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

by Gary Taubes

One powerful implication of these diet books is that obesity is caused not by eating too much but by a hormonal imbalance in the body that eating these carbohydrate-rich foods triggers.

Specific carbohydrate-rich foods create a hormonal milieu in the human body that works to trap calories as fat rather than burn them for fuel.

Some of these physicians had been vegetarians for decades. Some had been vegans. Many are athletes, even ultra-endurance athletes. They prided themselves on eating “healthy” and yet found they had become fatter, diabetic, or prediabetic despite doing everything “right.”

Some of us will just have to abstain from eating carbohydrate-rich foods—specifically, sugars, starchy vegetables, and grains—if we want to be relatively lean and healthy and stay that way.

“To turn what is eaten into fat, to move it and to burn it requires dozens of enzymes and the processes are strongly influenced by a variety of hormones,”

the idea that obesity is a hormonal disorder had effectively vanished from the learned discourse on the subject.

“the intake of foods rich in carbohydrate should be drastically reduced since over-indulgence in such foods is the most common cause of obesity.”

Those who are lean find it easy or at least relatively easy to control their weight. For this reason, they assume the rest of us can also do it.

So if we do get fatter by eating as they advise or if we have the misfortune to stay fat, it must be because we’re not following their wise counsel, or because we just don’t care. Hence the problem is our motivation and our priorities, and we should be ashamed.

Two points here are vitally important. The first is that the nutritional and academic authorities have failed us, and they and we should acknowledge that. Had they not failed us, we would, almost by definition, never have reached this point of epidemic obesity.

Nor is he asking why some people happen to fatten easily and others don’t,

“Probably she [the woman getting fatter as she goes through menopause] does not know or is but dimly aware that the candies she nibbles at the bridge parties which she so enjoys now that she is rested are adding their quota to her girth.” Very scientific, that.

The counterargument, which I’m defending, is Astwood’s belief that those who fatten easily are fundamentally, physiologically and metabolically different from those who don’t. This implies that those of us who fatten easily can get fat on precisely the same food and even the same amount on which lean people stay lean.

The important question, however, is why it is that some of us have to be chronically starved or semistarved—exercise portion control and be hungry for a lifetime—to be lean, or at least leaner, and others don’t.

Perhaps he eats all the time because his body, unlike that of Nicholas and their numerous other lean friends, is singularly dedicated to accumulating fat.

Hunger is a response, not a cause.

Ultimately, these pre–World War II physician researchers were thinking about the problem of excess fat from the perspective of first principles. Rather than asking why fat people eat so much or exercise so little (without even knowing how much of either they do, as is the common state of affairs), they asked why these people accumulate so much fat, and why they accumulate it when and where they do.

comparison. But if we switch to plant-based eating and remain fat and/or diabetic anyway, or if we’ve been eating vegetarian or vegan all along, or mostly plants, and have become fat and/or diabetic, then it’s likely that meat and animal products are not our particular problem, or at least not the principal problem, and it behooves us to correctly identify what is.

Here’s the British endocrinologist Raymond Greene’s version from his seminal 1951 textbook The Practice of Endocrinology: Foods to be avoided: 1 Bread, and everything else made with flour 2 Cereals, including breakfast cereals and milk puddings 3 Potatoes and all other white root vegetables 4 Foods containing much sugar 5 All sweets

You can eat as much as you like of the following foods: 1 Meat, fish, birds 2 All green vegetables 3 Eggs, dried or fresh 4 Cheese 5 Fruit, if unsweetened or sweetened with saccharin, except bananas and grapes

They resulted not just in weight loss free from hunger, but in weight loss without the other consequences of a body that is being starved for fuel—fatigue

A primary function is indeed to keep blood sugar under control, but the relevant point for our purposes is that one way it accomplishes that is by also promoting the storage of fat.

Not too little, too much. Older patients with obesity and diabetes weren’t suffering

Insulin resistance turns out to be fundamental to both obesity and type 2 diabetes—type 2 diabetes more or less is insulin resistance—and all the chronic diseases associated with them. When we are insulin resistant, our bodies (the pancreas, specifically) produce more and more insulin trying to achieve the necessary blood sugar control.

that insulin will do what insulin does, which is signal fat cells to store fat.

and suggesting that the insulin resistance that they were seeing in people with obesity and diabetes might clearly explain why they were fat. When insulin is secreted, it prompts cells throughout the body to take up more blood sugar from the circulation and use it for fuel; it causes liver cells to make fat from glucose and ship that fat out for storage; and it induces fat cells to take up and store any fat for the future.

but lowering the amount of insulin in the circulation. (Eating less and exercising, as I’ll discuss, can be inefficient ways of lowering insulin levels.)

“requires only the negative stimulus of insulin deficiency.”

could be stated “categorically,” they wrote in 1963, that obesity was impossible without adequate levels of insulin and that storing excess fat “cannot take place” without some insulin around to make it happen and, critically, without the body taking in carbohydrates—glucose—to stimulate that insulin secretion.

All diets

that result in weight loss do so on one basis and one basis only: They reduce circulating levels of insulin; they create and prolong the negative stimulus of insulin deficiency.

What I and others are suggesting is that knowing the math is irrelevant. What’s necessary to prevent and treat and maybe even reverse obesity is knowing the endocrinology, the hormonal influences and how those in turn can be influenced by what we eat.

When you eat carbohydrates, you raise insulin, you burn carbohydrates for energy, and you store fat.

As these British biochemists showed, our bodies burn carbohydrates for fuel (specifically glucose, the stuff of blood sugar) when carbohydrates are available, and they burn fat when the carbohydrates have been effectively used up or stored (as a compound called glycogen).

With insulin decreasing, the fat tissue will eventually experience that negative stimulus of insulin deficiency, and the fat cells will release the fat from storage—they will mobilize it—and we will burn that fat for fuel.

That’s what the body considers a benign amount of blood sugar. That’s about four or five grams’ worth of glucose in your blood or about twenty calories’ worth. You’ll be diagnosed as diabetic if your blood sugar levels while you’re fasting (i.e., in the morning, before breakfast) are even moderately above that level: maybe a teaspoon and a half of glucose, or the equivalent of about thirty total calories of glucose circulating throughout your entire body.

Once that happens and the tide of blood sugar begins to rise, the glucose stimulates the pancreas to secrete still more insulin. All through this process, the insulin is inducing cells in lean tissue and organs to take up the glucose as quickly as possible, and to store or burn it up for fuel. It’s causing those cells to burn glucose rather than fat (fatty acids), and it’s stimulating fat cells to take up and continue to hold on to fat.

Once the carbohydrate situation is under control, the tide of insulin drops (or it does if you’re healthy); the fat cells now see the negative stimulus of insulin deficiency and release fat into the circulation, where the cells of lean tissues and organs can and will take it up and use it for fuel. The same insulin deficiency signal causes cells of lean tissues and organs to also burn the fat for energy.

All that is fine, except that this wonderfully dynamic system is dependent on insulin and the negative stimulus of insulin deficiency to function correctly, and that signal can be disrupted with relative ease by what we eat and how we live in our modern world.

Excess fat, specifically above the waist, is an exceedingly good sign of insulin resistance, in which case insulin is indeed elevated higher than it should be and elevated for longer than it should be.

As you can see, everywhere the fat tissue is taking up fat, it’s insulin that’s promoting it—“Insulin +” as it’s labeled. When the fat tissue is mobilizing fat, getting fat out of the cells and into the circulation where it can be used for fuel, it’s insulin that’s inhibiting it (“insulin –”) and other hormones (adrenaline, noradrenaline, and ANP in the diagram) that are doing the promoting. (Frayn’s Metabolic Regulation, too, goes on to blame human obesity on eating too much.

That actually oversimplifies the reality: Insulin is the signal that the body has been fed carbohydrates. The fat we eat won’t stimulate insulin secretion.

We have to create that negative stimulus of insulin deficiency, which means not eating carbohydrates.

(The reality is that virtually all hormones, with the notable exception of insulin, are technically fat-mobilizing hormones, although they won’t mobilize fat when insulin is elevated. The insulin signal overrides that of these other hormones.)

Ketones are molecules that are synthesized in liver cells when those cells are burning fat for fuel.

That the brain and heart reportedly run more efficiently on ketones than on glucose suggests they may be an ideal fuel for the human body.*1

Atkins diet removes all carbohydrates other than those stored as glycogen in meat and the minimal carbohydrates in green vegetables. Most green vegetables fall into the category that nutritionists used to call 5 percent vegetables, which means only 5 percent of their weight comes from carbohydrates that we can digest and the rest is mostly water and some “roughage,” which we now call fiber and which we barely digest to make use of for fuel.

“the critical carbohydrate level,” and the point of his diet was to remain under that threshold.

keto—you must understand that several conditions must be fulfilled for your liver to synthesize detectable levels of ketones. It has to be burning fat at a high rate, which means insulin levels have to be very low, and that means carbohydrates have to be at least mostly absent from the diet and blood sugar levels have to be at a healthy minimum. One of the many things insulin does is shut down your liver’s synthesis of ketones.

blood sugar drops, though, and the insulin in the circulation also drops (as it should if you’re healthy), fat is mobilized from fat tissue and the liver cells burn that fat.