In this chapter, we will provide an overview of the role of nutrition in health and disease. We will present the principles of metabolism and the impact of macro- and micronutrients, discussing the roles of nutritional supplements and nutraceuticals. Over the past 50 years, a significant lifestyle change has occurred globally, characterized by the consumption of energy-rich, highly processed foods paired with reduced physical activity. We will provide evidence that diet is a key environmental factor in the pathogenesis and progression of many metabolic diseases, such as obesity, T2D, and CVD.