When it comes to carbohydrates, it’s not how much you eat, but which kind, that makes a difference to your bathroom scale, new research shows.

People who are overweight do not appear to eat more carbohydrates overall than people who weigh less, the researchers report in the American Journal of Epidemiology. However, they found that overweight people tend to eat more refined carbohydrates, such as white bread and pasta, which cause a rapid spike in blood sugar.

“Total amount of carbohydrate is not related to body weight,” Dr. Yunsheng Ma of the University of Massachusetts Medical School in Worcester told Reuters Health. “It’s the type of carbohydrate that’s important.”

These findings suggest that low-carbohydrate diets, which recommend people cut back on all carbohydrates, are missing the mark, Ma added.

“Carbohydrates are not the enemy,” he said in an interview. “But you have to watch the kind of enemy.”

Ma explained that refined carbohydrates are often found in processed foods that contain a lot of sugar. This type of carbohydrate has what’s called a high glycemic index, meaning it causes a rapid increase in blood sugar. The body stores that sugar in muscle, but if it is not used, it becomes fat, he noted.

In contrast, whole grains, fruits and vegetables have carbohydrates that don’t have such high glycemic index, Ma said.

In the report, Ma and his colleagues note that in the last 20 years, the rate of obesity has increased, despite the fact that people are eating less fat. To help investigate the role carbohydrates play in obesity, the researchers measured the height and weight of 572 healthy people, and asked them to regularly report what carbohydrates they ate. Ma’s team followed study participants for one year.

They found that people with a higher body mass index - a measure of weight that factors in height - tended to eat carbohydrates with a higher glycemic index. The amount of carbohydrates people ate had no influence on body mass index.

“Refined carbohydrates are no good, but the total amount of carbohydrates is okay,” Ma noted.

He added that some countries now include a food’s glycemic index on the labeling, which can be helpful for people trying to lose weight or deal with diabetes.

SOURCE: American Journal of Epidemiology, February 15; 2005