Why We Get Fat

Why is it that so many of us try to eat less, move more, and yet remain overweight—or even gain more fat? Gary Taubes’s Why We Get Fat: And What to Do About It addresses this pervasive question with meticulous scientific reasoning and historical insight. He argues that obesity is not caused by overeating or laziness, as we’ve long been taught, but by a biological malfunction driven by hormones—mainly insulin—and triggered by the carbohydrates we eat.

Taubes dismantles the conventional wisdom of “calories-in, calories-out,” replacing it with a hormonal view of fat accumulation. We don’t get fat because we indulge ourselves; we get fat because certain foods—especially refined carbohydrates and sugars—disrupt our body’s internal regulatory system. In his telling, obesity is a disorder of fat storage rather than of energy balance. The difference is profound: it shifts blame from willpower to metabolism, from morality to biology.

The Collapse of the Calorie Paradigm

For more than half a century, public health authorities have claimed that excess weight results when we consume more calories than we expend. The cure, they told us, was simple: eat less, move more. But Taubes, echoing earlier scientists such as Hilde Bruch and Gustav von Bergmann, shows this model to be inadequate. If all it took was a small adjustment—hundreds fewer calories burned or eaten—why do millions struggle despite decades of dieting?

Taubes uses examples from historical studies on obesity, like Dr. Bruch’s 1930s case studies of obese children who were physically incapable of losing weight through eating less. He highlights paradoxes such as the obesity epidemic among the poor or among early twentieth-century Native American tribes, who were not consuming excess calories but were living on cheap refined flour and sugar. These contradictions, he argues, reveal that overeating and inactivity are symptoms—not causes—of fat accumulation.

Biology, Not Physics

Taubes contends that obesity must be understood through biology—through the hormones and enzymes that regulate fat storage—not through physics or thermodynamics. While the laws of energy conservation are universal, they don’t tell us why fat accumulates in the body. They merely describe what happens when it does. He compares the logic of calories-in/calories-out to explaining why a room gets crowded by saying more people entered than left—it’s true but meaningless.

Instead, Taubes directs our attention to insulin, the hormone that determines whether calories are burned or stored. When insulin levels rise—especially after consuming carbohydrates—fat cells lock away energy and prevent its release. When insulin levels fall, those fat stores are released and burned. This simple principle overturns decades of advice about “balanced diets” and “fat-free living.”

The Promise and Peril of Carbohydrates

From bread to soda, from potatoes to fruit juice, Taubes identifies carbohydrates as the driving force behind insulin secretion. “Carbohydrate drives insulin drives fat,” as Harvard’s George Cahill once summarized the science. Taubes reintroduces this forgotten truth, showing that when insulin is chronically elevated, we accumulate fat continuously—even at normal caloric intake. This helps explain why obesity rates have soared during an era of low-fat dietary recommendations: we replaced fats with refined carbs and sugars.

Why It Matters

Taubes’s argument is more than nutritional correction—it’s a moral rehabilitation of the overweight. He demonstrates that fatness is not a failure of character but a failure of public health theory. Understanding why we get fat means freeing ourselves from shame and focusing instead on biochemical triggers. His solution is straightforward and ancient: return to the dietary wisdom known before the 1960s—avoid carbohydrate-rich foods, eat real food, and let biology heal itself.

Throughout Why We Get Fat, Taubes sets out to rewire your understanding of dieting. You’ll learn why exercise rarely produces lasting weight loss, why fat storage is hormonally regulated, and how specific foods distort that regulation. Finally, he provides a new framework for eating: one that controls insulin, liberates your fat cells, and redefines what healthy truly means. By the end, you’ll not only grasp why we get fat—but you’ll know what to do about it.

Taubes begins by exposing how deeply engrained and misleading our calorie-based understanding of fatness has become. The concept that we get fat because we eat more and move less feels intuitively true—it’s simple, measurable, and moral. Yet it fails at every level of real-world observation. Evidence from the early twentieth century, including Hilde Bruch’s clinical experience with obese children, already showed that attempts to “eat less” or “exercise more” rarely produced sustained results. These children starved themselves, suffered misery, and yet their fat refused to melt away.

Historical Contradictions

He traces the origins of this mistaken logic through the 1930s and 1940s, when German researchers argued that obesity was not a problem of energy balance but of fat-cell regulation. The real puzzle was why certain populations—even impoverished ones—became obese. Taubes resurrects forgotten examples: the Pima Indians of Arizona, who grew obese and diabetic after shifting from native foods to government rations of flour and sugar; and impoverished Sioux Indians, living on bread and coffee yet paradoxically overweight. Across continents—from Naples to Jamaica—the same pattern emerged: people became fat while eating little.

These cases contradict every calorie-based theory. Poverty should prevent overeating, yet obesity thrives among the poor. Exhausting physical labor should burn calories, yet factory workers and manual laborers in Chile or Mexico suffered high obesity rates. The common denominator was not abundance of food or idleness—it was the arrival of cheap refined carbohydrates.

Exercise and Diet Myths

Taubes extends this argument to the modern fixation on exercise. He argues that “eat less, move more” is not only simplistic—it’s paradoxical. We eat less and move more when we are trying to lose weight, but those behaviors also stimulate hunger. Physical exertion increases appetite; eating less slows metabolism. Exercise physiologists who spent decades running miles still gained weight as they aged, proving the futility of calorie arithmetic. Jean Mayer at Harvard popularized the myth that sedentary living causes obesity, but as Taubes shows, strenuous physical activity often makes animals—and people—eat more, not less.

Why the Authorities Persist

Despite the failure of dietary therapy over half a century, leading health organizations—from the World Health Organization to the American Heart Association—still define obesity as “an energy imbalance.” Taubes explains this persistence as scientific inertia: once researchers moralized obesity as gluttony and sloth, every failed diet became proof of the obese person’s weakness, not of the theory’s flaws. This moral bias transformed obesity from a hormonal disorder to a “behavioral problem.” Psychologists treated patients as addicts. Calories became an article of faith, immune to evidence.

Ultimately, Taubes persuades you to see obesity not as a moral failing but as a medical scandal. For decades, an entire field of nutrition ignored its own data and blamed patients for its mistakes. The takeaway is stark: conventional wisdom hasn’t just failed—it has misled millions into starvation, shame, and chronic illness.

Imagine your fat cells as tiny wallets—storing energy when instructed by hormones and releasing it when permitted. The hormone that controls this process is insulin, and according to Gary Taubes, understanding insulin is the key to understanding fat. When insulin levels rise, whether from eating bread or soda, your fat cells are commanded to store energy rather than burn it. When insulin falls, stored fat is released. For most people today, insulin never truly falls, trapping calories in fat tissue and leaving the rest of the body hungry.

How Insulin Works

Every meal triggers insulin release from the pancreas. Insulin’s immediate purpose is to regulate blood sugar—it tells cells to absorb glucose from the bloodstream. But insulin also affects fat directly: it stimulates an enzyme called lipoprotein lipase (LPL) that pulls fat into tissues, especially fat cells. It simultaneously suppresses another enzyme, hormone-sensitive lipase (HSL), which would normally release fat for energy. This combination guarantees fat accumulation whenever insulin levels are high. Thus, carbohydrates—especially refined ones—create the perfect storm: high glucose, high insulin, and locked-in fat.

The Cycle of Hunger and Storage

When fat is locked away in cells, your muscles and organs run short of fuel. That shortage manifests as hunger. You eat again, insulin stays high, and the cycle perpetuates. Taubes calls this “hidden semi-starvation”—the paradox that obese people may be starving at the cellular level because they cannot access their own fat stores. Over time, fat accumulates while energy levels plummet. This mechanism explains why obesity rarely responds to calorie restriction: you can eat less, but as long as insulin remains high, fat will stay locked away.

Insulin Resistance and Fat Storage

The situation worsens when cells become resistant to insulin. The body compensates by secreting more, raising insulin levels further. Muscles resist insulin first, reducing glucose uptake and energy use; fat cells remain sensitive longer, continuing to stockpile fat. This imbalance shifts how fuel is partitioned: calories that would have powered activity are now stored as fat. The result is fatigue, sedentary behavior, and eventual obesity. Taubes calls this “biology, not behavior.”

In short, insulin acts as the switch determining whether you store or burn fuel. Keeping insulin low—by restricting carbohydrates—unlocks fat cells and restores metabolic balance. This insight reframes obesity from moral failure to hormonal dysregulation and gives you a clear, actionable target: regulate insulin, and you regulate fat.

Taubes’s core prescription is deceptively simple: eliminate carbohydrate-rich foods to lower insulin and let the body burn fat naturally. He distinguishes between types of carbohydrates—some benign, others harmful—and traces how modern diets became saturated with the worst kinds. Until the mid-twentieth century, bread, pasta, and potatoes were known to be fattening. After the 1960s, nutritionists reversed course, labeling fat the enemy and carbohydrates “heart-healthy.” The result was an epidemic of obesity and diabetes.

Good Carbs, Bad Carbs

Carbohydrates vary by how quickly they raise blood sugar—a concept called the glycemic index. Fast-digesting carbs (flour, sugar, soft drinks, potatoes) spike blood sugar and insulin sharply. Slow-digesting carbs (leafy greens, fibrous vegetables) do not. Taubes argues that our modern food supply favors fast carbs: low-cost, densely caloric, and addictive. They flood your blood with glucose, prompt insulin surges, and drive fat storage. When consumed continuously, they trap you in a perpetual state of high insulin and hunger.

The Sugar Effect

Sugar—specifically sucrose and high-fructose corn syrup—is Taubes’s ultimate culprit. He explains the dual nature of sugar chemistry: half glucose, half fructose. The glucose raises insulin; the fructose goes straight to the liver, where it triggers fat production and insulin resistance. This combination leads to fatty liver disease, high triglycerides, and metabolic syndrome. Taubes notes that even populations living in poverty became obese once sugar and flour entered their diets—fertile proof of the biochemical power of carbohydrates to cause fat accumulation independent of wealth or willpower.

Why Low-Carb Works

When carbohydrate intake drops below roughly 50 grams per day, insulin falls, fat cells release stored energy, and metabolism stabilizes. Appetite diminishes naturally because energy becomes accessible again. This effect explains the success of diets like Atkins or ketogenic regimens: they work not by counting calories, but by controlling hormones. “Without carbohydrates,” Taubes writes, “there’s no such thing as essential carbohydrate.” Protein and fat supply all necessary nutrients, while the body’s own fat stores provide steady fuel. Low-carb diets thus reverse obesity’s hormonal cause rather than treating its symptoms.

In essence, Taubes teaches you to see carbohydrates not as a benign energy source but as an endocrine trigger. Every bite of bread or sip of juice affects hormones that decide whether you burn fuel or store it. To lose weight—and keep it off—you must cut off the insulin signal by cutting off its carbohydrate source.

Most people believe that exercise burns fat, but Taubes calls this a pleasant myth. Through decades of research, he shows that increasing physical activity rarely prevents weight gain. In fact, it often leads to eating more. The reason lies in how the body manages energy and appetite. Exercise creates an energy deficit the brain interprets as hunger; thus, you compensate by eating back the calories you burned. Worse, intense workouts trigger fatigue, causing lower non-exercise activity later. Calories-in/calories-out fails because the variables are not independent—change one, and the other adapts.

The Appetite Effect

Taubes cites early twentieth-century obesity specialists like Russell Wilder, who found that bed rest led to faster fat loss than strenuous workouts. Physical exertion increased appetite and slowed fat loss. He also recounts modern examples, such as runners who logged tens of thousands of miles yet gained weight over time. Jean Mayer’s influential claim that sedentary lifestyles caused obesity sounded plausible but was contradicted by data: the poorer laborers who worked hardest were often the fattest. Physical effort promotes hunger, not leanness.

Energy Conservation, Not Burn

The body doesn’t treat exercise as a simple subtraction problem. When you expend energy, other systems compensate by using less. Your metabolism slows, spontaneous movement declines, and fatigue limits total calorie burn. At the hormonal level, chronic high insulin prevents fat release, so the body uses carbohydrates for fuel instead. A person trapped in this metabolic state cannot burn fat efficiently no matter how much they run or sweat. The result: exercise fails to fix what insulin has caused.

Why Exercise Still Matters

Taubes is careful not to dismiss exercise entirely; he acknowledges its psychological and cardiovascular benefits. But he insists that weight control depends on what happens hormonally, not mechanically. Until insulin levels drop, movement merely transfers energy from glycogen stores, not fat tissue. The wise strategy is to first correct hormonal imbalance through diet—especially carbohydrate restriction—and let exercise become a natural consequence of renewed energy. When insulin normalizes, physical activity becomes easier, spontaneous, and sustainable, because your body finally has access to the energy locked in fat cells.

So if you wonder why hours at the gym haven’t slimmed your waistline, Taubes gives a liberating answer: it’s not your fault. You’ve been battling hormones with willpower, and hormones always win.

For half a century, experts have told us to fear fat—especially saturated fat—as the root cause of heart disease. Taubes dismantles this belief systematically. He shows how the low-fat movement emerged from incomplete science and how it coincided with rising rates of obesity, diabetes, and heart disease. The so-called cure became the cause. When we replaced fat with refined carbohydrates and sugars, insulin levels soared, triglycerides climbed, and HDL (“good” cholesterol) fell—all markers of heart risk. The real villain was not butter, but bread.

The Low-Fat Fallacy

Taubes revisits pivotal studies, including the massive U.S. National Heart, Lung, and Blood Institute trials of the 1970s and 1980s, which failed to prove any connection between eating less fat and avoiding heart attacks. The Women’s Health Initiative—nearly fifty thousand participants—found no benefit of low-fat diets for heart disease, stroke, or cancer. Yet authorities persisted, encouraging whole-grain cereal and discouraging steak. The result was higher consumption of carbohydrates and sugar, and worse metabolic health nationwide.

Understanding Metabolic Syndrome

Taubes explains that metabolic syndrome—a cluster of conditions including obesity, high triglycerides, low HDL, high blood pressure, and insulin resistance—is now the dominant cause of chronic disease. It links heart disease, diabetes, and even cancers. All begin with elevated insulin and blood sugar. Carbohydrates increase both; fat does not. Low-fat advice therefore magnified insulin resistance and premature aging. Clinical researchers like Gerald Reaven at Stanford confirmed that reducing carbohydrates—not fat—removes the underlying cause of these disorders.

The Case for Fat

In a surprising twist, Taubes argues that eating fat—even saturated fat—improves heart risk markers. High-fat diets raise HDL, lower triglycerides, and convert harmful small dense LDL particles into benign large ones. In trials like Stanford’s A TO Z study, subjects eating high-fat, low-carb diets lost more weight and improved every cardiovascular measure despite higher fat intake. Fat doesn’t clog arteries; insulin does. The lesson: eliminate fattening carbohydrates and let natural fats fuel your body as they did for our ancestors.

Taubes’s conclusion redefines healthy eating: metabolic health demands controlling insulin, not cutting fat. The foods we’ve feared—meat, eggs, butter—may be exactly what restore balance, while the foods sold as “heart-healthy”—whole grains and sugar-free snacks—are what quietly destroy it.

After dismantling decades of diet dogma, Taubes turns to practical truth: if fattening carbohydrates cause fat, eliminating them is not a “fad” but biological necessity. He urges you to abandon the low-fat paradigm and return to eating in harmony with evolutionary design—meat, fish, eggs, greens, and natural fats. There is no essential carbohydrate requirement; humanity thrived for millennia before agriculture introduced flour and sugar. The only essential nutrients are amino acids from protein and fatty acids from fats. Everything else can be synthesized by the body.

How to Eat

Taubes shares medical guidelines from clinics such as Duke University’s Lifestyle Medicine Center, which prescribe “No Sugar, No Starch” diets. Eat freely of meat, poultry, fish, eggs, and leafy greens. Avoid grains, starches, and sugars. He stresses that hunger naturally diminishes when insulin falls; weight loss happens effortlessly because fat finally becomes accessible for fuel. Unlike calorie restriction, this approach doesn’t demand willpower—it restores normal metabolism.

Controversy and Courage

Though the evidence is strong, many doctors fear departing from official guidelines. Taubes acknowledges that the medical establishment penalizes those who challenge orthodoxy, even when results are life-changing. He encourages readers to think critically and share these ideas with physicians—because true public health reform depends on correcting a century of dogma. His book is not just dietary advice; it’s a manifesto for intellectual honesty and scientific humility.

The Return to Common Sense

Ultimately, Taubes’s philosophy is pragmatic: listen to your body’s biology, not official beliefs. Eat when hungry; stop when satisfied. Focus less on calories and more on the hormonal triggers behind them. By eliminating carbohydrate-rich foods, you free your metabolism to function as intended. This simplicity—eating real food, avoiding sugar and starch—is not radical; it’s human. In doing so, you align with the wisdom of evolution and the insights of forgotten scientists who, long before the calorie era, understood that obesity begins not in behavior but in biochemistry.

Taubes leaves readers with renewed hope and scientific clarity: you can’t fight biology, but you can feed it intelligently. The power to reverse obesity and disease lies not in moral discipline but in metabolic freedom.