has been used and defined in different ways in scientific research. Currently, there is no single definition of lifestyle, and various fields of knowledge have developed theories and research variables that are also distant from each other. This paper is a narrative review of the literature and an analysis of the concept of lifestyle and its relationship to health. This contribution aims to shed light on the lifestyle construct in health psychology. In particular, the first part of this manuscript reexamines the main definitions of lifestyle in the psychological and sociological fields through three perspectives: internal, external, and temporal. The main components that characterise lifestyle are highlighted. The second part of this paper explores the main concepts of lifestyle in health, underlining their strengths and weaknesses, and proposes an alternative definition of a healthy lifestyle, which integrates the individual dimensions with the social and cycle dimensions of life. In conclusion, a brief indication of a research agenda is presented.