Currently the world is facing an incredibly costly epidemic of obesity. Almost two-thirds of UK adults are either overweight or obese with estimated financial costs to the UK economy alone of £27 billion per year. While fundamentally obesity is a disorder of energy balance, several decades of research has demonstrated that maintaining energy balance is much more complex than the ‘energy in equals energy out’ equation that was once touted. The purpose of the 2018 Nutrition Society Summer Conference, ‘Getting energy balance right’ was to provide insight into the numerous factors influencing energy balance, considering varying needs across the lifespan, while highlighting advances and gaps in knowledge. Papers presented in this issue illustrate the wide range of factors involved in maintaining energy balance, including: epigenetics, the gut microbiome, physical activity and dietary factors including sugar. Given the complexity of energy balance, systems approaches were highlighted as useful for both understanding metabolism and pathophysiology, and for understanding how public health interventions to treat and prevent obesity should be implemented. The meeting concluded that numerous stakeholders, from individuals, to schools, industry and government, have roles to play in fostering a positive food environment that facilitates the maintenance of energy balance throughout the lifespan.