Effect of Vestibular Stimulation on Fat Consumption and Energy Expenditure as Assessed Using Indirect Calorimetry

There is a growing realization that obesity can, in many ways, be viewed as a neurological disease triggered by lifestyle factors. There is clear evidence that the central melanocortin system, which is centered in the arcuate nucleus of the hypothalamus, regulates a "set-point" for how much fat the body should have. It does so by altering appetite and metabolic rate so that deviations too far in either direction are strongly resisted. This set-point is determined by genetic, epigenetic and lifestyle factors. Thus, excessive exposure to dietary monosaccharides, such as glucose, and saturated fats, especially in childhood and adolescence, can damage the neurons of the arcuate nucleus and push the set-point up. This then can condemn sufferers to a lifetime of obesity, despite individual efforts to combat it using diet and/or exercise. Establishing a method of tuning down the set-point for body fat thus has to be a goal if the current obesity pandemic is to be successfully combatted. A significant amount of animal work suggests that stimulating the vestibular system in the inner ear, by means of chronic centrifugation, actually does just that and causes a reduction in body fat. This is likely because chronic vestibular activation is taken by the brain to represent a state of increased physical activity, and in order to optimize homeostasis it would be appropriate for the body to have a leaner physique, by reducing unnecessary energy expenditure from carrying excess fat. It is possible to stimulate the vestibular nerve in humans by applying a small electrical current to the skin behind the ears. This is an established technology that is believed to be safe, but only previously used for research purposes. The investigators found in a pilot study that recurrent stimulation of this kind for two or three hours a week over four months led to a statistically significant reduction in truncal fat in the active group as opposed to the control group who underwent sham stimulation. Given the current, and increasing levels of global obesity, it is important to determine whether non-invasive electrical vestibular nerve stimulation (VeNS), otherwise known as galvanic vestibular stimulation (GVS), is a viable treatment option, since if it were this would be of significant scientific importance. The investigators wish to use the technique of indirect calorimetry to explore this. This involves wearing a tight face mask to collect all inspired oxygen and expired carbon dioxide and using formulae to calculate total energy expenditure and the component of metabolism that is derived from fat as compared to carbohydrate.