Insulin Levels May Dictate Success With a Diet

People who secrete more of the hormone benefit from a lower-carb, higher-fat plan, study finds.

By Kathleen Doheny
HealthDay Reporter
Tuesday, May 15, 2007; 12:00 AM

Copyright © 2007 ScoutNews, LLC. All rights reserved.

TUESDAY, May 15 (HealthDay News) -- A diet slightly higher in fat and lower in processed carbohydrates -- such as refined cereals, white bread and white sugar -- may help people who secrete insulin at higher levels lose more weight than a low-fat, higher-carb plan.

That's the conclusion of a new study that may help to explain why a person's rate of insulin production -- and not dedication to a diet -- can determine their weight loss success.

In the study, those with higher insulin levels lost nearly five times as much weight on the lower-carb plan than on the low-fat plan, dropping 12.8 pounds in 18 months compared to just 2.6 pounds.

The study findings are published in the May 16 issue of the Journal of the American Medical Association.

Cara Ebbeling, co-director of obesity research at Children's Hospital Boston, and her colleagues followed 73 obese young adults -- ages 18 to 35 -- during a six-month intervention and then over 12-months of follow-up. They wanted to look at individual differences in insulin secretion and see if different diet plans worked better, depending on a person's levels of insulin -- the hormone that converts blood sugar to energy for cells.

The key question, Ebbeling said, was, "Why do some people have success with low-fat diets and others don't? We hear that question all the time. The usual explanation is that some people are more motivated than others."

But there may be more to the story than simple motivation, her research suggests. "Biology offers another explanation for why some people succeed with a conventional low-fat diet and others do not," she said.

Differences in insulin secretion are at least part of the reason why some overweight people don't have success with low-fat diets, Ebbeling said.

For the study, half the participants followed a diet that was 55 percent carbohydrates and 20 percent fat. The other half ate a diet that was 40 percent carbohydrates and 35 percent fat. At the study's start, the researchers measured the participants' blood levels of insulin after they had been given a 75-gram oral dose of glucose.