Americans, who have been receiving lots of press as the planet's fattest people, seem willing to try anything when it comes to losing weight. The American Dietetic Association (ADA), a Chicago-based organization of some 70,000 food and nutrition professionals, says our appetites now fuel a $30-billion industry of weight-loss products and programs. And none of them has been receiving as much attention lately as the high-protein, low-carbohydrate regimen that's the basis for such popular diets as the Atkins or the Zone.

Jim Ramer, a commercial production assistant in Sarasota, recently tried the Atkins diet; he says in two and a half weeks, 14 pounds melted off his body like the butter he was eating every day. Sarasota marketing rep Kathy Bell lost 10 pounds in just a few weeks by following the same routine.

"The Atkins diet and the Zone have been getting a lot of attention because they refute the former diets that support a low-fat, moderate-high carbohydrate diet," says Grace Lee, a registered dietictan at Doctors Hospital here in Sarasota. "Even more so, they permit dieters to eat foods high in fat, like bacon, sausage, cheese, meat, eggs and ribs, which is very enticing."

This is in sharp contrast to the Food and Drug Administration's official food "pyramid," which suggests that the average diet consist of 65 percent carbohydrates, 15 percent fat and 20 percent protein. But many critics say that with obesity bloating to epidemic proportions, Americans need to reconsider those proportions, particularly the recommended percentage of carbohydrates. Since the human body gets its fuel from only two places-fat stores and glucose-proponents of low carbohydrate diets argue that by restricting carbohydrates (which break down into glucose), you're removing one of those sources. This forces your body into a state called "ketosis" where it will burn fat instead.

During the initial "induction" phase of Atkins, carbohydrates are limited to 20 grams a day (an amount you can rack up in one peanut butter cup, a six-inch banana, or half a medium-sized bagel). After that, they are restricted to no more than 60. This is substantially below the recommended dietary allowance of 130 grams a day, and light years behind a man's average daily intake of 200 to 330 and woman's 180 to 230.

According to the Atkins Web site, if you're trying to lose a great deal of weight, you can continue this "induction" phase for six months or more, but Laura McLeroy, a registered dietitian for Sarasota Memorial Hospital, doesn't suggest that. She says such an abrupt and drastic decline in carbohydrates burns more than fat. "Ketosis tends to burn out the kidneys," she says-something Atkins continues to deny. "The kidneys filter products out of the body, and if they're forced to filter excess fats and proteins, it can be damaging over the long term." And despite what their literature says, McLeroy insists that, "Ketosis does burn muscle."

Not true, says Colette Heimowitz, director of education and research for Atkins. "Only when your body is not getting enough protein will it go to muscle," she says. "The Atkins protocol projects 30-to 35-percent protein, and if you're getting enough calories from protein and fat, your body will not burn muscle in ketosis."

Another thing McLeroy doesn't like about Atkins and other low-carb diets is that they tend to exclude fruit and vegetables, which are great sources of the vitamins, minerals and antioxidants we need to stay healthy.

"I missed fruit the most," says Bell, who tried the diet a second time to lose eight more pounds. She finally stopped after it left her too weak to complete her daily exercise regimen. "No matter what the books say, and I've read all of them, I followed the program exactly and was still too tired," she says.

Low-carb diets are also expensive, says Ramer. Because Atkins in particular requires substantial amounts of protein, Ramer says he was spending a lot more at the grocery store for steaks and meat. "It's too much meat," says Bell, who is now following a traditional low-calorie diet.

What people considering a low-carb diet need to know, says McLeroy, is that there are two kinds of carbohydrates: simple and complex. Humans do tend to digest "simple" carbs, like fruits and starches that contain sugar, much faster than we do "complex" carbs like whole grains and beans, that contain more fiber. And faster digestion of simple sugars does stimulate higher insulin production, something the Zone and Atkins proponents say can cause mood swings and weight gain.

Lee and McLeroy warn against avoiding all carbohydrates, because high-fiber vegetables, such as lettuce and broccoli (yes, these vegetables do contain carbohydrates) have more fiber, vitamins and nutrients, and are associated with lower rates of hypertension, cancer, arthritis and diabetes. Low-fiber carbohydrates like bananas are high in potassium, and tomatoes are rich in vitamins and linked to the prevention of prostate cancer.

A more sensible approach, says Lee, is to monitor the types of carbohydrates you eat.

To further complicate the issue, individuals process the same carbohydrates differently. "Some people break down the glucose created by a potato faster than they do pure sugar," says McLeroy. "You can control what you eat, but you can't control what your body's going to do with it. I may eat a baked potato and nothing happens; you may eat one and your blood sugar will skyrocket."

Even so, she says, "I tell all my clients that at the end of the day, a carbohydrate is a carbohydrate." After digestion, both kinds are absorbed into the body as glucose. The trick is to eat foods (like high-fiber complex carbohydrates) that release insulin at a more moderate pace.

Most nutritionists agree that carbohydrates themselves are not the problem as much as refined starches like pasta, white bread, crackers, white rice and corn flakes. Replacing carbohydrates with large amounts of fats and proteins is a dangerous recipe for raising your risk of heart disease and several types of cancer. Plus, both the Atkins and Zone diets encourage the use of supplements, and even sell them on their Web sites. The ADA's official stance is that any diet that requires supplements is by definition unbalanced.

McLeroy believes that diets like Atkins can work. "But only in the short term," she says. "If you have more than 10 pounds to lose, it's probably not a good idea."

Lee is not as generous. "Any diet that eliminates or drastically reduces entire macronutrients or multiple food groups.cannot be considered safe for the long-run or even the short-term," she says. "These diets, along with 90 percent of the diets, do not work. In fact, they can do more harm and lead to yo-yo weight loss and gain."

Ramer can attest to that. After religious adherence to 21 grams of carbs a day, his weight loss ended after two and a half weeks with a big, fat submarine sandwich. "Screw this," Ramer remembers saying. "I want the sandwich." And how long did it take him to gain back those 14 pounds? "I put it all on quite quickly after I went off the diet," he says.

"Well, of course, you're going to put it back on after you stop the diet," counters Atkins' Heimowitz. "If you go from 20 carbs a day back to 150, you will definitely gain weight back again." She adds, "Dr. Atkins never intended for people to give up carbohydrates entirely. That's a misconception and does a disservice to the entire program."

Atkins sources admit its eating plan has consequences. The Web site warns dieters about dramatic diuretic effects, dangerously low blood sugar levels in diabetics who are taking medication, and possible overdoses in people who are taking medicine to control their blood pressure.

"It is a diet that I would not recommend to anyone, no exceptions," says Lee. The Zone diet, however, is a different matter. While she declines to promote it, Lee says the Zone is more balanced because it does not have as great a proportion of calories coming from protein and fat. It also encourages exercise and the consumption of monounsaturated fats, the healthiest form for humans.

McLeroy says the Zone, with its emphasis on exact ratios of 40 percent carbohydrates, 30 percent protein and 30 percent fat, is very popular with her eating disorder patients. (The Zone advocates lean protein and natural carbohydrates like fruits and fiber-rich vegetables.)

And even the Institute of Medicine (IOM), a branch of the National Academy of Science, is rethinking our intake of carbs. Last September, the IOM issued a new dietary report that increases the recommended daily levels of fat and protein and reduces carbohydrates to those very near the Zone. It's also promoting the idea that people should be eating appropriately for their lifestyle.

"Weight loss is very specific," says McLeroy. "Sometimes people are eating great, they just need to watch their portions or exercise."

"Marathon runners have a much higher proportion of muscle to fat," adds Lee. "These runners are calorie-burning furnaces. As a result, they can eat many more calories than the same individual who has a high body-fat content, even though they may be the same weight."

Lee says any excess calorie that cannot be expended is stored as fat. "Any diet, if it is lower in calories than what one can burn off, will make you lose weight, whether that calorie is from fat, protein or carbohydrate."

And ultimately, says McLeroy, "The slower you lose weight, the more likely you are to keep it off," she says.

But to the normally 185-pound (five-foot, eight-inch) Ramer, the lure of instant gratification is just too tempting. He admits he went back on the diet in January to drop more weight for his April wedding.

A Grain of Truth

The trick to eating carbohydrates and avoiding weight gain is choosing the right kind.

If you're confused about how to tell a good grain from a bad, just remember one word: whole. Whole grains have not been milled, so they retain the bran and germ that are rich in fiber, B-vitamins and minerals. Products made with whole wheat taste better and are more filling.

And don't be fooled by labels. Breads often list "wheat flour," "unbalanced wheat" and "stoned wheat" in their ingredients. They're healthier if they've been made with "whole grain" or "whole wheat."

Some examples of whole wheat products are: brown rice, corn (despite what the low-carbohydrate crowd claims), whole oats, buckwheat and millet.

For a complete nutritional breakdown of every food, head to the USDA Web site http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl.

The Asian Model

Lowering carbohydrate intake is earning respect in scientific circles. Researchers from Cornell and Harvard University, along with the Oldways Preservation and Exchange Trust, a non-profit think tank, devised an eating plan based entirely on the Asian food model.

These Asian-influenced diets embrace rice products, noodles, breads and whole grains, fruits, vegetables, legumes (beans), nuts and seeds. They also recommend physical activity, plant-based fluids, like tea, even sake, beer and wine. They recommend small daily servings of low-fat dairy products and red meat once a month. These diets distinguish between animal and plant protein and fats and oils that the FDA food pyramid lumps together, even though nutritionists agree that protein in plants is different from that in animals, and that some fat is healthy and necessary.

Lee explains: "Western diets tend to be high in meat, dairy and fat. Asian diets tend to be high in vegetables, grains, soy, fish, and low in meat, dairy and high-fat desserts such as pastries, pies and cookies. Meat in Asian diets is used more as a side, not a main entrée. Rarely do you find a big 16-ounce steak on the dinner plate of an Asian consumer in their country." (However, when Asian societies adopt Western eating habits, they're also inheriting Western disease and weight gain.)