Obesity and cardiometabolic diseases are leading causes of morbidity and mortality among adults worldwide. These conditions significantly contribute to and exacerbate other major causes of illness and death, including cancer, neurodegenerative diseases, and chronic kidney disease. The growing burden of these diseases has increased the interest of modern medicine in understanding metabolic processes and health, with diet emerging as a pivotal modifiable factor, alongside physical inactivity and smoking. In this review, we discuss the pathophysiological and evolutionary foundations of metabolic processes that may link "unhealthy" nutrition to obesity and cardiometabolic diseases and review the current literature to assess the effects of various diet interventions and patterns on cardiometabolic parameters. Special emphasis is placed on summarizing the latest, albeit partially contradictory, evidence to offer balanced dietary recommendations with the ultimate aim to improve cardiometabolic health.