Losing it: does Atkins trump other diets?

Here's the latest flab report: Two out of three American adults are now overweight. Roughly 45 percent of women and 30 percent of men say they are trying to slim down. (Have the others given up?) Yet we still don't know which diet can help you kiss those extra pounds goodbye. Should people bother counting calories or should they just count carbohydrates?

Last spring, researchers announced the results of three well-designed studies. They're the first of several trials that pit an Atkins (low-carb, high-fat) diet against a conventional (lower-calorie) diet. Here's the latest from the front (and rear) in the diet wars.

NO FLASH IN THE PAN

"I was very surprised by our results," says Gary Foster, the University of Pennsylvania School of Medicine researcher who led one of the new studies. "I thought that the people on the Atkins diet would have lost more weight and gained it all back."

Foster's team had randomly assigned 63 obese men and women--their average weight was about 215 pounds--to one of two diets(1):

* The Atkins group got a copy of Dr. Atkins" New Diet Revolution, which urges dieters to cut carbohydrates to 20 grams a day and then gradually increase them to 40 to 60 grams (for the average person). It sets no limits on calories of fat.

* The conventional diet group got a copy of The LEARN Program for Weight Management, which recommends cutting calories (down to 1,200 to 1,500 a day for women and 1,500 to 1,800 a day for men), but not carbs in particular. LEARN recommends no more than 25 percent of calories from fat. That's less than the average American eats (34 percent), but it's nowhere near a very low-fat diet like Dean Ornish's (10 percent of calories from fat).

"I expected the Atkins group to lose more weight because the diet is more structured and it causes water loss," explains Foster. "I also thought the fervor in Atkins's book would make them more zealous about the diet than the LEARN manual."

In fact, the Atkins dieters lost an average of about 15 pounds after six months--significantly more than the seven pounds lost by the LEARN dieters. But after a year, the Atkins group had regained six pounds, while the LEARN group had regained two pounds. That made the difference between the two groups no longer statistically significant.

"At least the Atkins dieters didn't gain it all back," says Foster. "I predicted a quick flash in the pan."

Were the Atkins dieters disappointed to lose only nine pounds after a year? After all, the book suggests that dieters are likely to lose 10 pounds per month.

"We didn't formally assess whether they were happy," says Foster. "But they were about 60 pounds overweight on average when they entered the study, so I suspect that there was a discrepancy between what they wanted to lose and what they lost."

DROPOUTS

Of course, some of the Atkins dieters lost more than nine pounds in the first year. In fact, that average includes dieters who dropped out of the study--40 percent of the original 63 participants. (If it didn't include them, the researchers wouldn't have known if something about the dropouts had biased the results.)

"People forget that this was only a pilot study," says Foster. "We're now starting a larger study on 360 people." In the full study, participants will meet more often, "so we expect better adherence."

In the second new study, Frederick Samaha and colleagues at the Philadelphia Veterans Affairs Medical Center told 132 severely obese people--they averaged 288 pounds--to eat either a low-carb diet (30 grams a day) or a diet with 500 fewer calories(2), After six months, the low-carb dieters lost an average of 12 pounds while the lower-calorie group lost four pounds.

In the third study, Bonnie Brehm and co-workers at the University of Cincinnati put 53 obese women on either an Atkins diet or a diet that cut about 4S0 calories a day(3). After six months, the Atkins dieters lost 19 pounds, while the lower-calorie group lost nine pounds.

Those studies lasted only six months, so the difference between groups might have faded over time, But the results do raise the question: Why might a low-carb diet work?

THE MONOTONY DIET?

According to Dr. Atkins" New Diet Revolution, a low-carb diet works because it causes people to burn fat, which dispatches appetite-suppressing ketones into the blood. But Foster's

study found no link between weight and ketones.

Calories did matter, however. In the VA study, the low-carb group are 460 fewer calories a day. The lower-calorie group cut only 270 calories (despite being told to cut 500).

"It's intriguing that people lose more weight when we tell them to cut carbs," says Foster. "When we don't tell them to cut calories, they cut more calories. That's potentially exciting."

Maybe it helps dieters to eliminate whole categories of food (bread, pasta, rice, potatoes, cereals, and sweets in the case of Atkins). Or maybe a low-carb diet works because the fat makes people feel full longer or because it limits variety.

"My guess is that when you tell people that they can eat as much as they want, at first they eat a lot, like binge eaters," says Foster. "But after a while boredom sets in and a pound of bacon isn't what it's cracked up to be."

In other words, monotony may be the dieter's friend. "After some break point, people may go off the diet because it's so monotonous," suggests Foster. "But until then, it may help."

SAFETY FIRST

The Atkins dieters' weight loss wasn't the only thing that surprised Foster. "We expected that the saturated fat in the Atkins diet would raise LDL," he says.

"But we saw only a transient effect at three months, and by six and 12 months, the increase disappeared."

While LDL ("bad") cholesterol declined in the conventional dieters, it didn't fall much, probably because that group didn't lose much weight.

"People have to lose about ten percent of their body weight to lower LDL," says Robert Eckel, professor of medicine at the University of Colorado and president of the American Heart Association's Council on Nutrition, Physical Activity and Metabolism. "A lot of doctors are misled about that."

Why didn't LDL rise in the Atkins group?

"Weight loss may counteract the effect of saturated fat," says Foster. "Even after the Atkins group stopped losing weight, they were still eating fewer calories to maintain their lower body weight." That could have been enough to keep their LDL from rising.

It isn't what the scale Shows after three or six months, but whether the diet will reduce the risk of disease.

In fact, the most compelling change wasn't in LDL, but in triglycerides, which also raise the risk of heart disease. While triglycerides didn't rise of fall on the lower-calorie diet, they plummeted 28 percent on the low-carb diet.

"The magnitude of the rail in triglycerides was remarkable," says Foster. "It's comparable to what you'd get with drugs."

Does that mean the Atkins diet is safe?

"Any recommendations based on this study are premature," says Foster. "Don't forget--we had only 37 subjects at the end of one year." (And only 20 of the 37 were on the low-carb diet.)

Like Foster, most researchers aren't ready to give the Atkins diet a clean bill of heart health based on LDL alone.

Do meals that are loaded with saturated fat cause damage by temporarily flooding the bloodstream with artery clogging fats? Do they make the lining of artery walls more prone to cholesterol deposits? Do platefuls of meat, cheese, and cream offer less protection against heart attacks and strokes because they lack fruits, vegetables, seafood, beans, and whole grains? There's evidence for each possibility.

"LDL isn't adequate to address the heart attack issue," says Eckel. "Plenty of heart attacks occur in people with normal cholesterol."

Other potential problems: Animal fats account for 90 percent of our exposure to dioxin, a known human carcinogen. What's more, "a high-protein diet could accelerate kidney failure or harm people with early liver disease," Eckel explains. "And they may not know they have it."

High-protein diets may also cause the body to excrete more calcium in the urine. "It may be a transient effect, but I wonder if it could change bone density over time," says Eckel.

THE LONG HAUL 

Over time is the key. Don't confuse the two debates: One is what diet leads to quick weight loss. The second is what's healthy for the rest of your life.

"It's okay if people just follow Atkins for three to six months to get into their high school graduation dress," says Eckel. "The bottom line isn't what the scale shows after three or six months, but whether the diet will reduce the risk of heart disease, stroke, diabetes, cancel and other outcomes of obesity."

Foster's new study should begin to answer some of those questions. "It's designed to look at bone density, body composition, endocrine function, kidney function, and exercise tolerance," he notes. All are safety issues raised in earlier studies of the Atkins diet. And it will look more closely not just at levels, but at the type of LDL, HDL, and triglycerides. "It's a comprehensive safety and efficacy trial," he says.

Yet even the new study won't be able to say whether the meat-heavy Atkins diet raises the risk of prostate and colon cancer, Foster acknowledges. "That's a third or fourth generation study. It would take more money, more power, and more screening."

So what should overweight people do in the meantime?

DIET ABCs

"I still recommend a diet like the one used in the Diabetes Prevention Program," says Foster. In that study, people who exercised and lost weight--an average of 12 pounds--by cutting fat and calories cut their risk of diabetes by 60 percent over four years.(4)

"Even though exercise was part of the program, it's still convincing because more than 3,000 people followed the diet for four years," he explains.

But a low-carb diet might still make sense for some dieters. "Even though it's premature to recommend a low-carb diet for widespread adoption," says Foster, "a physician might still decide that it's right for an individual."

The physician could monitor the patient's cholesterol, bone density, and kidneys. And the dieter could go heavy on chicken and fish instead of red meat.

Eventually, researchers may know which diet works best for which people. "In ten years, we may have enough data to know who will do better on one diet than another," says Foster. "We won't ask, 'Which diet wins?' but, 'When do we recommend diet A and when do we recommend diet B?'"

THE BOTTOM LINE

* A low-carbohydrate diet may lead to quicker weight loss than a diet designed to cut calories, but don't expect to lose as much as diet books claim. What's more, the low-carb diet may not lead to greater weight loss after the first six months.

* The long-term effect of a low-carbohydrate diet on the risk of heart disease, stroke, cancer, and osteoporosis has not been tested.

* If you try a low-carb diet, consider a healthier version like the one recommended by Barry Sears, author of The Zone: Start with a palm-sized serving of low-fat protein (like poultry, seafood, or soy) and fill up the rest of the plate with fruits and vegetables plus a small amount of nuts, avocado, or oil (to saute vegetables, dress salads, etc.).

* Decades of research suggests that a lifelong healthy diet is rich in fruits, vegetables, beans, whole grains, seafood, poultry, and low-fat dairy foods, as well as some oils, nuts, and other unsaturated fats.

(1) New Eng..J. Med. 348: 2082, 2136, 2003.

(2) New Eng, J. Med. 348: 2074, 2003.

(3) J. Clin, Endocrin. Metab, 88: 1617, 2003.

(4) New Eng. J. Med. 346: 393, 2002.