Can a Low-Glycemic Diet Help You Lose Weight?

Can a Low-Glycemic Diet Help You Lose Weight?//Food spread ((C) Healthday.com)

How often have you seen the following fine print under the before-and-after photos in diet ads?

Individual results may vary.

New medical research is giving some clue as to why that might be so.

A study in the May 16 Journal of the American Medical Association (JAMA) finds that the rate at which the body produces the hormone insulin – the substance that helps control how much sugar is in the blood -- can be a big factor in dieting success.

Obese young adults who produced relatively more insulin after eating -- a common condition called hyperinsulinemia -- lost an average of nearly 13 pounds over 18 months while on a diet that had them cut back on white breads, refined sugar and other "simple" carbohydrates.

On the other hand, this group lost an average of just 2.6 pounds when placed on the low-fat regimen. And obese people with normal insulin responses showed little difference in terms of weight loss results between the low-fat and low-glycemic load diets, according to researchers at Children's Hospital Boston.

"This study really shows us what we all think -- that there's no one perfect diet for everybody to lose weight," commented Connie Diekman, RD, director of nutrition at Washington University in St. Louis. "It also shows that food choices really can make a difference."

Insulin Was Key

In its research, the Boston team had 73 obese individuals ages 18 to 35 stay with one of two diets for 18 months. Half of the participants enrolled on a typical low-fat regimen where they avoided greasy fare and instead got most of their calories from carbohydrates (55 percent of daily intake) or protein (25 percent).

The other group ate what dietitians call a "low-glycemic load" diet, which is often used to help maintain healthy blood sugar levels.

Forty percent of caloric intake in this diet came from "complex" carbohydrates. "These are foods containing carbohydrates that are broken down and digested much more slowly, allowing for insulin release to be more gradual," Diekman explained. Complex carbohydrates tend to have a higher fiber content and include vegetables, legumes, some fruit, nuts, beans and high-fiber breads.

"Simple" carbohydrate foods that produce a sharp, rapid post-meal spike in insulin -- white breads, cakes, cookies, candies -- were shunned by those on the low-glycemic diet. The rest of the diet was taken up with fat (35 percent) and protein (25 percent).

The results: People whose glucose tests pegged them as high-insulin producers dropped an impressive amount of weight while on the low-glycemic load diet, but much less on the low-fat regimen. Perhaps even more impressive, this group was able to keep the weight off throughout the full year-and-and-a-half of the study.

Hyperinsulinemic people also got an added bonus: a significant bump in blood levels of HDL ("good") cholesterol, along with a healthy decline in blood fats called triglycerides while they were on the low-glycemic load diet. They experienced no such drop in levels of LDL "bad" cholesterol, however, probably due to the 35 percent fat intake allowed in the diet.

No 'One-Size-Fits-All'

Why the big difference in weight-loss success?

"Generally speaking, high insulin levels cause fat to be deposited and can even cause you to be hungrier," explained New York City-based dietitian Bonnie Taub-Dix, a spokeswoman for the American Dietetic Association. "So, foods that encourage a greater insulin secretion -- refined, sugary foods -- could actually prevent you from getting the weight loss you're trying so hard to attain."

And because hyperinsulinemic folk are prone to producing high levels of insulin in the presence of simple carbs, it makes sense that they would benefit most from a diet that avoids such fare.

The experts said that -- in the future -- gauging your personal insulin production level could help doctors determine the weight-loss strategy that's best for you. Right now, however, it's tough to find out if you are hyperinsulinemic or not since the test is not routinely offered.

"Doctors can do a glucose load test, but they are not likely going to do it without cause," Diekman said. "So, my advice as a dietitian would be to definitely go in and talk to your doctor about what the study demonstrated and what impact it might have on you. And then talk about the next step."

She said it's also time to bury the myth of the "one-size-fits-all" diet, and to stop blaming diet failures solely on lack of willpower.

"That's a really important point from this study -- that we don't have the answer to weight loss for everyone," Diekman said. "It's all about finding what works best for you and then doing it in a healthy way."