Why We Get Fat: And What to Do About It (24 page)
Read Why We Get Fat: And What to Do About It Online
Authors: Gary Taubes
Researchers who studied this evidence in the 1950s and 1960s—Thomas “Peter” Cleave and George Campbell, coauthors of
Diabetes, Coronary Thrombosis and the Saccharine Disease
(1966), deserve the most credit—made the point that when isolated populations start eating Western foods, sugar and white flour are invariably the first, because these foods could be transported around the world as items of trade without spoiling or
being devoured on the way by rodents or insects. The Inuits, for example, living on seals, caribou, and whale meat, begin eating sugar and flour (crackers and bread). Western diseases follow. The agrarian Kikuyu, living in Kenya, start eating sugar and flour, and these diseases appear. South Pacific islanders living on pigs, coconuts, and fish start eating sugar and white flour, and these diseases appear. The Maasai add sugar and flour to their diet or move into the cities and begin eating these foods, and the diseases appear. Even the vegetarian Hindus in India, to whom the fleshpot was an abomination, ate sugar and flour. Doesn’t it seem a good idea to consider sugar and flour likely causes of these diseases?
This seems perfectly reasonable to me (and to you, I hope). But it was rejected for the same reason the fattening carbohydrate and carbohydrate-restricted diets were rejected: it clashed with the idea that dietary fat causes heart disease, which had become the preferred hypothesis of nutritionists in the United States. And these nutritionists were simply unaware of the historical and geographical depth of the evidence implicating sugar and flour.
So now we need to revisit the question of whether it’s the fat we eat that really causes heart disease. If dietary fat doesn’t, we should have a pretty good idea what does. In the next chapter, I’ll look at what the latest research shows concerning this question of the dietary causes of heart disease, not to mention diabetes, cancer, and the other diseases of Western diets that we would like to avoid.
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It was Donaldson’s diet that led Alfred Pennington to treat DuPont executives with mostly meat diets in the late 1940s, and Pennington’s work that led Herman Taller, a New York obstetrician, to write
Calories Don’t Count
, which became one of the most controversial diet books ever written and, in the process, shaped much of the debate, still ongoing obviously, about carbohydrates and carbohydrate-restricted diets.
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By Loren Cordain et al.; see
Sources
.
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The same behavior is typical of carnivores. Lions, for instance, will eat the fat organ meat of their kills and leave the “lean muscle meat” for scavengers.
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In 1997, John Higginson, the founding director of the World Health Organization’s International Agency for Cancer Research, described as a “cultural shock” the experience of training to be a doctor in Europe or North America and then going off to work in one of these non-Westernized societies, as he had done in South Africa a half-century earlier. The physicians discover, he wrote, “that the patterns and pathogenesis of disease … were very different from what they had been accustomed to elsewhere. Moreover, such differences were not confined to the communicable diseases as anticipated, but also the chronic illness such as cancer and heart disease.”
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The meat-eating hypothesis “hardly holds good” in regard to Native Americans, as the Columbia University pathologist Isaac Levin noted in 1910. “They consume a great deal of food [rich in nitrogen—i.e., meat], frequently to excess,” and yet had virtually no cancer, as Levin himself had confirmed in a survey of physicians from the Office of Indian Affairs working on reservations throughout the American West and Midwest.
The Nature of a Healthy Diet
Since carbohydrates make us fat, it follows that the best and perhaps only way to avoid becoming fat is to avoid the carbohydrate-rich foods that are responsible. For those who are already fat, this implies that the best and perhaps only way to become lean again is to do the same. The logic is straightforward. But our doctors believe these diets will do us more harm than good, which makes it a difficult and dangerous proposition to believe otherwise.
Here are the three primary arguments against carbohydrate-restricted diets, the ones that have been made repeatedly since the 1960s:
1) That they’re scams because they promise weight loss without having to eat less and/or exercise, thus violating the laws of thermodynamics and the primacy of calories-in/calories-out.
2) That they’re unbalanced, because they restrict an entire nutrient category—carbohydrates—and the first law of healthy eating is to eat a balanced diet from all the major food groups.
3) That they’re high-fat diets, and particularly high in saturated fat, and will cause heart disease by raising our cholesterol.
Let’s take these criticisms one at a time and see how they stand up.
This needs little more discussion. Much of the antagonism toward carbohydrate-restricted diets, from the earliest days, arises from the belief that proponents of these diets are trying to con a gullible public. Eat as much as you want and lose weight? Impossible.
But we know now what happens when we restrict carbohydrates, and why this leads to weight loss and particularly fat loss, independent of the calories we consume from dietary fat and protein. We know that the laws of physics have nothing to do with it.
The unbalanced diet argument makes little sense if starches, refined carbohydrates, and sugars do indeed make us fat, because it’s hard to argue rationally for anything other than avoiding these carbohydrates to fix the problem. When our doctors counsel us to quit smoking because cigarettes cause lung cancer, emphysema, and heart disease, they don’t care if we find life less fulfilling without them. They want us to be healthy, and they assume we’ll get over the absence, given time. Since these carbohydrates make us fat—and maybe cause a host of other chronic diseases, as I’ll discuss—the same logic holds here.
If you cut back on all calories equally, or preferentially restrict fat calories, as we’re often counseled, you’ll be eating less fat and protein, which are not fattening, and more of the carbohydrates that are. Not only won’t this diet work as well, if it works at all, but hunger will be a constant companion. If you restrict only carbohydrates, you can always eat more protein and fat if you feel the urge, since they have no effect on fat accumulation. As early as 1936, the Danish physician Per Hanssen was pointing out that this was a primary advantage of carbohydrate restriction: if you
can lose weight without hunger, aren’t you more likely to maintain that way of eating than one that requires indefinite semi-starvation?
The argument that a diet that restricts fattening carbohydrates will be lacking in essential nutrients—including vitamins, minerals, amino acids—does not hold up. First, the foods that you would be avoiding are the fattening ones, not leafy green vegetables and salads. This alone should take care of any superficial anxieties about vitamin or mineral deficiencies. Moreover, the fattening carbohydrates that are restricted—starches, refined carbohydrates, and sugars—are virtually absent essential nutrients in any case.
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Even if you believe that weight loss requires cutting calories, these fattening carbohydrates would be the ideal foods to cut for just this reason. If you follow the conventional wisdom and so cut all calories, say, by a third, you’re also cutting all essential nutrients by a third. A diet that prohibits sugars, flour, potatoes, and beer, but allows unlimited meat, eggs, and leafy green vegetables, leaves in all the essential nutrients, as the British nutritionist John Yudkin argued in the 1960s and 1970s, and may even increase them, since you can eat more of these particular foods on such a diet, not less.
Ever since the 1960s, when it was first argued that animal products could be bad for our health because they contain saturated fat, nutritionists have typically refrained from pointing out that meat contains all the amino acids necessary for life,
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all the
essential fats, and twelve of the thirteen essential vitamins in surprisingly large quantities. It’s true nonetheless. Meat is a particularly concentrated source of vitamins A and E, and the entire complex of B vitamins. Vitamins B
12
and D are found
only
in animal products (although we can get sufficient vitamin D from regular exposure to sunlight).
Vitamin C is the one vitamin that is relatively scarce in animal products. But it appears to be the case, as it certainly is for the B vitamins, that the more fattening carbohydrates we consume, the more of these vitamins we need. We use B vitamins to metabolize glucose in our cells. So, the more carbohydrates we consume, the more glucose we burn (instead of fatty acids), and the more B vitamins we need from our diets.
Vitamin C uses the same mechanism to get into cells (where it’s needed) that glucose does, so the higher our blood sugar level, the more glucose enters the cells and the less vitamin C. Insulin also inhibits what’s called the uptake of vitamin C by the kidney, which means that when we eat carbohydrates we excrete vitamin C with our urine rather than retaining it, as we should, and using it. Without carbohydrates in the diet, there’s every indication that we would get all the vitamin C we ever needed from animal products.
This makes sense from an evolutionary perspective as well, since any human populations that lived far enough from the equator to see lengthy winters would have gone months, if not years, at a time—during ice ages, for instance—without eating anything but what they could hunt. The idea that they required orange juice or fresh vegetables to get their requisite vitamin C every day seems absurd. This would also explain why isolated hunter-gatherer populations that ate virtually no carbohydrates and certainly no green vegetables or fruits still thrived.
Carbohydrates are not required in a healthy human diet. Another way to say this (as proponents of carbohydrate restriction have) is that there is no such thing as an essential carbohydrate. Nutritionists will say that 120 to 130 grams of carbohydrates are required in a healthy diet, but this is because they confuse what
the brain and central nervous system will burn for fuel when diets are carbohydrate rich—120 to 130 grams daily—with what we actually have to eat.
If there are no carbohydrates in the diet, the brain and central nervous system will run on molecules called “ketones.” These are synthesized in the liver from the fat we eat and from fatty acids, mobilized from the fat tissue because we’re not eating carbohydrates and insulin levels are low, and even from some amino acids. With no carbohydrates in the diet, ketones will provide roughly three-quarters of the energy that our brains use. And this is why severely carbohydrate-restricted diets are known as “
ketogenic
” diets. The rest of the energy required will come from glycerol, which is also being released from the fat tissue when the triglycerides are broken down into their component parts, and from glucose synthesized in the liver from the amino acids in protein. Because a diet that doesn’t include fattening carbohydrates will still include plenty of fat and protein, there will be no shortage of fuel for the brain.
Whenever we’re burning our own fat for fuel (which is, after all, what we want to do with it), our livers will also be taking some of this fat and converting it into ketones, and our brains will be using them for energy. This is a natural process. It happens any time we skip a meal and, most conspicuously, during the hours between dinner or late-night snack and breakfast, when our bodies live off the fat we stored during the day (or at least should be living off that fat). As the night goes on, we mobilize progressively more fat, and our livers up their production of ketones. By morning, we’re technically in a state known as “ketosis,” which means that our brains are primarily using ketones for fuel.
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This is no
different from what happens on a diet that restricts carbohydrates to fewer than sixty or so grams per day. Researchers have reported that the brain and central nervous system actually run more efficiently on ketones than they do on glucose.
In fact, we can define this mild ketosis as the normal state of human metabolism when we’re not eating the carbohydrates that didn’t exist in our diets for 99.9 percent of human history. As such, ketosis is arguably not just a natural condition but even a particularly healthful one. One piece of evidence in favor of this conclusion is that physicians have been using ketogenic diets to treat and even cure otherwise intractable childhood epilepsy since the 1930s. And researchers have recently taken to testing the idea that ketogenic diets can cure epilepsy in adults as well and even treat and cure cancer (an idea, as I’ll discuss, that’s not nearly as absurd as it might sound).
This is the living-room elephant in any discussions of the risks or benefits of carbohydrate-restricted diets. Nutritionists initially got angry about carbohydrate restriction because they believed that the claims made for these diets were impossible, but this is the one that kept them angry and keeps their minds resolutely closed to any contrary evidence. They believe that if we buy into the logic of these diets, we’ll replace what they consider “heart-healthy” carbohydrates—broccoli, whole-wheat bread, and potatoes, for instance—with meat, butter, eggs, and maybe cheese, which we very well might. Since the latter are all sources of saturated fat, the diets will raise our cholesterol, according to this logic, specifically the cholesterol in LDL (low-density lipoproteins), commonly known as the “bad” cholesterol, and we will have increased our risk of heart attack and premature death. This is the line of reasoning that prompted Jean Mayer to evoke his mass-murder metaphor. It’s why most physicians and medical
organizations still believe—or say they do—that the restricted carbohydrate diets are foolhardy.
There are many reasons to believe that they are wrong.