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MRI Finds Hidden, High-Risk Fat in Teens

More precise estimates of deep fat can help predict their risk for disease

TUESDAY, Feb. 27, 2007 (HealthDay News) -- MRI may be an important new weapon in the fight against youth obesity, experts say.

The technology appears to be a fast and effective way to detect patterns of excessive intra-abdominal fat in children and teens, a new study finds.

"We found a technique that can determine the distribution of fat quickly," said study author Dr. Marilyn Siegel, a professor of radiology and pediatrics at Washington University School of Medicine, in St. Louis. The study is published in the March issue of Radiology.

The MRI technique is expected to be used as a research tool, not to enter mainstream practice. But determining the extent of this intra-abdominal, or visceral, fat to assess youngsters' heart disease risk is important, experts say. Too much of this fat can put children and teens at risk for developing heart problems, diabetes and other ailments, just as it can in adults.

Siegel's team used two types of MRI -- single-slice (which takes a few minutes) or multi-slice, which takes longer.

The team then compared them to two established methods used to measure fat distribution. These included anthropometry, which involves taking physical measurements such as waist circumference, abdominal height and body-mass index, or dual energy absorptiometry (DEXA), a whole-body scan that distinguishes lean mass from fat tissue. Anthropometry is not very precise, and DEXA involves exposure to radiation.

MRI might get around those problems, the researchers thought. "What we did was assess a fast technique to look at fat," said Siegel. Speed is important, she added, because "if you are looking at a child, you want to do [the exam] as fast as you can."

Siegel's team evaluated 30 children with the two different MRI techniques and the established techniques. The 20 boys and 10 girls were all between the ages of 10 and 18. Eleven were of normal weight without diabetes; 10 were overweight and had type 2 diabetes; nine were overweight but not diabetic.

The single-slice MRI gave as good results as the longer tests, she found. "Single-slice MRI is simple and fast and has the potential to be used in clinical research applications, such as monitoring treatment, planning patient management and implementing clinical trials," Siegel said.

Both the fast MRI and the more comprehensive scan correlated well with the results of established measurement methods, the team found.

In fact, the MRI exams gave better information, Siegel said. "The other methods are subject to observer error," she said. "They also give no information on the distribution of fat. The fact that you have a lot of fat in your arm doesn't mean you have a lot of fat in your abdomen."

The overall fat volume was found to be highest in the overweight teens with diabetes, she said.

"This is a preliminary step in defining or determining the methods of estimating fat," Siegel said.

Another expert, Dr. Bonita Franklin, a pediatrician and pediatric endocrinologist at the New York University Medical Center, said the MRI will serve as a useful research tool to detect intra-abdominal fat.

For instance, she said, researchers might use it to determine the effects of a particular diet plan on intra-abdominal fat -- measuring children's fat with the MRI before and after the diet.

While pediatricians can generally tell if a patient is overweight, using the MRI scan may give them a more precise picture, said Franklin, who is also chief of pediatric diabetes at Bellevue Hospital in New York and clinical assistant professor of pediatrics at New York University School of Medicine.

The MRI "correlated well" with the other methods, she said. And detecting how much visceral fat is there can help a pediatrician assess a patient's risk.

"We know from other research it's the visceral fat that's inside the body, in the abdomen, that is more highly correlated with risks of cardiovascular disease, high cholesterol, insulin resistance and diabetes risk," Franklin said.

Meanwhile, parents who suspect their children are too heavy should consult with their pediatrician and ask if their weight can be evaluated, he said, and put a plan into place if weight is found to be excessive.

According to the U.S. Centers for Disease Control and Prevention, the prevalence of overweight children has tripled in the United States in the past 30 years.

More information

To learn more about physical activity and youth, visit the U.S. Centers for Disease Control and Prevention.

SOURCES: Marilyn Siegel, M.D., professor, radiology and pediatrics, Washington University, St. Louis; Bonita Franklin, M.D., chief, pediatric diabetes, Bellevue Hospital, New York City, and clinical assistant professor, pediatrics, New York University School of Medicine, New York City; March 2007 Radiology
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