What exposures in early life are risk factors for childhood obesity?

Globally, estimates show that 41 million children younger than 5 years of age are affected by overweight and obesity. In many regions of the world, these prevalence rates have increased dramatically, especially in low- and middle-income countries, making childhood obesity a global policy issue. Recent data show that many children are already affected by overweight or obesity by the time they start school; hence, the examination of early exposures, with interventions around these exposures, is warranted. In this review, we outline the main modifiable exposures in early life that can lead to an increased risk of obesity. These exposures can be broadly categorised into parental factors such as obesity and gestational diabetes; dietary exposures in early life, including breastfeeding and complementary feeding and feeding behaviours; physical activity, sedentary behaviours and sleep; and environmental exposures such as maternal exposure to tobacco. We also identify research gaps and opportunities for further research.