The Effectiveness of Transcutaneous Electrical Nerve Stimulation of the Auricular Branch of the Vagus Nerve in Loss Weight and Improving the Quality of Life in Patients With Obesity

Obesity is one of the leading causes of disability and death worldwide. In 2016, more than 1.9 billion adults were overweight, according to the World Health Organization. According to current projections, by 2030, 60% of the world's population (that is, 3.3 billion people) may be overweight (2.2 billion) or obese (1.1 billion), if trends in obesity continue.

In 2021, the journal Nature Communications published data on the effectiveness of the use of an invasive device that stimulates the efferent fibers of the vagus nerve of the stomach with light fluxes and thereby reduces the severity of hunger. In addition, in small clinical trials in patients with depression and epilepsy treated with transcutaneous vagus nerve stimulation, this procedure has been shown to lead to significant weight loss.

Although the mechanisms are not fully understood, it is believed that a high-calorie diet contributes to the desensitization of the vagus afferent fibers to peripheral signals and leads to a decrease in the constitutive expression of orexigenic receptors and neuropeptides. Violation of signal transmission along the afferent fibers of the vagus nerve may be sufficient for the development of hyperphagia and obesity, and stimulation of the vagus nerve, respectively, can be used in the treatment of these conditions. Recent discoveries revealed a new and important role of the vagus nerve within a physiological mechanism that utilizes afferent and efferent signaling in controlling cytokine levels and inflammation - the inflammatory reflex.

Afferent vagus nerve projections to the GI tract and the hepatic portal system play a major role in communicating alterations in peripheral metabolic homeostasis, including changes in cholecystokinin, lipids, leptin, insulin and glucose levels to the brain. In a reflex manner, efferent vagus nerve innervations of the heart, liver and pancreas provide cardio-metabolic regulatory output. Cholecystokinin- and leptin-induced afferent vagus nerve activity importantly mediates satiety and regulates feeding behavior. Cholecystokinin, released as a result of intestinal lipid accumulation also causes activation of afferent signaling and subsequent efferent vagus nerve output to liver that suppresses hepatic gluconeogenesis.

Transcutaneous vagus nerve stimulation (TENS) involves the stimulation of the left and/or right auricular branch of the vagus nerve in the area of the cymba concha with low-frequency electrical impulses. The auricular branch of the vagus nerve runs superficially, which makes it a favorable target for non-invasive stimulation techniques to modulate vagal activity. It gained popularity due to minimal side effects and low cost.