The latest weight loss news comes down on the side of so-called "good" carbohydrates — the kind offering more than sweet tastes and flash-in-the-pan bursts of energy with few nutrients.
The type of carbohydrate you eat, rather than the total amount of carbohydrates in your diet, may be related to body weight, say scientists in the American Journal of Epidemiology's Feb. 15 edition.
Call it the victory of broccoli over white bread, or lentils over linguine. Carbs with a lower glycemic index were kinder to weight than those with high glycemic index.
Glycemic index (search) is an indicator of how quickly a food affects blood sugar levels. Foods with a high glycemic index tend to be starchy, sugary, or refined and stripped of some of their natural goodness; they're often "empty" calories. In general, low-glycemic-index foods usually have more fiber and nutrients.
For instance, french fries have a higher glycemic index than grapefruit. Cakes and cookies are off the charts compared with spinach.
You may have heard of the glycemic index before. It's often mentioned in diets such as the Atkins and South Beach diets. Even if the phrase is new, you're bound to be aware of the carbohydrate consciousness of recent years.
Some people lump all carbs together, branding them as suspects in America's weight crisis. But all carbohydrates are not alike, and the new study clears the name of "good" carbs.
The study was conducted by researchers including Yunsheng Ma, PhD, MPH, of the University of Massachusetts Medical School (search). Participants were 572 healthy adults in central Massachusetts.
For one year, subjects gave quarterly reports on their food consumption and physical activity for seven-day periods. The data was collected between 1994 and 1998.
Is Glycemic Index the Key to Weight Loss?
The researchers looked at what the participants ate, how much they worked out, and their body mass index (BMI), a measure of total body fat. BMI is used to assess heart disease risk.
Higher BMIs were associated with diets that had higher glycemic index foods.
Daily carbohydrate intake and percentage of calories from carbohydrates didn't matter.
The study indicates that the type of carbohydrate — noted by glycemic index — was what counted, say the researchers. Short-term weight loss studies have echoed that result, but "the long-term effect of glycemic index and total carbohydrates on body weight is currently unknown," say Ma and colleagues.
The finding is consistent with the idea that foods with a higher glycemic index trigger more insulin production and more fat storage, say the researchers. However, they don't endorse cutting all carbohydrates or focusing on glycemic load for weight loss. Instead, glycemic index was most important, say the scientists, calling for more research.
Finding Foods' Glycemic Index
The glycemic index of various foods is listed online, but it's not required on food labels. A low glycemic index is considered to be 55 or less. The medium range falls from 56 to 69. High glycemic index is 70 or higher.
However, when it comes to the glycemic index of a particular food many factors come into play. For example, what else was eaten with the food and other components of a food including the amount of proteins and fats, as well as, how a food was prepared often alters the index.
No time to research your menu? Generally, unprocessed foods such as fruits, vegetables, lean meats, and whole grains have lower glycemic indices than processed or refined items.
It might also help to expand your definition of carbohydrates. Bread, pasta, rice, cereals, sweets, and grains don't have the market cornered. Fruits, vegetables, and legumes (search) also contain carbohydrates, and they may be the type to favor, along with fiber-rich whole grains.
If you're watching your weight, don't forget about calories. You'll still need to burn more calories than you consume to lose weight. Exercise will help with that part of the equation.
By Miranda Hitti, reviewed by Brunilda Nazario, MD
SOURCES: Ma, Y. American Journal of Epidemiology, Feb. 15, 2005; vol 161: pp 359-367. Glycemic Index. News release, University of Massachusetts Medical School.