How do environmental mismatches contribute to obesity?

In Darwinian medicine, obesity is understood as a consequence of an environmental mismatch—a discrepancy between the conditions in which humans evolved and the modern environment they now occupy.1

For the vast majority of human history, our ancestors lived as nomadic hunter-gatherers, a lifestyle that required high levels of physical activity and involved a diet significantly different from modern consumption patterns. Evolutionary history prepared the human body for this active, resource-scarce existence. In contrast, modern environments in many parts of the world provide an abundant supply of inexpensive, processed, high-calorie foods rich in sweeteners and saturated fats, paired with increasingly sedentary living habits.23

Because human physiology has changed very little over time, our bodies are not optimized to handle the constant availability of energy-dense foods combined with low physical exertion. This mismatch leads to a state where caloric intake frequently exceeds caloric expenditure, contributing significantly to the global obesity epidemic.345