Living Low Carb (14 page)

The research, published in the December 2008
Annals of Neurology
,
^*
focused on a particular section of the hippocampus—an area of the brain associated with memory and learning. This section—the dentate gyrus—is typically affected by changes seen with aging.

“In this study, we were able to show the specific area of the brain that is impacted by rising blood sugar,” said Scott Small, MD, the lead researcher on the study, which was partly funded by the National Institute on Aging. Using special high-resolution brain imaging, Small and his team found that rising blood sugar was directly associated with decreased activity in the dentate gyrus.

The result: you forget where you put your keys!

The important point here is that the research strongly suggests that keeping blood sugar under control could be the key to preventing “senior moments” and lapses in memory, even in healthy individuals with no hint of diabetes!

“Our findings suggest that maintaining blood sugar levels, even in the absence of diabetes, could help maintain aspects of cognitive health,” said Small.

Two of the most effective measures to manage blood sugar are exercise and a controlled-carb diet!

^*
S. A. Small,
Annals of Neurology
, December 2008; online edition

The body does have basic glucose (sugar) requirements. The brain, for example, needs about 150 to 200 grams of glucose daily. If you’re eating only about 20 grams of carbs a day—probably the lowest amount you would consume on the first phase of the strictest diets—where does the other 130 to 180 grams of glucose come from? Equally important, where does the body get the
rest
of the fuel it needs for its many other metabolic activities, such as exercise and breathing?

Well, the body gets sugar from a process called
gluconeogenesis
, a word that literally means “the creation of new sugar.” Gluconeogenesis is a metabolic process by which sugar is created from
noncarbohydrate
sources. For example, the body will make sugar by using the glycerol molecule in triglycerides (making sugar from fat). It will also make some sugar from protein (e.g., from certain amino acids). And here’s the really good news for the overweight person: if carbohydrates in the diet are sufficiently limited, the majority of the fuel the body needs for its day-to-day operations will come from fat, specifically from a breakdown product of fat called
ketones
.

The body loves ketones. The heart works fine on them, and so does the brain. Here’s how they work. Fats are oxidized, or broken down, by a process called beta-oxidation, in which the long chain of carbons that constitutes a fatty acid is split into pairs of two carbon molecules each, called acetyl fragments. These acetyl fragments join with a compound called CoA (coenzyme A) to form the appropriately named acetyl CoA. Incidentally, acetyl CoA is also the end product of the breakdown of carbohydrates, so both carbohydrates and fats eventually wind up as acetyl CoA.

When there are enough carbs in the pipeline, the acetyl CoA do-si-do’s into something called the Krebs cycle, in which the acetyl CoA is burned for energy. But if there’s not enough sugar, acetyl CoA doesn’t get its allaccess pass into the Krebs cycle. Instead, it accumulates at the door and eventually turns into three ketone bodies (first acetoacetic acid, then betahydroxybutyric acid and acetone, for the science-minded among you). Most of these ketone bodies are sent to the tissues—including the heart and brain—to be used for energy, and some are excreted in the urine and breath. This is what the low-carb diets that stress ketosis are talking about when they speak of changing from a sugar-burning metabolism to a fat-burning metabolism. Ketones are the by-product of fat breakdown.

Ketosis—which happens when there are enough of these ketones to be detectable in the urine—is a topic of such misunderstanding, controversy, and criticism that it will get a much fuller discussion later on. For now, let’s just say that this process is a part of normal metabolism and is not—I repeat,
not
—dangerous.

Ketosis is
not necessary
for weight loss. You could be in ketosis and not lose weight, just as you could lose weight without being in ketosis. You won’t burn your stored fat (and the ketone bodies made from it) if you have a surplus of fuel coming into the pipeline from the food you’re eating. If you’re eating 10,000 calories of fat and no carbs, you’ll definitely be producing a ton of ketones, but you won’t lose a pound. However, if you are eating a moderate number of calories
and
you are in ketosis, it is a good sign that you are burning fat and not sugar as your primary energy source.

If you switch to a higher-fat, higher-protein, lower-carb (and higherfiber!) diet, you won’t have enough sugar coming in to burn as fuel, and your body will have to make its own, mostly from fat and certain amino acids, and/or happily use ketones as fuel. If calories are at reasonable levels at this point—which they probably will be because you’ll be a lot less hungry and have a lot fewer cravings—you will lose weight. You will also improve your blood-lipid profiles (lower triglycerides, higher HDL)
and
your insulin sensitivity. Not only will you get slimmer, but your risk for heart disease, diabetes, and hypertension will plummet.

Not a bad deal, right?

How a Low-Carb Diet Keeps You Healthy and Slim

We’ve talked about what sugar does to the body and why eliminating it is such a good idea. Obviously, a low-carb diet removes a great deal, if not all, of the refined sugar you’ve probably been eating. The health benefits of this reduction are enormous. But a low-carb diet can also remove two other substances that are a huge problem, albeit for very different reasons. One is trans-fats. The other is wheat.

The subject of trans-fatty acids is one of the hottest topics in nutrition today and has been the center of a great deal of debate in the area of public policy regarding food and food labeling. It has been discussed extensively elsewhere, particularly in the writings of Dr. Mary Enig, a lipid biochemist widely considered to be the leading authority on trans-fats in the country, if not the world. For now, let’s just say that in the opinion of many experts, saturated fats have gotten a raw deal and have in fact been blamed for damage done, for the most part, by trans-fats. We know that trans-fats raise LDL cholesterol, probably way more than saturated fats do, and that these damaged trans-fats actually
increase
the risk for type 2 diabetes.
³⁷
They also lower HDL cholesterol and raise the risk for heart disease. A prediction was made in the prestigious medical journal
Lancet
as far back as 1994 that trans-fats would turn out to be a major factor in insulin resistance;
³⁸
that was the same year that the Center for Science in the Public Interest petitioned the FDA to require that Nutrition Facts labels disclose amounts of trans-fat. On July 10, 2002, the National Academy of Science’s Institute of Medicine issued a report that concluded that “the only safe intake of trans-fats is
zero
.” After much hemming, hawing, and stalling, the FDA finally mandated that trans-fat content be listed on food nutrition labels, a ruling that went into effect in 2006.

The intelligent low-carb diet is almost
always
naturally low in transfats, which may be one of the many reasons it can impart such health benefits. Consider this: the top sources of trans-fats are baked goods, muffins, cakes, cookies, doughnuts, granolas, crackers, pies, fast food, french fries, anything deep-fried, partially hydrogenated vegetable oils, and most margarines. The intelligent low-carb diet naturally contains almost none of these foods—or, if it does, they are present in extraordinarily low amounts. The health benefits of this fact alone are incalculable.

After learning of the dangers of trans-fats, I began avoiding fast-food lunches—it’s better for me and my kids.
—Gina D.

The other ingredient that is either missing in action or has an extremely low profile on the low-carb diet is wheat. Now, most people are probably under the impression that wheat and grains are “good” for you. Maybe; maybe not. Certainly, foods made with whole grains—which are far harder to find than you might think and most certainly do
not
include most commercially available “wheat breads”—are better than foods made with the refined grains that constitute the vast majority of grains we eat. But grains, particularly wheat, have a high propensity for turning into sugar quickly, and wheat is also one of the foods most likely to be implicated in food sensitivities.
³⁹
At one point, it was believed that celiac disease—an intolerance of gluten, which is found in most grains—was fairly rare, affecting only 1 in 1,700 people. Estimates are now running closer to 1 in 85, with some estimates as high as 1 in 33.
⁴⁰
And this doesn’t include the hard-to-estimate number of people who have delayed food sensitivities, very often to grains in general or at the very least to wheat. A recent book by clinician James Braly suggests that gluten insensitivity may affect tens of millions of Americans.
⁴¹

Dr. Joseph Mercola, medical director of the Optimal Wellness Center in Illinois, contends that grains—along with starches and sweets—trigger a “hormonal cycle of grain and sugar addiction, weight gain, and diabetes.”
⁴²
And numerous studies link carbohydrates that have a high glycemic load—the tendency to turn into sugar quickly—with increased risk of coronary heart disease
⁴³
and with risk of type 2 diabetes.
⁴⁴
Most high-glycemic processed grains fall into this category, but these grains are virtually eliminated on low-carbohydrate diets.

Insulin: The Smoking Gun

Controlling insulin is the number one priority of all low-carb diets. The dietary approaches discussed in
chapter 3
differ only in how they go about accomplishing it—what degree of carbohydrate restriction they believe is necessary to successfully control insulin, whether they emphasize protein or fat (or both) in the diet, what kinds of fat they recommend, other aspects of metabolism they stress, and whether or not they include a component on emotional eating and holistic self-care.

Once you understand what runaway insulin levels and unregulated sugar metabolism in general can do to your health, it’s easy to understand why correcting those imbalances brings about not only weight loss but a myriad of wonderful health benefits.

In
chapter 7
, we’ll explore exactly how a number of popular diet plans approach the issue of insulin control, and you’ll be able to determine which one is best for you. But first, let’s dispel a few myths about fat, cholesterol, and health.

CHAPTER 3

Fat, Cholesterol,
and Health: Have
We Been Misled?

F
at is the Rodney Dangerfield of the modern diet: it “don’t get no respect.”

For years we tried to eliminate it from what we eat, even though it’s been a basic (and necessary) part of our diet since at least the first recorded
Homo sapiens
in Africa about 200,000 years ago, and likely from the beginning of the genus Homo roughly 2.4 million years ago. More recently, experts have begun—almost grudgingly, it seems—to admit that
some
fat is good, but a good number of them still continue to recommend that you reduce it as much as possible. (And—with the exception of the universally appreciated omega-3 fats—many experts are still for the most part woefully uninformed about which fats are actually “good” and why.) It’s common for health-conscious people to collapse the terms “healthful” and “low-fat” as if they were synonyms (trust me, they’re not). And the majority of fitness books continue to repeat low-fat nonsense that should have gone out of style a decade ago.

So it’s probably safe to say that fat is the single most misunderstood component of the modern diet. And our thinking about fat deeply colors the way we think about low-carb diets.

Here’s why: Suppose, for the moment, that you’re eating a typical American diet of 2,500 calories (or more), of which about half (or more!) comes from carbohydrates. If you remove a big chunk of the carbohydrates from your diet (the definition of a low-carb program, right?), one of two things
has
to happen: One, you simply cut out the carbs but keep everything
else
the same, effectively eating half as much food as before (this never happens). The second much more common and realistic option is that you replace some or all of those carbohydrate calories with something else.

Since there are only three other calorie-containing substances on the planet that you can replace those carbs with (protein, fat, or alcohol) and since most people don’t replace their carbohydrates with a fifth of vodka, chances are your controlled-carb diet is now higher in either protein or fat (or both) than it was before and some Registered Dietitian will soon be screaming bloody murder about how dangerous your diet is because of “all that fat” and how you will quickly die of heart disease.

So, as you can see, it’s all but impossible to speak about low-carb diets and evaluate them properly without treading on a lot of preconceived ideas about fat.

In case you’ve just joined us from another planet and haven’t heard the argument that’s been repeated ad infinitum for the last few decades, here it is in a nutshell: low-carb diets are bad
because
they have too much fat, and too much fat (especially saturated fat) is bad
because
fat raises cholesterol, and high cholesterol is bad
because
it increases the risk for heart disease.