Why We Get Fat: And What to Do About It

Book Review: 3/5 Impact On Me (Book By Gary Taubes)

Read more about the book here

The author's story begins by showing that obesity existed in New York long before high fructose corn syrup, McDonald's, or KFC—even during the Great Depression.

He challenges the common belief that obesity happens simply because of “calories in, calories out.” This idea is popular but incorrect.

Instead, he suggests that we define obesity as a condition in which the body stores excessive fat. It’s about fat regulation, not just calorie surplus—similar to how hormones affect growth in children. When kids eat extra, they grow taller, not fatter. This points to the role of growth hormones. So, what hormones cause adults to store fat? That’s the real question.

He shares the example of poor versus rich people in Manhattan. Poorer residents were more likely to be obese. Another example was Native American reservations—many people became obese when they started eating modern foods like bread, coffee, and white flour. This happened regardless of how much they exercised.

He highlights a strange combination—people can be both obese and malnourished. Some communities eat fewer calories than the WHO recommendation but are still obese. In some families, mothers are overweight while their children are malnourished.

Medical guides often recommend calorie restriction for diabetes and weight loss. But even those guides admit that this doesn’t work long-term. They also suggest more than 60 minutes of exercise a day to prevent weight gain. Why 60? Because less than that didn’t show results, and they hoped more might help—but they didn’t have proof that 60 minutes was sufficient either.

Exercise revenues have grown in the U.S., but obesity rates haven’t dropped. Some studies found that aerobic exercise didn’t result in weight loss. Strength training also didn’t prove effective because it’s hard to show that muscle burns fat consistently.

When people exercise, they usually feel hungrier and eat more. Most researchers ignore this effect. Even one extra bite of bread a day adds up to about 20 calories. That small number, if eaten daily, could lead to major weight gain over a lifetime.

But if that were true, then people who maintain a steady weight would have to eat exactly the same amount every day, never even a bite off. That’s not realistic.

He shares studies about identical twins who have similar body types—how could two separate people eat exactly the same every day? Or examples of different cow breeds—some are naturally muscular, others naturally fat—even though both are bred for meat.

People often misinterpret thermodynamics when they talk about weight gain. It’s not just “eat more, gain more.” It’s more accurate to say that if your body stores more energy, then your weight goes up.

In HIV treatment studies, people gained a lot of weight suddenly after treatment began. It wasn’t about food—it was about how their body changed due to hormones and medications.

Estrogen affects how your fat cells behave. When your body lacks estrogen, your fat cells make more of a fat-storing enzyme called LPL (lipoprotein lipase). This enzyme pulls fat from your bloodstream into your fat cells, reducing the energy available for your body and making you feel hungrier.

Teenagers eat more when they’re growing taller. We say growth causes more eating. But when people gain fat, we say it’s because they overeat. That logic doesn’t line up. Is it eat → growth, or growth → eat?

In animal studies, some animals became obese even when fed a restricted diet. They lost muscle and shrank organs just to hold onto fat. That shows a regulation problem, not a calorie problem.

The body stores fat as triglycerides and uses it as fatty acids. Even if you overeat or undereat, fat can be released into the bloodstream and reabsorbed later. It’s a cycle.

Testosterone lowers LPL in fat cells. So, when men age and testosterone drops, their belly fat cells make more LPL. That leads to more belly fat.

In women, LPL activity is higher in the hips and thighs, especially during pregnancy. After childbirth, the fat-regulating enzyme shifts to the breasts for milk production.

Another enzyme, HSL (hormone-sensitive lipase), tells fat cells to release fat. Insulin works against this—it increases LPL and tells muscles to use carbs first instead of fat. So, more insulin means more fat storage.

That’s why the author recommends eating low-glycemic carbs. Foods that spike blood sugar also spike insulin, which leads to more fat storage. High-GI foods are also cheaper, which makes them more common.

Fructose, in particular, is harmful. While glucose spikes blood sugar, fructose is more likely to turn into fat. It’s not just about empty calories—fructose itself harms your body.

Your insulin levels rise even when you think about food. That’s how your body prepares. But during that time, your body also blocks fat use. When you finally eat, the food feels especially satisfying because of that built-up insulin.

That’s why the first bite of food tastes better than the last.

Insulin also tells your kidneys to hold on to sodium. When you cut carbs and insulin drops, your body releases sodium and water—so you lose water weight.

Modern fruits are also much sweeter than they used to be. They’ve been selectively bred to be calorie-dense and sugar-rich. This helped me decide to reduce my (possible) overeating of fruits.

The author strongly advises avoiding white flour and sugar.

When you first stop eating carbs, you might feel dizzy. But that passes. It’s like quitting smoking—it feels bad at first, but your body adjusts.

Doctors recommend different low-carb diets. Some allow 120 or 60 grams of carbs a day—just enough for brain function (although that’s debated). Others allow one pasta dish or dessert per week. Some go for zero carbs altogether.

I rate the book 3 out of 5. I’ve read this author’s earlier book and a few others on this topic, so most of the ideas weren’t new to me.

What stood out were the studies that clearly disproved popular beliefs. That gave me more confidence to explain these ideas to others. I now understand better how to argue that saturated fat, total calorie count, or lack of exercise isn’t the root problem.

The book helped me strengthen my understanding of how fat regulation works and why focusing only on calories or gym time won’t solve obesity.