It's Not the Carbs, It's the Calories

Fats aren't the only bad boys on your daily menu. Carbohydrates are also suspect, depending on what type you pile on your plate.

Those who are anti-carb point to two studies in the New England Journal of Medicine showing that obese patients on a high-protein, high-fat, low-carb diet lost more weight in the first six months and scored better on some heart-health tests than obese patients on traditional low-fat diets. Those studies appeared in 2003.

At one year, however, the amount of weight lost was not significantly different between the two groups. The researchers also expressed concern about the high-protein diet in the long term, because of its possible effect on the kidneys and other body functions.

Low-carb products flooded the market as a consequence of those studies. You can find them on cable shopping networks, in restaurants, and at low-carb superstores. Even chocolate has gotten a low-carb makeover.

So if you're a steak-and-potatoes kind of guy, should you just skip the potato and pile on more red meat?

Not so fast. A 2002 report on healthy eating by the National Academy of Science's Institute of Medicine (IOM) recommends that adults get 45 to 65 percent of their calories from carbohydrates. That's in line with the 50 to 55 percent most of us eat now, says Joanne R. Lupton, Ph.D., who chaired the IOM panel that wrote the report. Thirty percent of daily calories should come from fat, with less than 10 percent from saturated fat, and 10 to 35 percent should come from protein.

So while you might need to rethink the nutritional qualities of the carbohydrates you eat, experts say you still need your carbs.

Brain food

Glucose, a simple sugar that comes from carbohydrates, is fuel for your brain. To keep thinking straight, the IOM says, children and adults should eat at least 130 grams (520 calories) of carbohydrates a day. Many low-carb diets call for no more than 20 to 30 grams of carbohydrates each day.

What can go wrong if you don't get enough carbs? "'Hitting the wall' is an athlete's term for what happens when you've run out of all the carbohydrates [glycogen] you've stored in your muscles and liver," says Althea Zanecosky, R.D., an American Dietetic Association (ADA) spokeswoman and former marathon runner. "When athletes reach that point, you see them staggering. It's really hard, not just physically, but hard mentally to focus."

When the body runs out of carbohydrates for fuel, it can't break down fat properly. This causes a condition called ketosis, because of the accumulation of ketones (carbon fragments) created by the incomplete breakdown of fats. Although you feel less hungry when your body is burning fat, ketosis can lead to health problems.

High-protein diets can increase the risk of developing:

• Kidney problems, because consuming excess protein taxes the kidneys.

• High blood cholesterol, because these diets include red meat and whole dairy products, both of which are high in saturated fat. High cholesterol can increase your risk for heart disease and some types of cancer. Although the NEJM studies found that the low-carb dieters wound up with lower triglycerides (blood fats) and higher HDL ("good") cholesterol, those results were for the short term.

• Osteoporosis, because the excess protein makes the body excrete more calcium. This also can cause kidney stones.

• Cancer, because a person on a high-protein, low-carb diet misses out on the protective vitamins, minerals, and antioxidants found in fruits and vegetables.

So, what's behind the low-carb diet hoopla? In the two NEJM studies, dieters using the low-carb, high-protein plan of the late Robert Atkins, M.D., lost more weight—at least at first—than obese patients on traditional low-fat, high-carb diets. Why? Much of the weight loss could be attributed to a loss of water weight. And the monotony of Atkins-type diets that limit food variety often causes people to eat less.

But some experts weren't impressed with the Atkins dieters' weight loss. And by the end of the studies—one lasted six months, another a year—many patients in all groups had failed to stick with their diets. Of those who had, many had regained their weight or added even more. There were no major differences between the low-carb and high-carb groups.

The bottom line

If you want to lose weight, you need to reduce the number of calories you consume. To do this, most doctors still back low-fat diets. Not even the lead researcher in the year-long Atkins study—Gary Foster, Ph.D., a weight loss expert in Philadelphia—recommends low-carb diets to his patients.

Dr. Foster thinks such diets might have potential for some folks. But we know too little about their effectiveness, safety, and long-term health impact, he says. Of the 63 patients who started his study, only 37 finished. The dropout rate was similar for each of the two diets.

Dr. Foster has launched a much larger five-year study. He wants to know how low-carb diets affect arteries, hearts, kidneys, bones, and exercise ability. He also wonders, "Can people stick to such a diet for two years?" That's the minimum for successful weight loss schemes.

Still, we've learned a few things. Cutting carbs can cut calories. And healthy amounts of "good" fats—polyunsaturated and monounsaturated fats in sources like olive oil, fish oils, and nuts, as opposed to saturated fats in red meats and full-fat dairy products—are good for you.

"If you consume reasonable portions of [lean] protein and healthy fats, such as olive oil instead of butter, you'll feel more satisfied and less likely to get really hungry and overeat," says Jo Ann Carson, Ph.D., R.D., a nutrition researcher in Dallas.

Carb concepts

• Choose nutrient-packed carbohydrates. Johanna Burani, R.D., co-author of Good Carbs, Bad Carbs, says carbohydrate-rich fruits, vegetables, legumes, and whole grains deliver vital nutrients, vitamins, and minerals. The list includes fiber, calcium, iron, and anti-oxidants. That's also true of 1 percent dairy foods.

• Choose whole grains. Compared with refined grains such as white bread, whole grain products are more nutrient dense—they provide more fiber, vitamins, minerals, and health-promoting phytochemicals. Because they contain fiber, whole grains are less energy dense—they provide fewer calories per amount of food—and so help you feel full longer on fewer calories.

• Avoid nutritionally empty carbs. Foods such as sodas, fruit punches, juices, cookies, cakes, and pastries are mostly pure sugar and/or also have a lot of fat in them. If you avoid such foods, you get rid of excess carbs, as well as the fats that tag along with them.

• Cut back on added sugars. These are added in the making of such foods as candy, soft drinks, fruit drinks, and pastries. Many nutrition experts recommend that sugar contribute no more than 10 percent of your total calories. Sugar-laden foods displace healthy foods and contribute to consumption of excess calories.

• Limit portion sizes. Don't "supersize" meals. Twice the fries and twice the soda for 29 cents more might seem like a good deal, says Dr. Lupton. But it's not a good investment in your future health.

• Get moving. "It's a question of energy in [calories] and energy out [exercise]," says Dr. Foster. In the long run, "you have to decrease your calories and increase your physical activity level."

Can a pill make you shed pounds?

The concept sounds great: Take one of the heavily promoted carbohydrate blocker pills—an extract made from white kidney beans—and the carbs you eat never reach your bloodstream as sugar.

Carb blockers don't block all carbohydrates. They hamper the enzyme that breaks down complex carbohydrates, or starches, into glucose molecules. And Jana Klauer, M.D., an obesity researcher in New York City, says they only block some complex carbohydrates, not all of them.

Dr. Klauer thinks the concept has the potential to help very obese people. But even though many Americans are taking the pills, she doesn't recommend them. No significant studies have proven that they work, she says.

"I think it's an artificial way of eating," she says. "One of the packages says, 'Eat all the pasta and bread you want without gaining weight.' That's just wrong. The purpose of eating is to nourish your body with needed nutrients."

The most common side effect, experts say, is gas and bloating. That's similar to lactose intolerance, which results from an enzyme's failure to break down lactose, a natural sugar. Carb blockers work much the same way.

"Why would anyone intentionally inflict that on themselves as a way to lose weight?" asks dietitian Zanecosky. Her advice: If you want to keep carbs out of your blood, don't put them in your mouth.