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Weighing in on the Diet Debate
For: Wellness Made Easy, June 2003

In July 2002 an article in the New York Times, "What If It’s All Been a Big Fat Lie?" by Gary Taubes, set off the latest, and loudest, round in the ongoing debate about low-fat versus high-fat diets. The fact that it generated such an uproar shows the power of the Times. But it also shows that lots of people are worried, confused, and/or angry about their growing waistlines. More than 60% of American adults (and nearly as many Canadians) are now overweight or obese. Taubes says the culprit is the low-fat, high-carbohydrate diet the government and most nutrition experts have advocated. And he proposes that high-fat diets, notably that of Dr. Atkins, may be the solution.

Taubes’s article was filled with half-truths, "what ifs," and muddled science. It presented only one side of the debate—the Atkins side. Still, it raised important questions about the obesity epidemic and the failings of mainstream dietary advice.

Big fat confusions

Taubes and Atkins claim: Americans have shifted to low-fat diets, but have still gained weight.

Fact: Americans are eating just as many grams of fat as they did 20 or 30 years ago, or slightly more. The overall percentage of calories supplied by fat has dropped, but we’ve accomplished that primarily by eating more high-carbohydrate (usually sugary) foods and soft drinks. The proportion of fat in the diet dropped because, while our fat intake has stayed about the same, we’re consuming 300 to 500 more calories a day. That’s a huge difference—and a very unhealthy scenario.

Claim: People gain weight because carbohydrate-rich foods (everything from pasta, bread, and rice to fruits, vegetables, and "sweets") actually make them hungrier.
Fact: There is no evidence that most high-carbohydrate foods stimulate appetite. Sugary or starchy foods, when eaten by themselves, can cause a spike in insulin level, followed by a drop in blood sugar, and thus may leave some people hungry in an hour or two. But not all carbohydrate-rich foods do this, certainly not most vegetables and fruits, beans, and whole grains, or even starchy foods when eaten as part of a balanced meal. Many high-carb foods are filling and satisfying. And by the way, most people who say they crave carbohydrates or have a "sweet tooth" actually overindulge in combinations of fat and sugar, such as cakes and ice cream, not plain sugary foods like jellybeans.

Claim: Excessive intake of carbohydrate causes insulin resistance and thus weight gain.
Fact: It’s estimated that at least 25% of Americans are insulin-resistant—that is, their cells have become less sensitive to insulin, so the body pumps out more of it. This can progress to diabetes and is associated with a common cluster of disorders—obesity, high blood pressure, low HDL ("good") cholesterol, high triglycerides—that has been dubbed Syndrome X or Metabolic Syndrome. But there’s no evidence that carbohydrate-rich foods cause insulin resistance. Moreover, insulin resistance doesn’t make people fat. Most experts believe that insulin resistance is largely a result of obesity, lack of exercise, smoking, and aging, though there’s also a genetic element.

Claim: The calories in carbohydrate-rich foods lead to more or easier fat storage.
Fact: Again, there’s no good evidence for this. A calorie is a calorie, whether it comes from fat, carbohydrates, or protein. And remember, fat contains more than twice as many calories by weight as carbohydrates or protein.

Claim: It has never been proven that a carbohydrate-rich diet can promote weight control or good health.
Fact: Not true. Many studies have shown that the right kind of high-carb diet (see below) can help people lose weight and reduce the risk of heart disease, diabetes, and certain cancers. In most Asian countries, where diets consist overwhelmingly of rice, noodles, vegetables, and other carbohydrate-rich foods, people tend to be thin and have a low risk of major chronic diseases.

Claim: The surging obesity rate can’t be blamed on lack of exercise, since there has been an exercise boom in the U.S. in recent decades.
Fact: Only a small segment of the population is going to the gym, jogging, or even walking briskly. Virtually every survey shows that Americans, on average, have become increasingly sedentary.

Claim: The Atkins diet and other high-fat diets work. In fact, they work better than other diets.
Fact: No one ever claimed that they don’t work in the short term. They work because they are low-calorie diets. You may lose more weight initially, but such diets do not work better than other low-calorie diets in the long term. It doesn’t matter if you cut the calories from fat, carbs, or protein, you’ll lose the same amount of weight. In any case, losing weight is not that hard—keeping it off is.

Atkins: a best-seller again

For 30 years Dr. Robert Atkins has been promoting his high-fat, high-protein, low-carbohydrate diet not only for weight loss, but also for disease prevention. Other diet doctors (Eades, Sears, and Heller) advocate their own variations. Such low-carb diets have actually been around for at least a century.

During the first two weeks of the Atkins diet you eat as much fat and protein—beef, poultry, eggs, bacon, cheese—as you like. But you can hardly eat any carbohydrates (only a few vegetables, such as asparagus, broccoli, and cabbage). You can’t consume any bread, rice, or other grain products, fruit, starchy vegetables, or milk. Eventually, in the "maintenance" phase, you’re allowed slightly more carbohydrates. The rest is all fat and protein.

During the first two weeks on this diet weight loss can be dramatic, since most of it is water, not fat. Because of the calorie reduction, you will burn your own fat. Actually, you burn fat all the time, but without carbohydrates your body does not burn the fat completely, and thus substances called ketones are formed and released into your bloodstream. This condition, called ketosis, makes dieting easier, because it tends to cause nausea, which suppresses appetite. Dr. Atkins considers this state benign, but there’s no evidence for this claim. Ketosis poses potential dangers over the long term.

No wonder you lose weight

If you lose weight on Dr. Atkins’ plan after the first two weeks, it’s because it gets you to cut down on calories, despite his claims that this is not a low-calorie diet. He doesn’t specify quantities, but the food choices are very limited, so you end up eating less, especially if ketosis continues.

Normally, eating lots of highly saturated animal fat boosts LDL ("bad") and total blood cholesterol. But the Atkins diet, because it causes weight loss, may actually reduce cholesterol, according to a recent six-month study at Duke University (subjects averaged only 1,450 calories a day). Other studies have found that such diets can raise cholesterol, at least in many people. Even if your cholesterol level does drop, once you stop losing weight, it will likely climb back up if your diet is high in saturated fat.

Since 1972 Atkins’ books have sold more than 11 million copies. And yet when researchers who compiled the National Weight Control Registry analyzed the diets of 3,000 successful dieters (who lost at least 30 pounds for more than a year), they found that fewer than 1% had used a very-low-carb diet such as Atkins’. If the Atkins diet offered some sort of metabolic advantage for long-term success, surely it would be better represented.

So why not?

There’s virtually no place on earth where people regularly eat such a high-fat, high-protein diet, so there’s no long-term safety record. If you are healthy and stay on the Atkins diet for a few weeks or months, with proper supplements, it may be safe. There are known adverse effects, though: dehydration, constipation, dizziness, fatigue, nausea, and headaches. The longer you remain on the diet, even its maintenance phase, the greater the risks:

• A diet rich in animal fat (and low in plant foods) increases the risk of heart disease, high blood pressure, stroke, diabetes, various cancers (such as colon and prostate), and diverticulosis.

• High intake of animal protein over long periods can increase the risk of liver disorders, and possibly kidney disease and bone loss.

• You can’t get the vitamins, minerals, and fiber you need on this diet, so Dr. Atkins recommends supple-ments—preferably the formulas he markets. But no matter how many pills you take, you won’t get the fiber and the array of protective phytochemicals found only in fruits, vegetables, and whole grains.

• People with medical problems, such as diabetes or high blood pressure, should consult a doctor when trying any diet, especially an extreme one like this.

Bottom line: If you follow an Atkins-style diet, you’ll probably lose weight, but it could be dangerous beyond a few weeks. As with all crash diets, keeping the weight off is the hard part.

The common wisdom: far from perfect

Atkins-style diets have become so popular because of the obesity epidemic and the failure of mainstream dietary advice to slow it during the past two decades. Some of this advice was simplistic, some overly complicated. Much of it has been misunderstood and has had unintended consequences. Here are some key points:

• "Low fat," by itself, is not the answer. Some people may have assumed that if they eat a low-fat diet, they would automatically lose weight. Not so. Low-fat or nonfat cakes, cookies, and ice cream are often high in calories. And if you consume too many calories, whatever the source, they’ll be stored as fat and you’ll gain weight.

• It doesn’t help to talk about "fats" and "carbohydrates"—the terms are confusing. There are good fats and bad fats, good carbs and not-so-good carbs (see below). Moreover, nearly all foods are combinations of various fats, carbohydrates, and protein. It makes much more sense to talk simply in terms of foods—those you should eat more of, those you should cut down on or avoid.

• Exercise is essential to successful weight control over
the long haul.

Our advice: the good-fat, good-carb diet

Diet promoters almost always claim that you have to eat some special combination of foods and/or avoid certain foods to lose weight. This is not true. The facts for weight loss are simple and not surprising. You must reduce the number of calories you consume, burn more calories through exercise, or do both. And to keep the weight off, which is the real trick, you have to make these changes permanent. There is no magic. But it can be done.

The basic healthy way of eating that we recommend can also be adapted for a weight-loss diet. Fruits, vegetables, and whole grains should be your main foods, along with low-fat dairy products, fish, skinless poultry, and lean meats. Such a way of eating helps protect against heart disease, diabetes, and several cancers. It is very similar to the DASH diet, which is proven to lower high blood pressure (see Wellness Letter, June 2002). It can also help with weight control, especially if you limit portion sizes and start to exercise more. It’s not a crash diet, but an eating plan for the rest of your life.

The following advice is for virtually everybody, and especially for those who may have insulin resistance:

• Eat plenty of high-fiber foods—that is, fruits, vegetables, beans, and whole grains. These are the "good carbohydrates"—nutritious, filling, and relatively low in calories. And fiber slows the absorption of the carbohydrates, so there’s less effect on insulin and blood sugar.

• Limit your intake of sugary foods, refined-grain products such as white bread, and salty snack foods. Sugar, our No.1 additive, is added to a vast array of foods. High-fructose corn syrup—an increasingly common form of sugar, especially in soft drinks—now supplies nearly 10% of all calories consumed in the U.S. Just one daily 12-ounce can of soda (160 calories) can add up to 16 pounds over the course of a year. Many sugary foods are also high in fat, so they’re calorie-dense. Plain pasta and bread are not very high in calories, but what’s typically put on top of them (meat or cream sauces, butter, cheese) can double or triple the calories. Potatoes are a problem largely because most are eaten as high-calorie fries or chips.

• Cut down on animal fat. Choose lean meats, skinless poultry, and nonfat or low-fat dairy products.

• Cut way down on trans fats, supplied by hydrogenated vegetable oils used in most processed foods in the supermarket and in many fast foods.

• Eat more fish and nuts, which contain healthy unsaturated fats. Substitute olive or canola oil for butter or stick margarine.

• Keep portions moderate, especially of high-calorie foods. In recent years serving sizes have ballooned, particularly in restaurants. Choose a starter instead of an entrée, split a dish with a friend, and don’t order supersized anything.

• Exercise and be active. Successful weight control and ultimately good health also depend on the other side of the energy equation: the calories you expend in physical activity.

• To increase the chances of long-term success, set realistic goals that lead to a slow, steady weight loss (no more than one or two pounds per week). Studies show that people are more likely to keep the weight off if they lose it gradually.

• If you do go on a crash diet, Atkins’ or another, to "jump start" your weight loss, do it for only a few weeks or months, and then switch to the healthy diet we’ve described. But if you have medical problems, do it under a doctor’s supervision.

UC Berkeley Wellness Letter, November 2002