 More recent research has shown that brown fat is related not to white fat, but to skeletal muscle.Studies using positron emission tomography scanning of adult humans have shown that brown adipose tissue is still present in most adults in the upper chest and neck (especially paravertebrally).The remaining deposits become more visible (increasing tracer uptake, meaning more metabolically active) with cold exposure, and less visible if an adrenergic beta blocker is given before the scan.