The diet wars.

It's spring, when a young (or not-so-young) person's fancy turns to ... bathing suits. It's one thing to put on a few extra pounds over the winter. It's quite another to share those pounds with the general public.

This hasn't been a blockbuster season for diet books. No one's come up with a brilliant new scheme (and publishers have to wait a decent interval before repackaging the old ones). Of course, diet books from previous years--like Dr. Atkins' New Diet Revolution, The Zone, and Dean Ornish's Eat More, Weigh Less--still do a brisk business. And millions of people still swear by whatever magic helped them shed those ten pounds (unless the pounds have returned).

But something has changed. Results from two not-yet-published studies may become big news. (With the dearth of good research on diets, any news is big news.)

In one study of obese people, those who were told to follow an Atkins diet lost more weight--and were more likely to stick to the diet--than those told to follow a lower-fat diet. (An Atkins diet is an all-you-can-eat buffet of red meat, cheese, eggs, butter, and other fatty protein foods but little or no carbohydrates.)

In the second study, overweight women who ate a very-low-fat vegan diet lost more weight than those who ate a typical lower-fat diet. (A vegan diet has no meat, poultry, seafood, eggs, or dairy foods. It's typically loaded with whole grains, beans, vegetables, and fruit--in other words, carbs.)

What's going on? Just another battle in the Diet Wars.

Atkins on Trial

"As a health professional, I was always being asked about the Atkins diet," says Gary Foster of the University of Pennsylvania. "Colleagues would tell me that they had patients who had lost weight on Atkins, but it was hard to recommend it knowing that a diet high in saturated fat can increase the risk of heart disease and cancer."

So Foster-and colleagues in Colorado and St. Louis randomly assigned 42 obese people to either an Atkins diet or a low-calorie, lower-fat, higher-carbohydrate diet. The researchers didn't feed the participants. They wanted to test the diets under real-life conditions.

After an initial visit with a dietitian, half of the dieters got a copy of Dr. Atkins' New Diet Revolution and half got a copy of a weight-loss manual that recommends a "conventional diet" that's low in calories and fat and high in carbohydrates.

So far, Foster has published only a brief summary of results from the first few months. (1) But the trends hadn't changed several months later.

"A third of those on the conventional diet--but only a tenth of those on the Atkins diet--dropped out," says Foster. And of those who remained, the Atkins group lost twice as much weight as the 3 other group.

"We were as surprised as anybody," says Foster. "I'm not ready to change our diet recommendations based on a study of 40 people. But the data are the data."

Does that mean we should all switch to an Atkins diet? Not quite.

Cholesterol Caveats

"I'd be very cautious about drawing conclusions because we're still looking at the weight-loss phase," says co-investigator James Hill of the University of Colorado. People lose weight on most diets.

"The Atkins diet may be a good way for some people to lose weight, because it may provide more satiety and people might like it better. The question is: Are they able to maintain the weight loss?"

Another concern: Does the Atkins diet boost blood cholesterol? In the first 12 weeks, LDL ("bad") cholesterol rose nine percent in the Atkins dieters and dropped 15 percent in those on the conventional diet. But over time, the difference in LDL between the two groups diminished.

What's more, any damage the Atkins dieters sustained from higher LDL might have been offset by a ten percent rise in their HDL ("good") cholesterol. But the key question is: What happens after they stop losing weight?

"Weight loss has such a powerful effect on both LDL and HDL cholesterol that it can overcome a detrimental effect of saturated fat," says Hill.

In other words, LDL may climb once people stop losing--and start trying to maintain--their weight.

That doesn't trouble some dieters. "People say, why not follow an Atkins diet and take a cholesterol-lowering statin drug like Lipitor?" says Foster. Over the long term, that's not a good strategy. Red meat is linked to a higher risk of prostate and colon cancer.

Of course, many people go on an Atkins diet for just a month or two. Would that raise the risk of those cancers? No one really knows.

Protein Possibilities

Atkins argues that cutting carbohydrates is the key to weight loss, because carbs raise insulin levels, and insulin is "the fat-producing hormone," which converts blood sugar into stored fat. Yet studies show that insulin doesn't affect weight loss. (2)

"All of Atkins's fancy hypotheses haven't been borne out in other research," says Foster. His hunch: People on the Atkins diet eat fewer calories.

"If you eat bacon and eggs instead of three jelly doughnuts for breakfast or skip your usual candy bar at 3 p.m., you've hit a home run on calories," he explains. "The universe is small when you can't eat carbs."

Another possibility: The extra protein in the Atkins diet may curb your appetite slightly. In 1999, Danish researchers allowed 65 healthy, overweight, or obese people to choose all their own food at a university grocery store (which monitored their purchases). (3) Those who were told to get 25 percent of their calories from protein lost more weight (20 pounds) than those who were told to get 12 percent of their calories from protein (11 pounds).

But, unlike Foster's study, the Danish experiment made sure that both diets got less than 30 percent of their calories from fat. So if protein helps--which is far from certain--you don't need the fatty foods in Atkins's menus to get it.

In fact, a new study turns Atkins on its head.

The Anti-Atkins Diet

An Atkins diet is essentially an animal-food diet. Ironically, this season's second new study features a diet that's made up entirely of plant foods.

Researchers randomly assigned 64 overweight postmenopausal women to either a typical American Heart Association lower-fat diet or a very-low-fat vegan diet.

"Both groups lost weight, even though we didn't instruct them to limit calories or portion sizes," says author Neal Barnard of the Physicians Committee for Responsible Medicine in Washington, D.C. That often happens when people join a study and are asked to record every morsel they ingest.

However, those on the vegan diet lost more weight (13 pounds) than the others (eight pounds) over the 14-week study, even though the vegan dieters ate less protein. (They reported eating only 44 grams of protein a day. That's slightly less than the government's Recommended Daily Allowance of 50 grams.)

"The women on the vegan diet lost weight without our telling them to limit calories, with no increase in hunger, and no change in exercise," says Barnard.

The vegan diet got only ten percent of its calories from fat. Like the diet recommended by physician and author Dean Ornish, it consists mostly of whole grains, fruits, vegetables, and beans, with little or no added fat (oils, nuts, seeds, peanut butter, or avocado).

"It's a high-carbohydrate diet, but the carbs are vegetables and brown rice and beans, not soda, french fries, ice cream, and candy bars," says Barnard.

However, Ornish allows some fat-free yogurt and skim milk, while Barnard allows only their soy versions. (Barnard's Physicians Committee for Responsible Medicine is an animal welfare organization that promotes a vegan lifestyle.)

What accounts for the success of the vegan diet?

"We think the diet works because eating very little fat cuts calories without people even knowing it," says Barnard.

But that may not be the whole story.

Diets with a Difference

Both the Atkins and Barnard diets require a major overhaul of your menu. On Atkins you lose everything from pasta and sandwiches to ice cream, cake, and cookies.

On Barnard you ax any food with even a hint of chicken, seafood, meat, eggs, or dairy, and you kiss goodbye your pizza, yogurt, (most) salad dressings, and even the little oil you use to saute your veggies. What's more, along with those foods goes just about anything you'd order in most restaurants.

"It's easier for people to make big changes than little ones," says Barnard.

But even less drastic changes may help dieters.

Last fall, a Harvard study pitted a typical low-calorie, low-fat diet against a low-calorie Mediterranean diet. (4) (Both were very low in meat, cheese, butter, and other saturated fats. But the Mediterranean diet had more unsaturated fats--from peanut butter, nuts, or olive or canola oil--and less pasta, bread, and other carbs.)

Sure enough, the Mediterranean-dieters were more likely to stick with it. And, excluding dropouts, they lost more weight (ten pounds) after 18 months than the low-fat group (six pounds). Why?

"The Mediterranean group didn't feel like they were dieting because they could eat foods they had avoided during the fat phobia of the 1980s and 1990s," notes co-author Katherine McManus of Brigham and Women's Hospital in Boston.

Low-fat diets worked like a charm when they first hit the scene, too. Maybe any diet is doomed to fail when it's no longer novel.

But the Mediterranean dieters had something else going for them. "They ate more vegetables because they were able to use full-fat salad dressings and saute the vegetables in a little oil and garlic," says McManus. The vegetables could have helped weight loss by making the diet less calorie-dense. And it's the vegetables--and so little saturated fat--that make the Mediterranean diet healthy.

Dieter's Dilemma

With no firm answers, dieters are stuck with common sense. And that should steer you away from Atkins.

Who needs hefty portions of red meat that may raise the risk of cancer? Why deprive yourself of the fruits and vegetables that could lower your risk of cancer, stroke, and heart disease?

"So far, we haven't done so well helping people lose weight, so we have to keep an open mind," says the University of Pennsylvania's Gary Foster. "But we have to be sure of the safety and effectiveness of a diet before we recommend it."

Your lifelong diet should lower your risk of heart disease, stroke, cancer, and diabetes (see "Lean for Life"). If you want to lose weight over the short term, here are some things to keep in mind:

* Shoot for eight to ten servings of fruits and vegetables a day. Also, take a multivitamin-and-mineral supplement and extra calcium to replace what your pared-down diet might be missing.

* If you find it easy to cut (almost) all carbs, try The Zone's advice: Start with a palm-size serving of low-fat protein (like chicken or fish), and fill up the rest of the plate with fruits and vegetables, plus a small amount of oil (to saute vegetables, dress salads, etc.).

* If you find it easy to cut (almost) all fat, try one of Dean Ornish's books or Barnard's Turn Off the Fat Genes (Harmony, 2001).

(1) Obesity Research 9 (suppl 3): 85S, 2001.

(2) Metabolism 50: 795, 2001.

(3) Int. J. Obesity Rel. Metab. Disord. 23: 528, 1999.

(4) Int. J. Obesity Rel. Metab. Disord. 25: 1503, 2001.

RELATED ARTICLE: Lean for life.

This diet may not lead to dramatic weight loss--it doesn't wipe out all carbs, fats, animal foods, or anything else--but it should help you shed pounds and lower your risk of heart attack, stroke, diabetes, and cancer.

It's similar to the DASH diet (see Dec. 2000, cover story), but it emphasizes whole grains and can be adapted for vegetarians. It's got 2,000 calories--little enough for some people to lose weight--but you can cut it by roughly 100 calories for every serving of snacks, grains, fats, or beans you skip (dropping 1/3 cup of nuts cuts 250 calories).

Just watch those serving sizes! A "serving" of pasta is half a cup--not the 3 1/2 cups served in a typical restaurant portion of spaghetti. And a serving of grains is one ounce; that's a slice of bread, not the four ounces you'd get in a typical bagel.

Food & Servings       Examples of 1 Serving

Grains                1 slice whole-grain bread
7 to 8 a day          1/2 cup whole-grain cereal

Vegetables            1 cup raw leafy vegetables
4 to 5 a day          1/2 cup raw non-leafy vegetables
                      1/2 cup cooked vegetables

Fruits                1 piece of fruit
4 to 5 a day          1/2 cup fresh, frozen, or canned fruit

Low-fat Dairy         1 cup fat-free or 1% milk
2 to 3 a day          1 cup low-fat yogurt
                      1 oz. fat-free or low-fat cheese

Seafood & Poultry     3 oz. broiled or roasted seafood
2 or less a day         or skinless poultry
                      1 soy veggieburger

Nuts & Beans          1/2 cup cooked beans
4 to 5 a week         1/3 cup nuts

Added Fats, Oils, &   1 tsp. oil or tub margarine
Salad Dressings       1 Tbs. low-fat mayonnaise
2 to 3 a day          1 Tbs. regular salad dressing
                      2 Tbs. light salad dressing

Snacks & Sweets       1 piece of fruit
5 a week              1 cup low-fat yogurt
                      1/2 cup low-fat frozen yogurt