The conventional narrative of human eating behavior often suggests that we overeat because we are hardwired to crave calories for survival. This view implies that obesity is an inevitable byproduct of evolutionary programming, a relic from our ancestors who needed to store fat for times of scarcity. However, this explanation oversimplifies the complexities of human behavior, psychology, and the modern environment.

As Mark Schatzker argues in The End of Craving, while humans require calories to survive, our biological programming doesn’t inherently drive us to overconsume them. Instead, the environmental disruptions of the modern world manipulate our behaviors, reshape our psychology, and lead to the widespread obesity crisis. The interplay between these factors has created a perfect storm, overriding natural regulatory systems and fostering patterns of overconsumption largely disconnected from biological needs.

Human evolution prioritized efficiency over excess. Early humans lived in environments where food was scarce, and physical activity was constant. While carrying extra fat may have been advantageous during periods of famine, it also came with significant drawbacks. As Schatzker highlights, a greater body mass reduced agility, increased the risk of injury, and made individuals more vulnerable to predators. Excessive weight also hindered the ability to chase and capture prey, diminishing survival odds.

Traits that favored energy balance—efficient use of calories rather than unchecked consumption—were far more advantageous. To support this balance, humans evolved intricate systems of energy regulation, including hunger and satiety signaling, which were fine-tuned for natural food environments. These systems worked well in environments where foods were whole and minimally processed. But today, hyper-engineered food landscapes exploit these systems, disrupting the balance that evolution worked so meticulously to create.

Dana Small, a leading expert in neuropsychology and nutrition science, has shed light on how modern food environments distort our biology. Her research on "nutritive mismatch" reveals how ultra-processed foods hijack the body’s natural regulatory systems. In her groundbreaking experiments, Small demonstrated that when sweetness—a cue for incoming calories—does not align with actual caloric content, metabolic processes falter.

Small created a series of solutions with varying calorie amounts, all designed to taste equivalently sweet, mimicking the caloric content of 75 calories of sugar. Remarkably, only the solution where sweetness matched caloric content triggered the body’s expected metabolic response, efficiently burning the calories. Mismatched solutions—where sweetness falsely signaled caloric content—showed no such response. This disruption, which Small terms “nutritive mismatch,” illustrates how processed foods confuse the body, leaving it unable to metabolize calories effectively. In natural food environments, sweetness reliably indicated energy, and the body responded accordingly. Today, these mismatched cues foster cycles of overconsumption, as the body perpetually chases an equilibrium it can no longer find.

Small’s findings challenge the assumption that overeating is a natural behavior. Instead, they reveal that the modern food environment manipulates our biological systems, encouraging patterns of eating disconnected from genuine physiological needs. This disruption is compounded by the psychological dynamics of craving, a distinction Schatzker emphasizes in his work.

Hunger is a biological drive designed to meet energy needs, while craving is a psychological state driven by the brain’s reward system. Cravings are fueled by dopamine, the neurotransmitter associated with anticipation and reward. In the context of food, dopamine surges in response to cues like the sight or smell of hyper-palatable options, triggering an intense desire to eat. Yet, these foods often fail to deliver the satisfaction the body expects, creating a disconnect between “wanting” and “liking.” This cycle mirrors addiction, where the relentless pursuit of reward becomes disconnected from actual satisfaction.

Repeated dopamine surges condition the brain to seek out ultra-processed foods—not because they nourish, but because they promise a fleeting reward. Over time, this psychological shift transforms eating into a pursuit of gratification rather than a response to hunger. The modern food environment, with its hyper-palatable, mismatched offerings, capitalizes on this vulnerability, driving a feedback loop of overconsumption and dissatisfaction.

The obesity crisis, then, cannot be reduced to an evolutionary imperative to overconsume calories. It is the product of environmental disruptions that exploit human biology and psychology, distorting natural regulatory systems. Small’s research on nutritive mismatch and Schatzker’s insights into craving illuminate the profound impact of these factors, offering a more nuanced understanding of why we overeat in the modern world.