- The Washington Times - Friday, March 7, 2003

Most people feel full about 10 minutes after they begin eating, but it can take the brains of obese people 15 minutes to get the message, research shows.

The finding of a delayed feeling of fullness could explain why some fat people eat more, scientists at the University of Florida conclude in their report, published this month in the journal Psychiatric Annals.

"I cannot say this is the primary factor in obesity, since there are many factors. But it's probably one cause," said Yijun Liu, an assistant professor in the UF College of Medicine's psychiatry department at the McKnight Brain Institute and the study's lead investigator.

The researchers used magnetic resonance imaging (MRI) to pinpoint when the brain responds to changing hormone levels in the body that signal satiety.

One of the nation's foremost obesity specialists said the findings are significant.

"They are focusing on what could be the most important part of food intake [as it relates to obesity]. … That's satiation, rather than hunger," said Dr. Richard L. Atkinson, president of the American Obesity Association and director of MedStar's Obesity Institute.

"In research, we haven't appreciated satiety," Dr. Atkinson added.

The Florida researchers used an MRI method known as temporal clustering analysis to identify the point of satiation for a total of 30 adult volunteers: 10 who were obese and 20 who were normal weight. The term obese usually means being about 30 or more pounds overweight.

After the first five minutes of scanning, each volunteer was given glucose to stimulate what is called the "food response" in the hypothalamic region of the brain. The responses to food were both "weaker" and "slower" in the obese people's brains, Mr. Liu said.

He said it appears the additional time required for a heavy person to feel full fluctuates depending on his size.

To date, he said, an extra five minutes has been the maximum. But he said he suspects the delay could be longer in drastically overweight people.

Dr. Atkinson said other evidence indicates that focusing on satiety is a proper approach. He noted that most anti-obesity drugs on the market today are appetite suppressants.

He sees the likelihood that both future drugs and behavioral modification programs for the obese could be directed at making them feel fuller faster.

Dr. Atkinson said surgery is currently the best treatment for serious obesity.

For those interested in countering the effects of a slowness to feel full, Mr. Liu recommends that the obese "eat only when hungry, slow the pace of meals and learn to appreciate smaller portions."

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