Early life factors that affect obesity and the need for complex solutions.

The prevalence of obesity increases with age but is apparent even in early life. Early childhood is a critical period for development that is known to influence future health. Even so, the focus on obesity in this phase, and the factors that affect the development of obesity, has only emerged over the past two decades. Furthermore, there is a paucity of iterative work in this area that would move the field forward. Obesity is a complex condition involving the interplay of multiple influences at different levels: the individual and biological level, the sociocultural level, and the environmental and system levels. This Review provides a brief overview of the evidence for these factors with a focus on aspects specific to early life. By spotlighting the complex web of interactions between the broad range of influences, both causal and risk markers, we highlight the complex nature of the condition. Much work in the early life field remains observational and many of the intervention studies are limited by a focus on single influences and a disjointed approach to solutions. Yet the complexity of obesity necessitates coordinated multi-focused solutions and joined-up action across the first 2,000 days from conception, and beyond.