UC Berkeley School of Public Health

Eat Fat, Get Thin?
UC Berkeley Wellness Letter, April 2000
Eat Fat, Get Thin?

Founded in 1984, the UC Berkeley Wellness Letter has more than 350,000 subscribers in the U.S. and Canada (plus thousands of readers of its foreign-language editions). It has been rated No. 1 by U.S. News & World Report, the Baltimore Sun, Money Magazine, and the Washington Post, for its “brisk,” “reasoned” coverage of health issues. The Wellness Letter relies on the expertise of the School of Public Health and other researchers at UC Berkeley, as well as other top scientists from around the world.

There’s nothing new or revolutionary about Dr. Atkins’ New Diet Revolution, which has been a bestseller for several years. Dr. Robert Atkins has been pushing his high-protein, high-fat, low-carbohydrate diet for 30 years. Now other diet doctors (Eades, Sears, and Heller) and celebrities (Suzanne Somers) are advocating their own low-carb variations. Such diets have actually been around for at least a century, reappearing every decade or two, but they have never been more popular than today. Newspapers, books, TV shows, and infomercials offer testimonials from happy “carbohydrate dropouts.” Why is this diet craze booming? In part, it is a backlash against established nutritional wisdom with its emphasis on a high-carbohydrate diet. In addition, these diets tend to work, at least for a while.

During the first two weeks of the Atkins diet you eat as much fat and protein—beef, poultry, eggs, bacon, cheese, etc.—as you like. But you can eat no more than 20 grams of carbohydrates (that is, sugars and starches) a day; that’s the amount in two small slices of bread or one apple. But you can’t consume any bread, rice, or other grain products, fruit, starchy vegetables, or milk. That small amount of carbohydrates can come only from a few vegetables, such as asparagus, broccoli, and cabbage. Eventually, in the “maintenance” phase, you’re allowed 40 to 90 grams of carbohydrates—15 to 30% of the amount you would eat on a heart-healthy, high-carbohydrate diet. The rest is all fat and protein.

No wonder you lose weight

During the first two weeks on this diet your weight loss can be precipitous, since much of it is water. In addition, your body will burn its 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 often depresses appetite and may cause nausea. Dr. Atkins considers this state normal, even “benign.” Ketosis is indeed the body’s way to adapt to this abnormal situation, as it would to fasting. But ketosis poses potential dangers (see below).

If you lose weight on Dr. Atkins’ plan after the first two weeks, it’s because it ultimately 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. Putting a limit on the variety of foods makes meals boring, so dieters lose interest and end up eating less, especially if ketosis continues. Cut calories, lose weight—surprise, surprise.

So why not?

If you stay on the Atkins diet for a few weeks, with the proper supplements, it can be safe. You may have adverse effects though: dehydration, dizziness, constipation, weakness, and headaches. If you remain on the diet very long, even its maintenance phase, you face more serious risks:

• Ketosis will increase blood levels of uric acid—a risk factor for gout and kidney stones in susceptible people.

• Though Dr. Atkins claims that his diet reduces cholesterol and lowers the risk of heart disease, any diet very high in saturated fat is likely to boost blood cholesterol. (However, in the early stages of the diet, you actually may not consume more fat than usual, since you eat less food.) In addition, ketosis may damage LDL (“bad”) cholesterol, making it more likely to stick to artery walls and increasing the risk of a heart attack.

• High-protein diets in general can lead to calcium loss from the body, possibly decreasing bone density and increasing the risk of osteoporosis. This risk is greater if the diet is low in fruits and vegetables, which supply nutrients essential for bone health.

• You can’t get the vitamins, minerals, and fiber you need on this diet, so Dr. Atkins recommends supplements—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, and may not get all the vitamins and minerals you need.

• People with medical problems should be monitored by a doctor when trying any crash diet, especially this one. The rapid weight loss and dehydration can affect the action of medications (notably those for hypertension).

But what about all the “evidence” cited by Dr. Atkins (and other diet doctors)? It’s nearly all anecdotal and misleading. There are no long-term studies showing that a low-carb diet (Atkins or others) is more effective than any other reduced-calorie diet. There is virtually no place on earth where people normally eat a very-low-carb diet, so there’s no long-term safety record. In fact, most people around the world have diets that are much higher in carbohydrates than the typical American diet. In countries, such as Japan, with the thinnest—and generally healthiest—people, the diets consist overwhelmingly of carbohydrates.

Don’t say diet

Dr. Atkins and other low-carb advocates blame the rise in obesity in the U.S. on excessive carbohydrate intake, which they claim causes insulin resistance and thus weight gain. This argument doesn’t hold water. There’s no evidence that eating carbohydrates, especially complex carbohydrates (starches), stimulates appetite or leads to more or easier fat storage and weight gain. And if you do cut down on complex carbohydrates such as grains and vegetables, what are your alternatives? Certainly not more animal fat: the long-term dangers of a diet high in saturated fat are clear.

Fruits, vegetables, and whole grains should be your main foods. Combined with low-fat dairy products and small amounts of lean meats, poultry, and fish, they provide the vitamins, minerals, fiber, and phytochemicals you need. Numerous controlled studies have shown that such a way of eating helps protect against heart disease, diabetes, and several cancers, and aids in weight control. And it’s not a crash diet, but an eating plan that, when combined with exercise, can help you gradually lose weight and then maintain a healthy weight for the rest of your life.

Bottom line: If you follow the Atkins diet, you will lose weight—but it could be dangerous beyond a few weeks. All fad diets get you to cut down on calories, usually by limiting the kinds of food you can eat, so of course you lose weight. Most, like the Atkins diet, deny that “calories count,” but nonetheless trick you into cutting way down on calories by distracting you with strange rules and psychological/biochemical babble. As with all crash diets, keeping the weight off is the hard part. Virtually all crash dieters eventually gain the weight back, unless they learn the basics of healthy eating, which crash diets do not teach.