Insulin Levels May Dictate Success With a Diet

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Overall, no differences in weight loss were found between the lower carb group and the low-fat group.

But those with above-average insulin levels lost more weight on the lower carb diet -- 12.8 pounds at 18 months -- than those on the low-fat diet -- 2.6 pounds at 18 months.

The lower-carb plan also improved high-density lipoprotein or HDL cholesterol, the so-called good cholesterol, and triglycerides, more than the higher-carb, lower-fat plan. But the low-fat diet improved so-called bad (LDL) cholesterol more than the lower-carb plan.

Overweight people who can't lose weight or keep it off on a traditional low-fat diet might do better on a low-glycemic load diet, Ebbeling said.

Exactly why isn't known, she said.

A low-glycemic load diet emphasizes carbs with a low-glycemic index. The term low-glycemic index refers to the quality of carbs and how fast they are absorbed. Foods with a low-glycemic index are absorbed more slowly, thus keeping insulin levels more stable, she said.

To eat a low-glycemic load diet, avoid foods such as white bread, refined cereal, cookies and sugary drinks, Ebbeling advised. Emphasize fruits, vegetables, legumes and minimally processed grains, she said.

Lona Sandon, a spokeswoman for the American Dietetic Association and assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center at Dallas, said, "This study solidifies what was felt or anecdotally known by experts."

One caveat, she added, is that many people have no idea if they secrete more insulin than normal. "Just because you are overweight does not necessarily mean you are producing higher levels of insulin," she said.

Ebbeling said those who want to know their insulin-production levels can ask their doctor for an oral glucose tolerance test.

More information

To learn more about healthy eating, visit the American Dietetic Association.