Joe Mullich
Freelance Health Writer
818-907-9109
Health Magazine
Moreover, nutrition expert say the index is too simple to accurately assess the way your body deals with real meals. For instance, a food's GI can change during cooking: If you boil instant rice for one minute, the GI rating is 65; boil it for six minutes, and the number nearly doubles.
Uncertainty about the ways foods interact raises more questions. David L. Katz, M.D., author of The Right Way to Eat and head of the Yale School of Medicine Prevention Research Center, cites a 1999 study involving 10 adults. It suggested that a high-fiber breakfast dampens the negative effects of a high-GI lunch on blood sugar hours later. Soluble fiber creates a physical barrier that slows the rate at which glucose and fat move from the intestines into the bloodstream. The implication: How bad a high-GI meal turns out to be depends on the dietary company it keeps.
The same holds true for single foods. "What if I put peanut butter on a banana?" asks Jackie Berning, Ph.D., an ADA spokeswoman. "I get an entirely different GI number than for each food individually. So unless I'm eating single foods in a fasting state, the numbers mean nothing."
What does Agatston think of the criticism? "It's a bit nitpicky," he says.
Agatston is not a nutritionist by training. In medical circles, his claim to fame is the Agatston Score, which helps predict heart attack and stroke risk by quantifying calcium buildup in the arteries. To help his patients improve their heart health, he began to study nutrition in the 1990s. Dissatisfied with the low-fat approach advocated by the American Heart Association, he started focusing on insulin (and insulin resistance) after having reviewed vast amounts of research. Using the glycemic index, he concluded, is the key to improving blood chemistry.
Agatston notes a small 1999 study conducted by David Ludwig, M.D., an endocrinologist at Children’s Hospital Boston and an assistant professor at Harvard Medical School. Twelve overweight teenagers who ate a high-GI breakfast went on to consume 80 percent more calories over the next five hours than when they ate a low-GI breakfast. In other words, the high-glycemic meal seemed to make the teens hungrier. In the 2002JAMA article that brought new attention to the GI, Ludwig concedes that there is no long-term data on the glycemic index and weight control. But he points out that 15 of 16 one-day studies show people were less satiated-and ended up eating more-following meals filled with high-GI foods versus meals containing low-GI ones.
Along with research, Agatston cites anecdotal evidence. Lots of people, he says, have gone on his diet and lost 30-plus pounds or dropped three dress sizes.
He has plenty of institutional support for his belief in the GI. Last year, Diabetes Australia endorsed a food-labeling program that includes GI ratings. That group and the Canadian Diabetes Association both say people with diabetes may benefit from using the index. And a joint pane) of the World Health Organization and United Nations Food and Agriculture Organization stated early this year that eating low-glycemic foods may stave off weight gain and guard against diabetes.
None of Agatston's support, though, comes from the U.S. medical establishment. The American Diabetes Association, for instance, says there is insufficient evidence for the GI's use.
Still, the South Beach diet may have advantages over other, older plans that already lean on the glycemic index, such as The Zone, Sugar Busters!, and, to some extent the Atkins diet. The South Beach regimen calls for more whole grains, fruits, and vegetables than these diets, along with oils and nuts high in poly- and monounsaturated fats. It also contains very little saturated fat. Too, Agatston is stronger on moderation than denial. Instead of banishing pasta, for example, he counsels dieters to eat small amounts. Rather than forbidding meat, he recommends low-fat cuts, plus plenty of fish.
The crucial point is that foods with lower GI ratings are generally healthier than those with higher values. So using the glycemic index as an overall guide to food choices makes sense. "It's not perfect," Agatston concedes, "but it's the best gauge we have."
Translation: Do you love plain bagels? Think of them as an indulgence. Eat them less often than you do oat-bran bread, whose GI value is one-third lower. Need a convincing reason to eat more vegetables? Virtually all of them have low GI numbers, and they may just keep you feeling fuller longer.
The approach worked for Carol Berns. After she started using Agatston's guide, she never turned back. She's been sold by more than the weight loss. "Someone who didn't know I was on a diet said I was walking faster than I used to," she says. "I've never had so much energy."