The Case for Keto: Rethinking Weight Control and the Science and Practice of Low-Carb/High-Fat Eating

by Gary Taubes

If the goal is to burn fat without hunger, then nutritional ketosis is a good thing.

First, we all respond to carbohydrates differently. Enormous variation exists from person to person. That’s one very good reason why, given the same foods to eat, some of us will grow up to be built like fashion models and some of us will be extremely obese. Moreover, different cells and tissues even in the same individual respond differently to insulin. Here, too, there’s enormous variation. When tissues and cells become resistant to insulin, they do so at different rates and different levels of insulin in the circulation.

Elevating insulin even slightly above some hypothetical threshold will cause fat cells to enter storage mode. The longer the insulin remains elevated, even if by barely measurable amounts, the longer fat cells will be storing fat, not mobilizing it. For this reason, some of the most prominent diabetes researchers in the world—i.e., the specialists whose purview included paying attention to insulin—had speculated in the 1960s and ’70s that having too much insulin circulating in the blood or having fat tissue excessively sensitive to insulin might be the cause of obesity. It might be the reason, as Bruch said, the metabolism shifts too much into storage mode, the reason some of us may trap five or ten or twenty or even one hundred excess calories a day as fat into our fat tissue and others don’t. These researchers were just speculating on what seemed like an obvious cause-and-effect possibility, a prime suspect in the mechanism of why we get fat.

colleagues wrote in their technical language, insulin inhibits “lipolysis,” the breakdown and release of fat from the fat cells and use of fat for fuel.

But then there’s the threshold (what the arrows I added are pointing to in the figure). When insulin gets sufficiently low, when the negative stimulus of insulin is sufficiently draconian, everything changes. It’s like a switch is thrown. Above the threshold, fat cells hold on to fat. Below it, they release their stored fat into the circulation, and the other cells in the body take it up and use it for fuel.

While all of us, lean or fat, must have critical carbohydrate thresholds, the more predisposed we are to put on fat, the easier we fatten, the lower the insulin threshold is likely to be or the less time, at least, we spend below it.

This may be true for many people and maybe even most. It’s probably the reason many people seem to achieve and maintain a healthy weight merely by making sure their carbohydrates are fiber-rich—slow to digest and absorb. This keeps insulin relatively low

Authorities like to say that glucose—blood sugar—is your brain’s preferred fuel, but that, again, is because your brain burns glucose for fuel when you’re eating a carb-rich diet. It’s conceivable that our bodies decided, figuratively speaking, that since our brains use up so much of the energy we generate—around 20 percent—having our brains burn glucose would be necessary to control blood sugar in a high-carb world, even if ketones were somehow a better source, like a higher-octane fuel for your car.

When insulin is below the threshold, when the switch is in the off position, your body is burning the fat you’ve stored. It will continue to burn fat as long as you remain below the threshold.

Above the insulin threshold, you have to replenish frequently. You have a limited supply of carbohydrates, and insulin works to keep the carbohydrates you’ve stored (a maximum of about two thousand calories of glycogen) locked away as well. As your blood sugar drops, you’ll get hungry. And because carbohydrates are your fuel above the threshold, you’ll hunger for carbohydrate-rich foods.

You’d think more calories would mean less hunger, but it would cause more.

When you cut out carbohydrates, you lower insulin sufficiently, mobilize and burn fat,

and lose weight. Because you burn your own fat for fuel, your body remains well fed, and you feel no hunger.

You’re not losing fat because you’re eating less. You’re eating less, and are content with eating less, because you’re losing fat and using that fat to fuel your body.

Physicians who prescribe LCHF/ketogenic eating and who eat that way themselves say it can take days

for this hunger for carbohydrates, the urge to continue cheating, to disappear. This is the slippery slope.

(Of course, if the lean friend enters the bakery and eats a cinnamon bun as well, no one judges him for it, because, well, he’s lean. “Before I got on the plane,” as Roxane Gay writes in Hunger, “my best friend offered me a bag of potato chips to eat, but I denied myself that. I told her, ‘People like me don’t get to eat food like that in public,’ and it was one of the truest things I’ve ever said.”)

Replacing carbohydrates with fat serves multiple purposes. It keeps calories high and insulin low, which means the body is not semistarving and doesn’t respond physiologically as if it were.

We can think of them as variations on a theme or on a spectrum of carbohydrate restriction, all of which works to lower insulin.

Fasting, defined as the voluntary withholding of foods for days or even weeks at a time—intermittent fasting (shorter time periods) and what is now called time-restricted eating (eating all meals in a short six- or seven-hour

window of the day)—will extend the duration of time we spend under the insulin threshold, mobilizing fat and burning it for fuel.

that’s true, then the physical activity had to increase the length of time their insulin levels stayed under the threshold for mobilizing fat.

aerobic exercise will improve insulin sensitivity because the exercise depletes glycogen stores in the muscles, and the cells then essentially work to fill them back up again.

Someone asked me the other day how I was losing weight. I told them I eat less than 20g of carbs a day. They proceeded to freak the heck out. Told me how dangerous it was. (No.) Asked me if my doc knew. (Yes.) Told me that carbs were essential to human survival….Finally I was like, dude, do you really believe I was healthier 90 pounds heavier than I am now? I really think he wanted to say yes but was worried that I was going to punch his lights out. He probably would’ve been right. —RACHELLE PLOETZ, on her Instagram account #eatbaconloseweight

An almost universal misconception about nutrition and modern medicine—one shared by authority figures, physicians, and the journalists who cover the field—involves when clinical trials are necessary to guide our decisions and when they’re not. You do not need a clinical trial (costing tens of millions of dollars with tens of thousands of subjects) to tell you whether LCHF/ketogenic eating, or any regimen from vegan to carnivore, will allow you to achieve significant weight loss easily, without hunger, and make you feel healthier than you did. You can try any of these diets yourself and find out.

To believe that it applies to all of us, you have to believe that

those of us who fatten easily, as I’ve discussed and disagreed with strongly, are no different from those lean folks physiologically and hormonally.

As one of these researchers pointed out to me when I interviewed him, the added time is not in the prime of our lives but rather at the very end of our lives. This seems obvious, but it’s a point worth pondering. Instead of dying, say, in March of our seventy-fifth year, we die in April or May. A ninety-year-old is likely to get a few more months being ninety or maybe will

Marshall Becker, a professor of public health at the University of Michigan, suggested that avoiding fat or saturated fat to prevent heart disease is “analogous to stewards rearranging the deck chairs on the Titanic.”

Physicians who now prescribe these diets commonly say that they rarely if ever prescribe drugs to their patients for blood sugar control or hypertension; rather, they de-prescribe, they get patients off medications. That’s compelling testimony.

Always Hungry?: Conquer Cravings, Retrain Your Fat Cells, and Lose Weight Permanently by David Ludwig, a physician and professor of nutrition at Harvard, and to study its low-carb recipes. “One thing I love about the low-carb, high-fat diet, which I say again and again to my patients, is it makes you feel better.”

Nobel laureate Louis Alvarez called it “intellectual phase lock.” People believe something because people they respect believe it, and if they’re doing research, they report what they’re supposed to find, and they see what they expect to see, whether it’s really there or not.

Eating mostly plants, in other words, just seems right to those who recommend it to us.

As for blood pressure, insulin induces your kidneys to hold on to sodium. (Salt is sodium chloride, and the sodium is the player here.) This is one of the many things insulin does.

Now blood pressure will increase as your body retains water to keep the sodium concentration in your circulation constant.

but the only way we can get some reliable information is by adding them to our diets or taking them away and seeing what happens. Do we get leaner? Do we get healthier? Do we feel better or worse?

If those of us who are predisposed to be insulin resistant, obese, and/or diabetic in the modern food environment get fat or stay fat eating beans, legumes, and grains, we have a conflict that must be resolved.

achievement focused on the subtle ways these approaches differ rather than what they all have in common: the advice to avoid or mostly avoid, at the very least, refined grains and sugars.

In every case, he wrote, the foods they craved were breads and starches and desserts. As a consequence, Brillat-Savarin considered it indisputable that grains and starches were the principal cause of obesity*2—along with a genetic or biological predisposition to fatten easily, which not everybody has—and that sugar exacerbated the fattening process. He lived in a time, though, when sugar was still a luxury for the wealthy, and sugary beverages were exceedingly hard to come by, at least compared to their ubiquity a century later. So he focused his advice on starches and flour, assuming that abstinence from flour would imply abstinence from sugar, since sugars back then came predominantly in baked goods, pastries, and desserts.

He, too, had struggled for decades with his weight before being convinced, in his case, by a London physician, to avoid sugars, starches, and grains, and thereafter he effortlessly slimmed down.

Like any device tasked to do a job it isn’t designed to do, the liver does a poor job of metabolizing this daily flood of fructose. Liver cells use as much of the fructose as they can to generate energy, but they convert the rest, the excess, to fat. Reasonably reliable research suggests that this fat is trapped in liver cells, leading to a condition known as nonalcoholic fatty liver disease, which is associated with obesity and diabetes and is also becoming an epidemic in the modern world. Some very good biochemists think that the backup of fat in these liver cells, whether temporary or chronic, is a likely initial cause of the insulin resistance we’ve been talking about and that we’re trying to prevent and/or reverse. In short, insulin resistance starts in the liver and then becomes systemic.

the fat in the liver tends to go away. This suggests that insulin resistance—in children, at least—would resolve along with it.

The glucose raises blood sugar and stimulates insulin secretion, the fructose overwhelms the liver and causes fatty liver and insulin resistance, so that we secrete ever more insulin to all those other carbohydrates.

For many of us, we will have to minimize our insulin secretion to create and prolong that negative stimulus of insulin deficiency,

A sugary treat may not be any less seductive than it ever was. Sugar may always have the power to excite our taste buds (and our liver) and trigger cravings for more. But the key is to not succumb. As our bodies switch to burning fat for fuel, the ability to say no to sugary treats will be reinforced. Many foods with sugar in them will taste too sweet as our tastes change. This is commonly reported. We will also become more adept at and habituated to keeping our lives and our environments sufficiently sugar-free

rare patient can be a moderator when it comes to tasty carbs and succeed. Most of us need to be abstainers. Like people with alcoholism, drug addiction, and smoking, we need to avoid completely, and then we’ll have better odds of success.

The only way to eat a satiating meal while minimizing insulin secretion is to add fat. It’s the one macronutrient that does not stimulate an insulin response.

When cooking vegetables, do so with copious butter or olive oil, then eat them with olive oil or melted butter. Lunch can be a salad so long as the salad dressing has plenty of fat and is low in carbs. Put olives or avocado on the salad or perhaps hemp seeds.

By using vegetables as a conduit for fats, LCHF/ketogenic eating can be mostly plants if not all plant foods. It may be harder to do without the fatty animal products, but it’s certainly doable.

If you were ordering this in a restaurant, you would order the roast chicken and ask the waiter or waitress to replace the potatoes with more broccoli or a green salad. Simple enough.