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Are carbs really so bad for you?
First, let's take a look at his contention that a high-carb, low-fat diet takes individuals out of the 'zone' of great health and performance. If that were true, then individuals who follow a high-carb, low-fat diet all their lives should be in pretty abysmal health. Likewise, people who eat a la Sears should be hale and hearty with little risk of heart disease, and athletes following the Sears programme should out-compete high-carb athletes. In addition, placing people who have followed a zone diet on a high-carbo plan should hurt their health and athleticism, while putting people who have followed a high-carb routine on a Sears programme should be very productive

Are high-carb people really unhealthy, as Sears contends? Well, let's take a look at the Tarahumara Indians. As you probably know, these people live on the high plateaus of the Sierra Madre Mountains in the state of Chihuahua, Mexico, and follow a very low-fat, high-carbohydrate diet. Most of the Tarahumara's calories come from corn (one of Sears' 'bad' foods), beans, vegetables, and fruits, with small quantities of game, fish, and eggs thrown in. Overall, about 65 to 70 per cent of calories come from carbs, 15 per cent from protein, and 15 to 20 per cent from fat. It's the high-carb, low-fat diet which Sears deplores

Are the Tarahumara healthy? Absolutely. Heart disease is almost unheard-of, high blood pressure is non-existent, and their blood levels of total cholesterol and 'bad' cholesterol (low-density lipoprotein cholesterol, or LDL), which Sears says are magnified by a high-carb diet, are extremely low (to check this out, see The New England Journal of Medicine, vol. 325(24), pp. 1704-1708, 1991)

Can they perform well athletically? The name Tarahumara actually means 'fleet of foot,' and the Tarahumara Indians are as a group the best ultra-distance runners in the world. Tarahumaras routinely run 100 miles without stopping as part of their lifestyle, and they have recently begun to venture into the United States to compete in - and win - important ultra-marathon competitions


What if you changed their diet?
If you decreased the Tarahumaras' carbohydrate intake and boosted their fat intake, would bad things happen? You bet. In fact, that's exactly what was done several years ago by researchers from the Oregon Health Sciences University in Portland. Thirteen Tarahumaras (five women and eight men) gave up their normal diets and followed a modest-carbohydrate, higher-fat eating plan for five weeks. With the richer diet, just 47 per cent of calories came from carbos and 43 per cent originated in fat

After just four days of the reduced-carbo eating, which should have mollified insulin levels, put the damper on bad eicosanoids and taken the Tarahumaras closer to Sears' 'zone' of good health, total cholesterol levels zoomed up by 24 per cent. After seven days, cholesterol was up by 34 per cent. LDL ('bad' cholesterol) shot up by 39 per cent over the five-week period, and plasma triglycerides headed north by about 19 per cent. It wasn't pretty

True, this isn't a totally fair comparison for the Sears 'zone' diet, since total caloric intake also increased in the Portland study. However, the bottom line is that the Tarahumaras are remarkably healthy on their zone-unfavourable diet; when they eat a diet which is more like Sears' zone-favourable programme, their blood-fat profiles become more akin to those of unhealthy Americans

Sears and the Kenyans
And when you look at the elite Kenyan runners, Sears' contentions about diet and athletic performance look even more ridiculous. By Sears' standards, the Kenyans are doing everything wrong. They consume too much carbohydrate, too little protein, and too little fat. Worse yet, the carbs they love - corn, sugar, carrots, potatoes, rice, pasta, bananas, mangos, orange juice, and white bread - are exactly the ones which Sears considers so 'dangerous'. Yet the Kenyans overcome these formidable dietary 'obstacles' to produce the consistently best running performances in the world. I'd bet on the Kenyans and their zone-unfavourable diets every day over a group of Sears-advised endurance runners, who would be eating fewer carbs and would have a much higher risk of glycogen-depleted leg muscles

What about the reverse scenario? If we took a group of people who were eating a low-carbohydrate, moderate- to high-fat diet and put them on a high-carbo plan, would disaster strike, as Sears would predict?
Well, that has been done, and disaster didn't strike. At UCLA, a group of individuals suffering from non-insulin-dependent diabetes mellitus, a group of insulin-resistant persons, and a group of healthy subjects with normal insulin levels were all put on a 'Pritikin' diet composed of 75 to 80 per cent carbohydrate, 10 to 15 per cent protein, and less than 10 percent fat. This is exactly the kind of diet which, according to Sears, has helped to produce the American epidemic of heart disease and obesity

But guess what happened? All three groups decreased their serum levels of insulin, the hormone which Sears says creates so much havoc. All three groups also reduced their total-cholesterol concentrations. All three groups lowered their LDL-cholesterol. All three groups decreased triglyceride levels. All three groups decreased systolic and diastolic blood pressure (25 per cent were able to discontinue hypertensive medication). All three groups decreased body weight

And the improvements weren't small. For example, the insulin-dependent diabetes group cut serum insulin by 33 per cent, systolic blood pressure from 142 to 132, triglycerides by 44 per cent, and body-mass index (an indicator of obesity) by nearly 5 per cent. 55 per cent of the diabetics were able to discontinue their medication. That doesn't sound much like a disaster!

Sears tries to keep up
In contrast, Sears' own efforts to improve the plight of a group of insulin-dependent diabetics by feeding them a 'zone-favourable' (presumably 40-30-30) diet yielded much less impressive results, even though his study went on for twice as long as the UCLA research (see pp. 154-161 of 'The Zone'). Sears' subjects were unable to significantly reduce serum insulin levels (so much for the idea that the zone diet immediately puts you into insulin paradise), knocked down triglycerides by just 27 per cent, lowered systolic blood pressure by 4 per cent (versus 7 percent on the Pritikin diet), and were unable to reduce total cholesterol, which plummeted by 22 per cent for Pritikin people. Total cholesterol is perhaps the most critical risk factor for heart disease; for each 1-per cent reduction in cholesterol, you get about a 2-per cent reduction in risk. This means that Pritikin's people cut their risk by 44 per cent, while Sears' subjects carved their risk by ........ well .......zilch

Finally, let's examine Sears' contention that the trend in American eating toward more carbs and less fat has contributed to obesity. First of all, there has been a drop in fat consumption, when fat intake is expressed as a percentage of total calories. In 1978, for example, fat made up about 36 per cent of the American diet. By 1990, it had dropped to 34 per cent (wow!)

However, these figures can be quite misleading. In 1978, the average American was ingesting about 1969 calories per day. In 1990, the figure had soared to 2200 calories each day, a 12-per cent upswing. And that increased overall eating actually meant that in fact Americans were eating more - not less - fat. 36 per cent of 1969 calories (the 1978 figures) adds up to 709 fat calories. 34 per cent of 2200 calories (the 1990 numbers) adds up to 748 calories, a 39-calorie increase in fat consumption per day. That upswing in fat intake alone can explain the American advance in fatness, especially when you consider that Americans were becoming more sedentary during this same time period. Also notice that the current 34-per cent figure, the one associated with extremely high rates of obesity and heart disease, is not far from the 30-per cent benchmark suggested by Sears, but of course is far above the 15-per cent level of the Tarahumara, the 10-per cent level of the Kenyans, and the less-than-10 per cent fat content of the Pritikin people

Other aspects of 'The Zone' are also bother-some. Sears continually describes anecdotal reports of athletes who went on the zone-favourable diet and suddenly became super-performers, or disease-stricken individuals who became well after 'entering the zone'. These anecdotal reports just don't cut it; the bottom line is that the well-controlled research described above doesn't support Sears' ideas

Sears' perspective is also sometimes unsettling, as when he describes his early attempts to use phospholipids to remove plaque from the insides of laboratory-animals' artery walls: 'But a slight complication was occurring - some of the animals were dying'. (p. xii) Is death really just a 'slight complication'?

Now, a few pluses
There are good things in the book: For example, Sears' description of the behaviour of major drug companies appears to be right on. He describes a case in which a major drug company discovered that injecting certain phospholipids into the bloodstream removed atherosclerotic lesions. As Sears points out, this should have triggered 'a furious race among the giant drug companies to develop and market phospholipids as a treatment for heart disease in humans. But it didn't. The drug manufacturers had a business problem: phospholipids are natural substances, and it's impossible to get a patent (and therefore all the profits - ed.) for something that occurs in nature. Without the possibility of the exclusive rights a patent confers, the drug companies ..... were not interested.' (p. xi)
And Sears is also right when he asserts that when we select food to put into our mouths, we are making a very important decision about how we want our bodies to work. The problem is that the zone-favourable diet he recommends has not been convincingly linked with optimal health or performance


What's the final word?
High-carb, low-fat diets are not the guaranteed tickets to the coffin that Sears says they are. In fact, they are unequivocally the diets associated with highest-possible athletic performances, and research also links them with better blood-fat profiles and a lower risk of heart disease. What Sears says about high-glycaemic-index and low-glycaemic-index carbohydrates does contain a grain of truth, however, especially for 'reactive' people whose blood-sugar levels behave like a roller coaster whenever they take in the easily and quickly absorbed carbos. Especially for those people, it's probably wise to gradually introduce more low-index carbs into their diets, while taking away some of the high-index ones. If you are currently eating a low- to moderate-carbohydrate diet, it's also wise to shift over to higher carbohydrate intakes gradually. You may indeed 'bonk' if you suddenly engage in a flurry of sugar, rice-cake, potato, and corn-flake eating. But the bottom line is that high-carb, low-fat eating is the way to go - both for your performance and your health.

Owen Anderson

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