The Paleo Diet (4 page)

When low-carbohydrate diets cause weight loss in the long run (weeks or months), it’s because more calories are being burned than consumed, plain and simple. Low-carbohydrate diets tend to normalize insulin metabolism in many people, particularly in those who are seriously overweight. This normalization prevents swings in blood sugar that, in turn, may cause some people to eat less and lose weight. It is the cutback in total calories that lowers total cholesterol and low-density lipoprotein (LDL) cholesterol (the bad cholesterol) levels. Also, reductions in dietary carbohydrates (whether calories are cut or not) almost always cause a decline in blood triglycerides and an increase in blood high-density lipoprotein (HDL) cholesterol (the good cholesterol).

So, if low-carbohydrate diets cause someone to consume fewer calories, they may help produce weight loss and improvements in blood chemistry, at least over the short haul. However, dieters beware: when low-carbohydrate, high-fat diets are followed
without
a decrease in the daily consumption of calories, they are, according to the American Dietetic Association, “a nightmare.” Let’s see why.

Despite what anybody tells you—despite the outrageous claims of the low-carbohydrate, high-fat diet doctors—if you eat a lot of the saturated fats found in cheeses, butter, and bacon and don’t cut your overall calorie intake, your cholesterol will go up. The medical community has known this for more than fifty years. It’s been demonstrated in metabolic ward studies, in which people are locked into a hospital wing and only allowed to eat foods that have been carefully weighed and analyzed. Many of the low-carbohydrate diet doctors claim that these clinical trials are invalid because none of them reduced the carbohydrate content sufficiently. These doctors should know better; low carbohydrates don’t guarantee low cholesterol.

Dr. Stephen Phinney and colleagues from the Massachusetts Institute of Technology conducted a normal caloric intake metabolic ward trial involving nine healthy, lean men. These men consumed nothing but meat, fish, eggs, cheese, and cream for thirty-five days. They had a low carbohydrate intake—less than 20 grams a day—but it didn’t matter. Their blood cholesterol levels still went up, from 159 to 208 on average in just thirty-five days. This study indicates that diets high in a specific saturated fat called palmitic acid tends to raise blood cholesterol levels when caloric intake levels are normal.

So, at best, low-carbohydrate, high-fat diets are a temporary fix. At worst, they can cause big trouble in the long run by elevating LDL cholesterol levels, which increases the risk for heart and cardiovascular disease.

One major difference between the Paleo Diet and the low-carbohydrate, high-fat diets we just talked about is the fats. In most modern low-carbohydrate weight-loss diets, no distinction is made between good fats and bad fats. All fats are generally lumped together; the goal is simply to reduce carbohydrates and not worry about fats.

But you
should
worry about fats. Not all fats are created equal, and the impact of fat on blood cholesterol—and the odds of developing heart disease—can’t be ignored. The problem is, fats are confusing for many people trying to make good dietary decisions. For one thing, many of them sound alike. How are saturated fats different from monounsaturated—or even polyunsaturated—fats? How are omega 6 fats different from the omega 3 variety?

People in the Paleolithic Age ate a lot of monounsaturated fats; they had saturated and polyunsaturated fats in moderation—but when they did have polyunsaturated fats, they had a proper balance of the omega 3 and omega 6 fats. They consumed far fewer omega 6 polyunsaturated fats than we do today. In addition, the main saturated fat in wild animals was healthful stearic acid, not the cholesterol-raising palmitic acid, which dominates the fat of feedlot cattle.

How important are fats in the diet? Here’s a modern example: People who live in Mediterranean countries, who consume lots of olive oil, are much less likely to die of heart disease than Americans or northern Europeans, who don’t consume as much olive oil. Instead, our Western diet is burdened by high levels of certain saturated fats, omega 6 fats, and trans fats and sadly lacking in heart-healthy, artery-protecting omega 3 fats.

Our studies of hunter-gatherers suggest that they had low blood cholesterol and relatively little heart disease. Our research team believes that dietary fats were a major reason for their freedom from heart disease.

In the first edition of
The Paleo Diet
, I was adamant that you should avoid fatty processed meats such as bacon, hot dogs, lunch meats, salami, bologna, and sausages because they contain excessive saturated fats, which raise your blood cholesterol levels. That message still holds true today, but new information subtly alters this fundamental point of Paleo Dieting, and, as always, the devil lies in the details. Should you now go out and eat bacon and processed meats to your heart’s desire? Absolutely not! Processed meats are synthetic mixtures of meat (muscle) and fat combined artificially at the meatpacker’s or butcher’s whim, with no regard for the true fatty acid profile of wild animal carcasses that our hunter-gatherer ancestors ate. In addition to their unnatural fatty acid profiles (high in omega 6 fatty acids, low in omega 3 fatty acids, and high in saturated fatty acids), processed fatty meats are full of preservatives such as nitrites, which are converted into potent cancer-causing nitrosamines in our guts. To make a bad situation worse, these unnatural meats are typically full of salt, high-fructose corn syrup, wheat, grains, and other additives that have multiple adverse health effects.

So, artificially produced, synthetic, factory meats have little or nothing to do with the wild animal foods our hunter-gatherer ancestors ate, and they should be avoided. But how about the unprocessed fatty meats that we routinely eat, day in and day out, that are produced in feedlots and butchered without adding fats or preservatives? These are meats such as T-bone steaks, spareribs, lamb chops, and chicken legs and thighs, as well as fatty cuts of pork and other fatty domestic meats. Are they a problem?

I realize that many, perhaps most, readers are not hunters and have never seen carcasses of wild animals, such as deer, elk, or antelope. Nor have you had the opportunity to visually contrast the carcasses of feedlot-produced animals to wild animals. I can tell you that there is no comparison. My research group and I have taken the time to do the chemical analyses between wild and feedlot-produced animals, and we have published our results in some of the top nutritional journals in the world.

Wild animal carcasses are lean, have little external fat, and exhibit virtually no fat between the muscles (marbling). In contrast, feedlot-produced cattle maintain a four- to six-inch layer of white fat covering the animal’s entire body. These artificial products of modern agriculture are overweight, obese, and sick. Their muscles are infiltrated with that fat that we call marbling, a trait that improves flavor but makes the cattle insulin resistant and in poor health, just like us. Wild animals rarely or never exhibit marbling.

Because feedlot-raised animals are exclusively fed grains (corn and sorghum) in the last half of their lives, their meat has high concentrations of omega 6 fatty acids at the expense of health-promoting omega 3 fatty acids. The meat of grain-fed livestock is vastly at odds with that of wild animals. Check out Appendix B in this book. A 100 gram (~ ¼4 lb.) serving of T-bone beefsteak gives you a walloping 9.1 grams of saturated fat, whereas a comparable piece of bison roast yields only 0.9 grams of saturated fat. You would have to eat ten times more bison meat to get a similar amount of saturated fat than the amount in a single serving of T-bone steak.

It would be difficult for our hunter-gatherer ancestors to eat anywhere near the amount of saturated fat that we get on a yearly basis in the typical Western diet. So, does dietary saturated fat promote heart disease? Should Paleo Dieters try to limit the fatty domesticated meats in their diet in order to reduce saturated fat? This question is not as clear-cut as it seemed twenty-five years ago, when Drs. Michael Brown and Joseph Goldstein of the University of Texas Southwest Medical Center were awarded the Nobel Prize in medicine for discovering that saturated fats down-regulated the LDL receptor. Their discovery and subsequent randomized, controlled human trials have unequivocally shown that certain saturated fats (lauric acid [12:0], myristic acid [14:0], and palmitic acid, [16:0]) but not all (stearic acid [18:0]), elevate blood cholesterol levels in humans, all other factors being equal. These facts are undeniable. Yet the next question is contentious and has divided the nutritional and medical community in recent years: do increased blood cholesterol levels necessarily predispose all people to an increased risk for cardiovascular disease?

As the scientific community has struggled with this question during the last few years, we should remember that the evolutionary template will almost always guide us to the correct answer. The clogging of arteries that eventually results in fatal heart attacks comes about through a process called atherosclerosis, in which plaque (cholesterol and calcium) builds up in the arteries that supply the heart itself with blood. It was originally thought that this buildup gradually narrowed and finally closed the arteries supplying the heart, thereby causing a heart attack. We now know that this model is inaccurate and too simple.

In the last ten to fifteen years, it has become apparent that inflammation is involved at every step of the way when arteries become clogged with plaque. In fact, the fatal event causing a heart attack is not the gradual narrowing of arteries supplying the heart but rather the rupturing of the fibrous cap that surrounds and walls off plaque that forms in the heart’s arteries. Chronic low-level inflammation triggers the fibrous cap to rupture, which in turn causes a clot to form in the arteries that supply the heart, resulting in a heart attack. Without chronic low-level inflammation, heart attacks probably would rarely or never occur.

So, do dietary saturated fats from fatty meats cause the artery-clogging process known as atherosclerosis? If we look at the evolutionary evidence, the answer is a resounding yes. Dr. Michael Zimmerman, a pathologist at Hahnemann University in Pennsylvania, had the rare opportunity to perform autopsies on a number of Eskimo mummies that had been frozen in Alaska’s permafrost for hundreds of years. The first mummy was that of a fifty-three-year-old woman whose body washed out of the frozen banks of Saint Lawrence Island in October 1972. Radiocarbon dating indicated that she had died in 400 A.D. from a landslide that had completely buried her. Dr. Zimmerman’s autopsy revealed moderate atherosclerosis in the arteries supplying her heart but no evidence of a heart attack. The second frozen mummy was also a female, forty to forty-five years of age, who had also been engulfed in an ice-and-mud-slide in 1520 A.D. near Barrow, Alaska. Similarly, the autopsy showed atherosclerotic plaques lining the arteries of her heart.

From my prior studies of worldwide hunter-gatherers, we know that these Eskimo women had a diet that consisted almost entirely (97 percent) of wild animal foods, including whales, walruses, seals, salmon, muskoxen, and caribou. Because they lived so far north (63 to 71 degrees north latitude), plant foods simply were unavailable; consequently, their carbohydrate intake was virtually zero. Yet they still developed atherosclerosis. Perhaps Drs. Brown and Goldstein were right, after all: high dietary intakes of saturated fats do promote atherosclerosis. Despite these facts, the best archaeological and medical evidence shows that Eskimos living and eating in their traditional ways rarely or never died from heart attacks or strokes.

So, now we have the facts we need to come to closure with the saturated fat-heart disease issue. Dietary saturated fats from excessive consumption of processed fatty meats and feedlot-produced meats increase our blood cholesterol concentrations, but unless our immune systems are chronically inflamed, atherosclerosis likely will not kill us from either heart attacks or strokes.

The new advice I can give you is this: If you are faithful to the basic principles of the Paleo Diet, consumption of fatty meats will probably have a minimal outcome on your health and wellbeing—as it did for our hunter-gatherer ancestors. Consumption of fatty meats and organs had survival value in an earlier time when humans didn’t eat grains, legumes, dairy products, refined sugars, and salty processed foods, the foods that produce chronic low-level inflammation in our bodies through a variety of physiological mechanisms. I will explain this in more depth in my next book,
Living the Paleo Diet
.

A big problem with low-carbohydrate weight-loss diets is what they do to health-promoting fruits and vegetables—they nearly eliminate them. Because of a technicality—a blanket restriction on all types of carbohydrates, even beneficial ones, to between 30 and 100 grams per day—fruits and veggies are largely off-limits. This is a mistake. Fruits and vegetables—with their antioxidants, phytochemicals, and fiber—are some of our most powerful allies in the war against heart disease, cancer, and osteoporosis. Yet just one papaya (59 grams of carbohydrate) would blow the daily limit for two of the most popular low-carbohydrate diets. Eating an orange, an apple, and a cup of broccoli and carrots (73 grams of carbohydrate) —just a drop in the bucket to hunter-gatherers, whose diets were rich in fruits and vegetables—would wreck all but the most liberal low-carbohydrate diets.