Obesity has been a global health problem since the twentieth century. Despite the intensive research, there is no scientific consensus on the onset of obesity. The energy balance model (EBM) and the carbohydrate-insulin model (CIM) are two competing obesity theories, each with supporting and conflicting evidence. In this essay, I propose a new model, the energy-rush and insulin model (ERIM) which integrates not only the energy intake and expenditure, but also the food composition and digestibility, to explain how the high energy-rush and insulin secretion contribute to the development of obesity. The ERIM offers a novel framework to explain how obesity occurs and proposes new recommendations which may reverse the obesity epidemic in the future.