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16-08-2011 | General practice | Article

High levels of brown fat may protect against obesity in children

Abstract

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MedWire News: Increasing the amount of brown fat in children may be an effective approach for combating the ever-increasing rate of obesity and diabetes in children, say US researchers, after finding that lean children have a higher percentage of metabolically active brown adipose tissue (BAT) than obese children.

Previous research suggests that activation of BAT improves metabolism and the efficiency of energy expenditure, explained study author Aaron Cypess from the Beth Israel Deaconess Medical Center in Boston, Massachusetts.

Active BAT is present at consistently higher levels in lean adults compared with obese adults, leading to the suggestion that it may protect against obesity, she added.

Levels of active BAT are present at higher levels in children than in adults. Laura Drubach, also from the Beth Israel Deaconess Medical Center, and co-authors therefore investigated whether the prevalence and factors affecting the detection of active BAT in 172 children and young adults aged 5 to 21 years (mean age 14.2 years) were similar to those previously observed in adults.

The team used 18F-fluorodeoxyglucose positron emission tomography (PET) to measure BAT activity. Mean BAT activity was 43.3% in the boys and 45.3% in the girls tested, but peaked in those in the 13.0 to 14.9 year age group. The mean rates observed for children in this study are much higher than those seen in adults under similar conditions who generally have a rate lower than 10%, the authors note.

Drubach and colleagues observed a significant inverse correlation between body mass index percentile and BAT activity.

"We believe that the ability to noninvasively evaluate brown fat activity in vivo with PET imaging provides a better understanding of its prominent role in pediatric physiology, and may possibly provide insights into the treatment of childhood obesity," said Drubach.

"We might be able to combat the obesity and diabetes epidemics if we find safe ways of increasing brown fat activity," commented Cypess. "This might be an additional tool in the fight."

Unlike in previous studies in adults, no significant links between air temperature and BAT activity were observed in this study.

Cypess conceded that there are many questions that still need answering, such as whether children have more active BAT because they are thin or are thin as a result of having more BAT.

"That's the billion dollar question," he said. "But we do know that brown fat is a core component of pediatric and likely adult metabolism."

The authors conclude that having the ability to noninvasively assess BAT activity in vivo will help improve understanding about its role in pediatric physiology and obesity.

By Helen Albert

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