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 If
you're not diabetic or at high risk of developing Type 2 diabetes,
you may never have heard of the glycemic index. Yet understanding
this carbohydrate food-ranking tool can help you lose pounds
and keep them off--whether you have diabetes or not.
"In
general, the glycemic index is a measure of how much and how
fast a food raises the blood sugar level," says Osama
Hamdy, MD, PhD, director of the Obesity Clinic, Joslin Diabetes
Center, Boston, MA. "Foods with a high glycemic index
rapidly spike blood sugar levels, while foods with a low glycemic
index can help control blood sugar."
Why is
this a problem if you don't have diabetes? When blood glucose
rises too high after a meal or snack, it overstimulates the
pancreas, increasing insulin production. Then your blood sugar
drops, causing you to crave high-glycemic carbohydrate foods
again. So you eat more and more of them. The craving cycle
triggered by high-glycemic foods not only adds extra pounds,
but also puts you at greater risk of developing diabetes.
Sound
familiar? Think about the mornings you grabbed a doughnut
(a high-glycemic food) for a quick breakfast instead of a
bowl of oatmeal (a lower glycemic choice). On the days you
started with a high-glycemic punch, you probably wanted another
pastry before lunchtime.
When
diabetics consume carbohydrates that are mostly low glycemic,
their blood sugar levels are better controlled and they can
achieve and maintain weight loss. What's more, in a group
of older adults with Type 2 diabetes, having a low-glycemic
meal produced better cognitive performance after eating compared
to one ranked as high-glycemic.
Cutting
all carbs isn't the answer
For just
a minute, let's enter the exciting world of carbohydrates:
We need carbohydrates for good health. These important dietary
components--found mostly as sugars, fibers and starches--give
us the fuel (glucose, or blood sugar) to be active. Carbohydrates
provide important vitamins, nutrients and soluble fiber, which
helps lower blood sugar and cholesterol. (Fiber is the only
carb that moves through your body without being digested,
or turning into glucose.)
Some
carbohydrate-dense foods (especially processed ones) can cause
weight gain. So, not too long ago, the low-carb battle cry
was sounded. Many people began drastically eliminating carbohydrates
from their diets.
Pounds
were shed, but often so was good nutrition. Dieters avoided
not only fudgy brownies, but also carbohydrate-containing
fruits, vegetables and whole grains. Instead, they chose protein-laden
foods with almost no carbohydrates, including meats and cheeses
that were high in saturated fat. Restrictive low-carb eating
was tough to sustain and the craze lessened.
During
this time, scientists were exploring more about the glycemic
index and the connection between carbohydrates, blood sugar
and weight. But Dr. Hamdy cautions against jumping on another
diet-theory bandwagon.
"I
don't want people to eat more food because it's low glycemic.
We need the energy (calories) from carbohydrates to be no
more than 40 percent (of total calories) per day," he
says.
The low-carb
diets went too low, Dr. Hamdy adds. Recent nutrition guidelines
from the Joslin Diabetes Center advise eating no less than
130 grams of carbohydrates per day. Protein should comprise
20-30 percent of total daily calorie intake, with most coming
from lean sources.
Categorizing
foods by glycemic response
How a
certain food affects your blood sugar results from its glycemic
index computed with the amount of carbohydrate it contains.
This is known as the food's glycemic load. It's possible to
eat something with a high glycemic index (such as carrots
or watermelon) but such a small amount of carbohydrate that
its glycemic load is very low.
The science
behind this is complicated. But, overall, "we have a
much better understanding of the types of carbohydrates that
people should eat," says Dr. Hamdy. "Now we are
moving away from high-glycemic carbohydrates to low ones."
High-glycemic
foods include:
- white
bread and other processed or refined-flour products
- baked
potatoes
- French
fries
- white
rice
- pasta
made from white flour
- sugar-sweetened
drinks
- candy
These
low-glycemic foods are better choices:
- high-fiber
fruits and vegetables (excluding white potatoes)
- whole
grains, and the cereals or breads made from them
- brown
rice
- lentils
- whole-grain
pasta
- black
beans
The University
of Sydney, Australia, provides a searchable database for hundreds
of foods, showing glycemic index, glycemic load and amount
of carbohydrates per serving, at www.glycemicindex.com.
More
tips:
- Switching
to low-glycemic carbohydrates is just one part of a weight
loss plan, Dr. Hamdy emphasizes. He also stresses cutting
portion sizes, increasing physical activity and reducing
daily food intake by 250 to 500 calories.
- The
glycemic index of a food can vary depending upon where it
was grown, how ripe it is, how it was stored or processed,
starch type, fat or acid content and even health factors
of the person consuming it.
- Fiber
is a carbohydrate, but does not raise blood sugar levels.
Eat lots of soluble fiber foods such as oatmeal, fresh fruits
and vegetables. These also lower cholesterol.
- Aim
to get 20-35 grams of fiber daily. If you are diabetic,
you can consume up to 50 grams a day. Unprocessed and whole-grain
foods are best sources, but fiber supplements such as psyllium
may be added.
- Proteins
have virtually no carbohydrates. Choose lean protein such
as fish, skinless poultry, nonfat or low-fat dairy products,
legumes and tofu. Avoid high saturated fat sources such
as beef, pork and high-fat dairy items.
- If
you're diabetic, or at high risk, a registered dietitian
specializing in diabetes can help you plan for healthy eating.
References
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