Optical imaging for brown or beige adipose tissue

Currently, one in three adults worldwide may be obese or overweight. Obesity is characterized by an excess of energy-storing white fat. An ingenious and sought-after strategy against obesity is to activate energy-consuming beige fat, which is converted from white fat or brown fat. However, existing tools for assessing brown or beige fat activation in vivo have certain limitations, such as being cumbersome and expensive. Optical imaging is a relatively straightforward and economical imaging technique that utilizes light to peer into the structural–functional information of living organisms at multiple scales. Despite the availability of various optical imaging modalities for detecting brown or beige fat, there is a dearth of literature summarizing relevant studies. Accordingly, this review focuses on these optical modalities and elaborates on their imaging principles, characteristics, and recent research advances in the detection of brown or beige fat. Their imaging targets, advantages, and disadvantages are further concluded. As a methodological reference, this review can guide the selection of optimal optical modalities to noninvasively profile brown or beige fat activation from a specific biological perspective, maximizing the potential of optical imaging in anti-obesity assessment.