[Bit#18] From a Badge of Survival to the Root of Disease: The Cruel Paradox of Obesity

1. The Miracle of Fat Storage: Humanity’s Ultimate Survival Strategy

For our ancestors, body fat was not merely excess weight; it was the most powerful insurance policy for staying alive and a key to survival. In the prehistoric era, humans could not resolve their next meal as easily as we do today. During harsh seasons when hunting failed or foraging became impossible, starving for days was a common occurrence. During these times, the fat stored within our bodies functioned as a vital emergency generator.

Why was fat the chosen medium? Our bodies evolved to prefer fat over carbohydrates when storing energy. This is because fat can yield more than twice the energy of carbohydrates for the same weight. For early humans who needed to pack energy as efficiently as possible into a limited space, fat was the optimal choice. The ability to feast as much as possible when food was available and rapidly convert that excess energy into fat was the premier survival skill of the time. Only those with exceptional talent in this area could survive the long tunnels of famine. Ultimately, we are the descendants of these “fat storage experts” who emerged victorious from that fierce competition for survival.

However, this is where the tragedy begins. This brilliant survival strategy, etched into our bodies over millions of years, has begun to clash with the abundant environment of the modern world. Our bodies still tremble at the fear of tomorrow’s hunger, leading to a relentless accumulation of energy. The mechanism of blessing that once saved us has now returned as a blade threatening our health. Human bodies are still lingering in the Paleolithic era, while the world has simply changed too fast.

2. The Legacy of Obesity Genes: Why the Thrifty Gene was Engraved

Our genetic map is deeply etched with a history of hunger. Scientists often explain this through the “Thrifty Gene” hypothesis. In particular, the FTO gene, which has recently gained significant attention, is a representative obesity-linked gene. This gene instructs our metabolism to regulate itself toward storing energy rather than consuming it. In times of scarcity, individuals with this gene held a significant advantage, as they could store more energy even with minimal food intake.

Why then is this once-grateful gene now a source of resentment? The answer is simple: while our genetic blueprint remains unchanged from tens of thousands of years ago, our environment has shifted in the exact opposite direction. The FTO gene acts on the hypothalamus of the brain to drive cravings for high-calorie foods. It triggers the primal instinct of our ancestors who had to eat whenever food was available, even if they were full.

This gene does not just increase appetite; it lowers the basal metabolic rate to minimize the energy consumed even while at rest. It acts as a “miser,” hoarding energy to put into fat cells. Ultimately, possessing an obesity gene is not evidence of laziness, but rather a badge of a resilient survivor who endured history’s most brutal famines. The problem is that in modern society, this gene never gets a break. In a world where high-calorie food is everywhere, the body never lowers its guard, fearing “we might starve at any moment.” The gene is working hard to save its owner, but the irony is that it manifests as obesity and adult diseases in modern humans. Our survival instinct has fallen into the trap of abundance.

3. System Malfunction: Hormonal Resistance in an Age of Plenty

The human body possesses an originally sophisticated energy regulation system. The main characters are hormones that send signals when hungry and tell us, “You can stop eating now,” when we’ve had enough. Among them, “Leptin,” secreted from fat cells, is the key messenger that delivers the feeling of fullness to the brain. However, as obesity progresses, a fatal error occurs in this once-smart system.

Why does this control device malfunction? When there is too much fat in the body, leptin hormone is poured out excessively. The brain listens well at first, but after receiving strong signals for too long, it eventually develops a resistance. This is called “Leptin Resistance.” As the brain begins to ignore the signal of being full, the body continues to mistakenly believe it is hungry even when fat is overflowing. it is like a whisper not being heard in a room filled with noise.

Here, another protagonist, Insulin, enters the scene. When we consume excessive sugar or refined carbohydrates, insulin levels spike. Insulin acts as a gatekeeper that stores energy as fat, and when this level stays high, our bodies completely lose the opportunity to burn fat. A worst-case pincer attack begins where leptin fails to make us forget hunger, and insulin tightly locks the door to the fat warehouse. Ultimately, obesity is not simply a problem of lacking willpower; it is closer to a collapse of our body’s chemical communication network. As cells fail to read each other’s signals and malfunction, the body craves energy, perceiving itself to be in a state of starvation despite the abundance. The sophisticated hormonal system that saved humanity is now drifting aimlessly in front of the excess nutrients of the modern era.

4. The Evolutionary Paradox: How to Solve Hunger Amidst Abundance

We sit at 21st-century dinner tables with Paleolithic genes. Evolutionary speed moves slowly over tens of thousands of years, yet our food environment has undergone a cataclysmic change in just a few decades. If we cannot change our genes immediately, we must devise a clever strategy to trick this broken survival instinct.

The first thing we must do is gift our bodies with a “pseudo-famine.” Just as humans did in the past, we must intentionally create periods of not eating to induce the body to use stored fat. In modern science, this is called intermittent fasting. We must break the habit of keeping insulin levels high by constantly snacking and instead allow the body time to open the doors of the fat warehouse. Only then can the tightly locked fat-burning system be reactivated.

Furthermore, we must escape from the “fake energy” of processed sugar and refined carbohydrates. These intensely stimulate our brain’s reward system and cause the obesity gene to run rampant. Instead, we should create an environment where hormones can find their voice through a natural diet rich in fiber. Fiber slows down digestion, preventing a rapid rise in insulin and giving the brain time to recognize satiety. Obesity is not just a state of being overweight, but a scream from a body struggling to adapt to the times. It is time to soothe that desperate survival instinct that once saved us with rational control. Understanding the instincts of our genes and redesigning our environment is the only way to turn the “legacy of blessing” we inherited back into a “healthy future.”