The body is not broken

For nearly all of human history, the threat to survival was scarcity rather than abundance: the winter that ran long, the hunt that failed, the illness that arrived when stores were already low. The systems that regulate hunger, fat storage and energy expenditure were shaped by that world, and they are remarkably effective at protecting stored energy when it begins to disappear.C-I-01

In evolutionary terms, that effectiveness is the reason the design survived rather than a flaw that appeared recently. Every one of your ancestors, without exception, lived through scarcity with enough reserve to reproduce, which means you are descended entirely from people whose bodies were good at holding on to energy.

In practical terms, when your body resists weight loss, it is not malfunctioning. It is doing the one thing it was most strongly selected to do.

The mismatch is one of speed. Genetic change in humans moves through generations, while the food environment, the light environment, the activity environment and the microbial environment have all changed within a handful of them.

Researchers who study why non-communicable disease became common describe this gap directly. Conditions that were rare throughout human history are now ordinary, and the framework that best explains the change is a mismatch between evolved physiology and the environment in which it now operates.C-I-02

It is worth noting that this is a literal claim rather than a metaphor. It concerns two rates of change, one biological and slow, the other environmental and fast, and what happens in the gap between them.

The gut microbiome of people living in non-industrialized settings is measurably more diverse than that of people in industrialized ones, and deep sequencing of hunter-gatherer populations has recovered microbes that appear to have largely vanished from industrialized guts.C-I-03 Whatever those organisms were doing, most people reading this no longer carry them.

The microbiome is one system among several. Food now requires no preparation and delivers energy faster than satiety signaling was built to register, light no longer tracks the sun, and movement has been engineered out of daily life rather than given up by choice. None of these is a moral failure; they are simply the conditions, and the conditions changed faster than anything inside you could.

Many people assume that weight must be either genetic, and therefore fixed, or behavioral, and therefore their own fault. In reality, the evidence supports neither position.

The key detail is the gap between those two numbers.C-I-04 Susceptibility is inherited and real, but it cannot be reduced to a set of genes that anyone can currently point to, and it does not express itself the same way in every environment.