Near-Infrared Spectroscopy: A Free-Living Neuroscience Tool to Better Understand Diabetes and Obesity

The human brain is the least accessible of all organs and attempts to study it in vivo rely predominantly on neuroimaging. Functional near-infrared spectroscopy (fNIRS) allows for the study of cortical neural activity in a non-invasive manner that may resemble free-living conditions. Moreover, compared to other neuroimaging tools, fNIRS is less expensive, it does not require the use of ionizing radiation, and can be applied to all study populations (patients suffering from claustrophobia, or neonates). In this narrative review, we provide an overview of the available research performed using fNIRS in patients with diabetes and obesity. The few studies conducted to date have presented controversial results regarding patients with diabetes, some reporting a greater hemodynamic response and others reporting a reduced hemodynamic response compared to the controls, with an unclear distinction between types 1 and 2. Subjects with obesity or a binge eating disorder have reduced prefrontal activation in response to inhibitory food or non-food stimuli; however, following an intervention, such as cognitive treatment, prefrontal activation is restored. Moreover, we discuss the potential of future applications of fNIRS for a better understanding of cortical neural activity in the context of metabolic disorders.

Automated summary

The human brain is difficult to access directly, so neuroimaging techniques like functional near-infrared spectroscopy (fNIRS) are commonly used for in vivo studies. fNIRS is a non-invasive and cost-effective method that can be applied to various study populations. Research using fNIRS in patients with diabetes and obesity has yielded conflicting results, with some studies finding increased hemodynamic response and others finding reduced response compared to controls. Additionally, individuals with obesity or binge eating disorder show reduced prefrontal activation, which can be restored with cognitive treatments. Further applications of fNIRS in metabolic disorders are also discussed.