Effect of Vestibular Stimulation on Fat Consumption and Energy Expenditure as Assessed Using Indirect Calorimetry
Condition: Obesity; Metabolic Syndrome
MeSH terms: Metabolic Syndrome
Study type: Interventional

Summary: 
      There is an ongoing and worsening problem with obesity in the developed, and much of the
      developing world. Although it has long been realized that Western diets that are rich in
      sugar and fat play an important role in this, it has only recently been realized that
      exposure to these diets, particularly in childhood, can damage the part of the brain that
      determines how much fat there is in the body. The result of this damage is that the so-called
      "set-point" for fat in this part of the brain is pushed upwards. There is a lot of evidence
      from animals that activating the brain's balance (vestibular) system pushes this set-point
      for fat downwards to cause fat loss, probably because this "tricks" the brain into thinking
      that there is increased physical activity. The aim of this study is to see whether
      non-invasive electrical stimulation of the vestibular system in human participants causes a
      change in metabolism of fat and/or energy expenditure, which, if regulated upwards, would
      suggest this could be used as a means of reducing body fat in humans.
    

Detailed description: 
      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.
    

Intervention name(s): Vestibular Nerve Stimulator; Sham stimulator
Intervention type(s): Device; Device
Intervention description(s): Electrical stimulation of the vestibular nerve with vestibular nerve stimulator (GVS device) for for 45 minutes using binaural mastoid placement.; Looks identical to vestibular nerve stimulator but discharges current into an internal resistor rather than activating the vestibular nerves.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Crossover design
Double-blind
Randomized
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: obesity; metabolic syndrome