SHAPE UP
Understanding the effects of carbohydrates

By Charles Stuart Platkin

I'm amazed at the anger and frustration that Americans have toward carbohydrates. Perhaps they feel duped by nutrition experts for telling them to replace fat with an abundance of carbs, a recommendation that may be one of the causes for the recent increase in inches to our waistlines.

So, if carbs are so bad, then why were we told to eat more in the first place? And how can we tell the "good" from the "bad?"

Good vs. bad

A bottle of soda may have more calories than a carrot, but the carrot has a higher glycemic index. A number of variables affect the way your body handles carbs.

The idea was that smaller, simple sugars digest quickly, and the longer-chain complex carbs take longer to digest and therefore keep you full. But a complex carb can be refined (e.g., white bread, white rice), stripping away the good stuff such as fiber, vitamins and minerals. And some simple carbs are unrefined (e.g., fruits and vegetables) and still have fiber, vitamins and minerals. This was too simplistic for picking the right foods.

Then came the glycemic index (GI), which was created to determine the actual effect carbs have on blood sugar.

Foods with a high GI value raise the body's blood sugar levels very quickly, which signals the rapid release of insulin into the bloodstream; this rush of insulin then drops blood sugar levels. "This creates a slower and more difficult transition from the fasted to fed state — and studies have shown that this causes hunger," says Dr. David Ludwig, director of the Obesity Center at Boston Children's Hospital and Harvard Medical School.

In contrast, low GI meals cause a slower release of sugars into the bloodstream. And a steady, moderate insulin release allows for slower metabolism of carbohydrates.

Controversy over GI

"There aren't any conclusive studies. The majority of, but not all, one-day studies show low GI foods suppress hunger, but no relevant long-term studies have been completed," says Christine Pelkman, a professor of nutrition at the University at Buffalo. And "there's no proof that following a low GI diet will aid in weight loss," she said.

Another problem is that there are a multitude of variables — including fiber or fat content, acidity, food combinations, preparation method and even ripeness — that affect the way your body handles carbs.

Also, the index is based on a 50-gram carbohydrate portion of food. This is nowhere near the size of a typical serving of many foods. For example, carrots have a high GI (92); a 50-gram portion would be about 1 1/2 pounds.

To take the serving size into account, the glycemic load (GL) was introduced in 1997. The GL of a food is equal to that food's GI value multiplied by the number of carbohydrate grams in the portion of food, divided by 100. For example, the previously mentioned carrots with the high GI take on a GL of between 3 and 4, once portion size is taken into account. (For GI/GL values: www.glycemicindex.com.)

Still not perfect

GI and GL fail to account for calories. Take ice cream for example — a half cup has a GI of 42 and a GL of 7, making it seem almost healthy, but it's loaded with calories and fat. "If you look at GI/GL all on its own, it might not lead to a healthier or more satisfying diet," says Pelkman. In her study, she found no difference in hunger levels between participants fed a high GI and GL diet for six weeks. "Soda has a lower GI than carrots, so if you were just using GI, you would choose soda over carrots — these are not choices that would lead to weight loss," says Pelkman.

What should you eat?

Most nutrition experts advise eating a diet rich in whole grains, vegetables and fruit. But if you look at foods such as whole-wheat bread compared to white bread, they are both high glycemic foods.

Eating whole grains and fiber doesn't ensure a low GI, nor does it keep you from getting hungry. Research shows that foods high in fiber promote weight loss, NOT the fiber itself. Foods high in fiber also tend to be bulky foods that have lower calorie densities. "You need to look for low-energy, low-density foods that will satisfy you," says Pelkman.

Keep in mind: It's not just the GI that defines a "good" or "bad" carb. Good carbs also carry other nutrients or phytochemicals, have lower total calorie content, and are eaten with other nutrient-dense, low-energy foods.

Charles Stuart Platkin is a syndicated health, nutrition and fitness writer.