Can certain starches really aid weight loss?
By John Casey
WebMD Weight Loss Clinic - Feature
Reviewed By Michael W. Smith, MD
Just as we've been hearing more and more about good and bad fats, diet gurus are starting to talk more about good and bad carbohydrates. And word is getting around.
On her television show, Oprah Winfrey claimed to have lost weight by switching from bad carbs to good. Likewise, many diet programs, such as Body-for-Life, tout the health benefits of good carbs. But are there really such things as good and bad carbohydrates?
"Some carbs are better than others, but it's not really a question of one carb being 'good' and one being 'bad,'" says Jack Alhadeff, PhD, professor of biochemistry at Lehigh University in Bethlehem, Pa.
"If you're eating to get energy for physical activity right away, simple carbs -- pasta, white bread, processed cereals, and the like -- work well. If someone is heavy or wants to manage weight, it is smart to chose high-fiber carbohydrates."
Why? Because all carbohydrates are broken down into sugar, or glucose, which is the body's fuel. Carbohydrates with little fiber break down quickly. Those foods with carbohydrates trapped in fiber take longer to break down. The rate at which this happens can be represented on what nutritionists call the glycemic index.
Foods high on the glycemic index turn to glucose fast. But that speed can cause a spike in levels of the hormone insulin, which the body needs to process glucose into physical energy. Foods low on the index -- sweet potatoes, brown rice, leafy greens, fat-free milk -- break down slowly and result in lower insulin levels.
"Unless you're a diabetic, glycemic index may not be all that important," says Alhadeff, who adds that since most of us eat a variety of foods in a meal, the accuracy of the index can be questionable.
But what about the notion that glucose from high-index foods is more likely to be stored as fat?
"The scientific literature is very clear that eating carbohydrates that are embedded in plant cellulose -- complex carbohydrates -- is always better," says Nagi Kumar, PhD, director of clinical nutrition at the Moffitt Cancer Center and professor of human nutrition at the University of South Florida in Tampa. "But the reasons it is better are not because it somehow lessens or alters fat storage."
She says that fiber-rich carbohydrates increase the bulk of the meal, making you feel fuller. This in turn, helps moderate the amount of food you eat.
So, what is fiber, exactly?
There are two types of fiber: soluble and insoluble. Nutritionists describe soluble fiber as a sticky substance that is found in fruit, vegetables, dried beans and peas, and oat products. Insoluble fiber, which is gritty in texture, accounts for 70% of the fiber in our diets, mostly from wheat bran.
"We eat way too many calories and way too many empty calories," she says. "Fiber can help you avoid overeating. We've also found that fiber can bind with cholesterol in the digestive tract, thus lowering blood cholesterol."
Another important point about fiber-rich foods is that they tend to be loaded with phytochemicals that appear to have anticancer functions, says Kumar.
"Pertaining to cancer, we've found 65 or so non-nutrients and nutrients that have action against cancer," she says. "We've seen soy, lycopene, bicarbanol, to name just a few of these, have significant effect against various cancers."
Along with these benefits and its role in weight maintenance, fiber helps prevent the following:
- Diverticulosis -- an intestinal disease where pockets, which can become infected, develop in the intestinal lining
The next time you have a choice about what to buy at the store -- for instance, between fluffy, white bread and a dark, brown loaf of whole wheat -- what do you do?
"Buy the bread that you have to drag out of the store, because the loaf is so heavy and dense," says Kumar. "Everything comes down to the amount of fiber you can get into your food."
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