Childhood obesity is a major public health challenge across the developed world, and it is vital to understand the modifiable factors that contribute to it. The influence of early-life nutrition on predisposition to later obesity and metabolic disease is now well established. Much research has concentrated on the preventative effects of breastfeeding in relation to childhood obesity risk, but the optimal timing of introducing solid foods has received far less attention. This remains a much-debated and contentious issue, and differing guidelines from international bodies have caused confusion among parents. There is no conclusive evidence from current research that introducing solids before six months of age is associated with an increased risk of obesity in infancy or childhood. Current studies suggest that the most clearly established risk factor for childhood obesity is maternal body mass index. There is a need for continued research in this area.