Nearly everyone knows at least one person who has tried one of today's best-selling high-protein, low-carbohydrate diets; for some, it encompasses their whole circle of friends. Often, it mirrors the domino effect—one person tries the diet, loses a bunch of weight, and all of her friends can't wait to jump on the protein bandwagon.

For example, Marie says she lost 10 pounds on the high-protein diet advocated by Michael and Mary Eades in Protein Power (Bantam Books). And she wouldn't hesitate to do it again. "It took away the lows and highs of my regular diet where I absolutely had to eat now or I'd feel rotten," she says. "I like this diet for that very reason."

Then there's Michael, who combined Dr. Atkins' New Diet Revolution (M. Evans & Co., Inc.) with an exercise program for two months and lost 30 pounds. He says the program made him realize how carbohydrate-heavy his diet was, and since losing the weight, he is now motivated to eat better. Even so, he's now abandoned the protein regimen. "I wasn't willing to commit to the fundamental lifestyle change the Atkins diet demands," he explains. "I love things like fruit too much. And I was craving carbs too much."

Millions of Americans have bought into these high-protein plans. In the wake of their popularity, however, people are confused about how much protein they really need. And many mainstream health and nutrition experts remain wary of these diets. They worry about the health hazards of eating a high-protein diet (which often translates into high-fat) for an extended period of time.

The body's building blocks

Protein is essential. There's no argument about that. It's what keeps our bodies going. Here's how it works: Amino acids are the building blocks of protein. There are 20 amino acids we need, 11 of which the body can make on its own. But the remaining nine we have to get from the foods we eat. Our bodies need protein to repair and maintain body tissues, produce hemoglobin to carry oxygen to the cells, and to produce antibodies, enzymes and hormones.

There are two types of protein — complete and in-complete. Complete proteins contain the nine essential amino acids the body cannot make. They include meat, poultry, chicken, fish, eggs, soy protein concentrate and dairy products.

Incomplete proteins, foods such as dried beans, nuts, bread, corn and rice, are missing one or more of the essential amino acids. However, you can help balance your diet by simply combining these foods together throughout your day, ending up with complete proteins.

Best-selling protein advice

Most professional health organizations, such as the American Heart Association and the American Cancer Society, recommend you eat 55 to 60 percent of your daily calories from carbohydrates, 10 to 15 percent from protein and 25 to 30 percent from fat.

But the authors of today's popular protein plans say that carbohydrate-laden pyramid is what's making us fat. Their theory is this: If you eat too many carbohydrates, your body produces too much insulin. And if you have too much insulin in your system, you will store more fat.

In February, two studies were released that showed the Atkins diet to be a safe and effective way to lose weight. Researchers at the Durham Veterans Affairs Medical Center in North Carolina found that average, mildly obese people who followed the diet lost about 21 pounds in four months and had positive changes in heart risk factors such as reduced LDL ("bad") cholesterol and increased HDL ("good") cholesterol. These results were supported by a second study from researchers at the Atkins Center for Complementary Medicine in New York City. Researchers plan to continue the study in order to monitor the long-term effects of the diet.

Therefore, researchers recommend a diet lower in carbohydrates and higher in protein and fat. These plans appeal to dieters not only because they promise quick weight loss but also because they allow us to eat practically all the red meat, eggs and cheese we want — foods we've been told to limit. Dieters also may find they're not as hungry when they eat more protein. That's because the body breaks it down more slowly than carbohydrates.

For the most part, people do at first lose weight quickly on these diets. But much of that initial weight loss is water, says Ruth Kava, nutrition director for the American Council on Science and Health. That's because carbohydrates are stored in our cells as glycogen, which is what our bodies use for quick energy. With every molecule of glycogen, our bodies also store a certain amount of water.

When you restrict carbohydrates, the body's store of glycogen and water are depleted, says Janis Jibrin, M.S., R.D., author of The Unofficial Guide to Dieting Safely (Macmillan USA). "With a 10-pound weight loss," she explains, "easily half of that could be water."

Decreasing the amount of carbohydrates we eat isn't a bad idea, says Lisa Hark, Ph.D., R.D., director of the Nutrition Education and Prevention Program at the University of Pennsylvania School of Medicine in Philadelphia. But increasing protein and fat isn't the sole answer.

According to the National Health and Nutrition Examination Surveys (American Journal of Clinical Nutrition, 1997, vol. 66), Americans today are eating 220 more calories a day than in 1970. Those extra calories are being consumed from carbohydrates. "Whole grains are obviously carbohydrates," says Hark. "But they're an excellent source of fiber and B vitamins, and cutting them out doesn't make sense. But cutting down on them does."

Diet as disease defense

Even before the low-carb, high-protein hype, Americans were eating more protein than necessary. In fact, the average American consumes 161 percent of the Recommended Dietary Allowance for protein each day, according to the most recent U.S. Department of Agriculture surveys.

More protein, in particular animal protein, often means more fat. And we know eating more fat, especially saturated fat, puts us at an increased risk for heart disease, says Kava. "We know that people who eat lots of fruits and vegetables tend to have lower incidences of cancer," she adds.

Some dieters may not feel good when they restrict carbohydrates. When your body doesn't get the glucose it needs from carbohydrates, it produces ketones from fat. Our brains don't run as efficiently on ketones as they do on glucose, so some people may feel dizzy or fatigued.

In addition, Cornell University researchers found that animals fed lower-protein diets voluntarily exercised more. And, humans and animals on lower-protein, lower-fat diets actually consume more calories in the form of carbohydrates but are less likely to convert the energy to body fat.

Yet some people believe we were meant to follow a high-protein, low-carbohydrate plan because, they say, that's how our prehistoric predecessors ate. While the two diets do have some characteristics in common, such as a low-carbohydrate content, they also vary in that today's diets typically include more fat, more dairy and less fruit than was eaten by people in the Stone Age, says Loren Cordain, Ph.D., a professor in the Department of Health and Exercise Science at Colorado State University in Ft. Collins, Colo.

Even the low-carb connection is skewed, says Cordain, because Stone Age inhabitants would have eaten unlimited fruits and vegetables, which are limited in today's high-protein plans. In addition, the main sources of protein in the Stone Age came from wild animals, which didn't have the same types of fat as in today's feed-lot cows and pigs, which likely contribute to the high rates of heart disease we see today, says Cordain.

People would benefit, adds Cordain, by eating more fruits and vegetables and cutting down on sugar and salt. In addition, he says the best sources of protein in today's diet are those that are lean, particularly seafood and fish.

The bottom line

Oftentimes, high-protein, low-carbohydrate diets appeal to people who want a quick fix. But a quick fix rarely leads to a lifelong weight-loss solution. "The problem with high-protein diets is they are not typically a way we can eat for the rest of our lives," says Kava. "One can get tired of even bacon and steak. A lack of variety of different types of food with different sensations or textures tends to get boring and we start to look for new and different tastes."

This is particularly true when you have to eliminate so many foods. Further, any diet that restricts certain foods sets you up to crave them. "I have talked to people who are on these diets, and they have dreams about bagels," says Jibrin.

Most experts agree that we do need to cut down on carbohydrates. But not because of the chemical reactions they cause in our bodies. It boils down to portion control, says Jibrin. "When you go to a restaurant, you get these huge portions of pasta," she says. "Bagels have tripled in size, cookies have quadrupled. It's not the carbohydrate's fault — it's the portion size."

Instead of upping your protein, make small changes step by step. "Eating the way the health authorities tell you to eat, with all those vegetables and whole grains, can be hard," says Jibrin. "You really have to not despair. If you can't live up to that ideal, just start looking at what you eat and work on changing a little at a time. If you eat one more vegetable a day, that's great. Instead of fries five days a week, have them three days. Keep working on the little, manageable changes until you're comfortable with them. Then move on to tackle the next issue."

Julie Stafford is a freelance health writer based in Niwot, Colo.
Illustration by Cyril Cabry