(Vienna, 29 October 2021) Not every person with overweight has the same metabolic risk and brown fat could make the difference. A study led by Florian Kiefer's research group from the Division of Endocrinology and Metabolism of the Department of Medicine III at MedUni Vienna and Vienna General Hospital shows that people with obesity who also have active brown fat have a healthier metabolism and burn more energy than obese individuals without brown fat. The new findings suggest that the presence of brown fat may protect against obesity-related health complications. The study has just been published in the international top journal "Diabetes".
Medical researchers have been trying to understand for years why some people with obesity are less likely to develop health conditions such as diabetes or high blood pressure than others despite similar body weight. It now seems brown fat may be an important factor driving this "metabolically healthy obese phenotype”
“In contrast to white fat, which comprises more than 90% of the body fat and mainly stores energy, brown fat has beneficial metabolic effects because it can burn energy in the form of heat. Particularly, small infants use brown adipose tissue for heat production to maintain their body temperature but the proportion of brown fat in the body decreases with age and excess weight," explains Florian Kiefer.
However, in the recently published study, the Austrian research group discovered that more than a third of the adults with severe obesity (BMI > 35kg/m2) still had active brown fat. Therefore study participants were first exposed to moderate cold using cooling vests to activate brown fat, which was then detected by PET-CT scanning.
"In adults, brown fat is predominantly found at the base of the neck and in the rib cage. A short period of moderate cold stimulation of about an hour is sufficient to activate it," said the principal investigator Kiefer. Participants with obesity and active brown fat had higher energy consumption, less harmful abdominal fat, healthier glucose metabolism and fewer signs of fatty liver disease compared to a control group of similar body weight but with no detectable brown fat.
Kiefer comments: "It is quite amazing that individuals with active brown fat performed better in almost all metabolic tests, even though they had a slightly higher BMI. These data once again show us that it is not just the quantity of adipose tissue that matters but even more so the quality."
In fact, differences in body fat distribution may have contributed to the advantageous metabolic profile. In particular, the proportion of the intra-abdominal fat (visceral fat), which represents a high risk for diabetes and heart disease, was significantly lower in the group with active brown fat. "It is possible that through its increased metabolic activity, brown fat preferentially breaks down and burns the deleterious visceral fat stores. That is why we are currently working hard to develop new pharmacological treatments to activate brown fat," explains Kiefer.
MedUni Vienna scientists from the Departments of Biomedical Imaging and Image-guided Therapy and Surgery and from the Department of Laboratory Medicine were also involved in the study. The study was financed by the Austrian Science Fund (FWF), the Medical Science Fund of the Mayor of the City of Vienna and the Austrian Diabetes Society.