Old wiring, new environment
The human body developed slowly, across generations. A preference for energy-dense food and a tendency to save effort can be one way to understand how people adapt to their surroundings.
Modern daily life is different in many ways. Food is readily available, and some everyday situations require less movement than before. That can help explain why choices sometimes feel conflicted, without using one biological account as an explanation for everyone.
The environment influences choices, but each person's situation is its own whole.