New Zealand (NZ) and the United States (US) are experiencing an epidemic of obesity in early childhood, with 25-30% of preschool-aged children being overweight or obese. In developed countries where over-nutrition is a much greater threat than famine, we urgently need effective solutions to reduce the associated inequities and health burden associated with overweight. Importantly, across cultures, dietary variety early in life is relatively small as the infant diet is largely milk-based for at least the first 6-7 months. Identifying alternative targets to improve growth trajectories of infants is thus imperative. Maintaining good sleep habits from birth throughout childhood is emerging as a critical factor for health, but interventions need to show that changing sleep behaviours can actually reduce obesity. This proposed NZ-US collaboration combines childhood obesity and sleep research expertise from highly experienced investigators to develop interventions, gain international funding, and contribute to reducing inequities in health.