Active brown adipose tissue protects against 'pre-prediabete
Thirty-four healthy adult volunteers between the ages of 18 and 35 and with a body mass index (BMI) between 18 and 25 were enrolled in the study. Blood samples were taken, and lifestyle interviews were performed. To activate the brown fat, participants wore cooling suits to bring their body's temperature to just above the shivering point. After two hours, subjects removed the cooling suits and were imaging with FDG PET/CT. Post-cooling blood samples were also taken after removal of the cooling suits.

Activated brown fat was analyzed for each subject, and glucose, insulin, lipid and other metabolite levels were correlated with volume and intensity of the active brown fat. Using a median cut-off, participants were classified as having high brown fat levels or low brown fat levels. A higher level of activated brown fat was associated with early metabolic dysfunction. Pre-cooling glucose, insulin, thyroid stimulating hormone and triglyceride levels were significantly higher in the high brown fat group than the low brown fat group. In addition, a significant difference in BMI was found, with subjects with high brown fat levels having a higher BMI than subjects with low levels of brown fat. Those with low brown fat levels were more likely to report observing a controlled diet and exercising regularly.

In a prospective study of young, lean adults, PET/CT imaging revealed that higher levels of active brown adipose tissue (also known as "brown fat") are more prevalent in individuals who exhibit very early indications of metabolic disorders.