Vestibular Stimulation and Fat Loss

It is a strange but well replicated fact, that if you leave small animals in a centrifuge for a really long time, they lose a lot of fat.  Many of these experiments were done in the 1960’s and 1970’s as part of the study of the physiological effects of spaceflight.

Centrifugation makes animals smaller, leaner, more muscular, and denser-boned

If you put female rats in a centrifuge for 60 days, at 2.76 and 4.15 G (where G is the strength of Earth’s gravitational field), they lose 10% and 19% of their body weight, respectively, with reductions in the fat fractions of most components and increases in the water fraction of liver and gut.[1]

Female rats exposed to 3.5 or 4.7 G for one year showed “marked depletion of body-fat depots” and “significant decrease in kidney and liver lipids.”[2]

Chickens exposed to 1.75, 2.5, or 3 G for 24 weeks had significantly reduced body fat.[15]  The drop in body fat is linearly increasing in G, and also increases with body mass.[17]

Rabbits exposed to up to 2.5 G had a drop in body fat and increase in body water, even as their food consumption increased.[16]

Female rats centrifuged for 30 days at 2.76 or 3.18 G reduced body fat and fat-free body mass within the first week of centrifugation, without any difference depending on whether they were fed commercial chow, a high-fat diet, a high-protein diet, or fasted.[3]

The drop in body fat from centrifugation can be quite large; chickens went from 13% body fat to 3% body fat at 3G, and mice have a 55% drop in total body fat after 8 weeks of 2G exposure.[18]

Centrifuged mice have a drop in weight during the first few days, but slowly regain it.[10]  Hamsters born in centrifuges have a final body weight of about 30% lower than control hamsters.[13]

Female rats centrifuged for 810 days at 2.76 G grew more slowly than control rats, but had the same absolute muscle mass; they have thicker bones and larger muscles for their size than uncentrifuged rats.[4]  They also have denser bones.[6]  They have a higher proportion of slow-oxidating muscle fibers (the kind used in distance running and other endurance activities).[9]  Centrifuged dogs (subjected to 2G for 3 months) also have denser bones.[11]

Centrifuged rats also had more uptake of glucose into tissues and a stronger response to insulin than uncentrifuged rats; this is the opposite of “insulin resistance.”[5]  Centrifuged chickens also have higher glucose uptake.[14]

Centrifuged rats have a sharp decrease in body temperature at about 3 days, and a subsequent recovery of normal body temperature.[7]

Centrifuged rats have a prolonged decrease in locomotor activity and distorted circadian rhythms.[8]

Centrifugation alters the vestibular system

The vestibular system is involved in balance.

The microscopic structure of the lateral vestibular nucleus (where many vestibular nerve fibers enter the brain) is altered in chronically centrifuged rats.[12]  Centrifuged hamsters have impaired balance during swimming tests.[13]

Knockout mice that lack vestibular linear acceleration organs are known as “head-tilt mice.” They move normally, except for a head tilt, but cannot swim because they cannot orient to the gravitational force vector.  Head-tilt mice, when centrifuged at 2G, do not experience the changes that chronic centrifugation causes in wild-type mice: they do not have a drop in body temperature, body mass, or body fat percentage. While wild-type mice under 2G dropped from 16% to 8% body fat, head-tilt mice started out at 8% before centrifugation and did not change.  This implies that vestibular effects somehow cause the physiological changes associated with higher gravity.

Artificially stimulating the vestibular organs causes fat loss

A pilot study at the University of California San Diego’s Center for Brain and Cognition, one of whose authors was famed neuroscientist Vilayanur Ramachandran, tested galvanic stimulation of the vestibular nerves, a non-invasive procedure that involves passing current over the inner ear, on six overweight and obese subjects, with three controls, for a total of 40 hours, for an hour a day.  There was a significant 8.3% decrease in truncal fat and a nonsignificant decrease in total body fat.  Appetite was reduced, leptin was reduced, and insulin was increased.[19]

This is not a huge reduction in fat.  (It would be something like two pounds on me, over the course of a month.) On the other hand, this is a significantly lower “dose” of vestibular stimulation than centrifuged animals would receive. The animals that had body composition changes were centrifuged continuously over a period of months.  It may be possible to slowly increase the time spent receiving galvanic stimulation.

Vestibular stimulation may affect hormone levels

There are a few case studies from India of “controlled vestibular stimulation” (swinging on a swing) causing various changes in physiology. A college student for whom swinging resulted in significantly lower blood pressure, blood glucose, and cortisol[21], and an 83-year-old diabetic man for whom swinging resulted in significantly lower glucose and blood pressure [22].

The vestibular system modulates autonomic activity, and vestibular stimulation activates vagus nerves in the pancreas which stimulate insulin production. There seems to be a parasympathetic response to vestibular stimulation, which goes with increased insulin production and lower hunger, both of which would reduce fat.  (It also matches the intuitive observation that rocking and swinging is soothing: think of infants and rocking chairs.)

Other Vestibular Stimulation Weirdness

Galvanic vestibular stimulation also seems to reverse face blindness [23].

Conclusion

Galvanic vestibular stimulation is safe, if sometimes uncomfortable (causes motion sickness), and might have significant effects on body fat and other metabolic factors. It is probably worth investigating more on humans.

It’s trivial to set up; people who are interested in virtual reality frequently build their own vestibular stimulation rigs to increase the verisimilitude of immersive games.  This seems like something with a lot of potential for venturesome self-experimenters to try out as well as something to investigate seriously in clinical experiments.

References

[1]Pitts, G. C., L. S. Bull, and J. Oyama. “Effect of chronic centrifugation on body composition in the rat.” American Journal of Physiology–Legacy Content 223.5 (1972): 1044-1048.

[2]Oyama, J., and B. Zeitman. “Tissue composition of rats exposed to chronic centrifugation.” American Journal of Physiology–Legacy Content 213.5 (1967): 1305-1310.

[3]Pitts, G. C., L. S. Bull, and J. Oyama. “Regulation of body mass in rats exposed to chronic acceleration.” American Journal of Physiology–Legacy Content 228.3 (1975): 714-717.

[4]Amtmann, Eduard, and Jiro Oyama. “Effect of chronic centrifugation on the structural development of the musculoskeletal system of the rat.” Anatomy and embryology 149.1 (1976): 47-70.

[5]Daligcon, B. C., and J. Oyama. “Increased uptake and utilization of glucose by diaphragms of rats exposed to chronic centrifugation.” American Journal of Physiology–Legacy Content 228.3 (1975): 742-746.

[6]Jaekel, Erika, Eduard Amtmann, and Jiro Oyama. “Effect of chronic centrifugation on bone density of the rat.” Anatomy and embryology 151.2 (1977): 223-232.

[7]Oyama, J. I. R. O., WILLIAM T. Platt, and VARD B. Holland. “Deep-body temperature changes in rats exposed to chronic centrifugation.” American Journal of Physiology–Legacy Content 221.5 (1971): 1271-1277.

[8]Holley, Daniel C., et al. “Chronic centrifugation (hypergravity) disrupts the circadian system of the rat.” Journal of Applied Physiology 95.3 (2003): 1266-1278.

[9]Martin, W. D. “Time course of change in soleus muscle fibers of rats subjected to chronic centrifugation.” Aviation, space, and environmental medicine 49.6 (1978): 792-797.

[10]WUNDER, CHARLES C. “Survival of mice during chronic centrifugation.” Aerospace Med 33 (1962): 866-870.

[11]Amtmann, Eduard, Jiro Oyama, and Gerald L. Fisher. “Effect of chronic centrifugation on the musculoskeletal system of the dog.” Anatomy and embryology 149.1 (1976): 71-78.

[12]Johnson, J. E., W. R. Mehler, and J. Oyama. “The effects of centrifugation on the morphology of the lateral vestibular nucleus in the rat: a light and electron microscopic study.” Brain research 106.2 (1976): 205-221.

[13]Sondag, H. N. P. M., H. A. A. De Jong, and W. J. Oosterveld. “Altered behaviour in hamsters conceived and born in hypergravity.” Brain research bulletin 43.3 (1997): 289-294.

[14]Evans, J. W., and J. M. Boda. “Glucose metabolism and chronic acceleration.” American Journal of Physiology–Legacy Content 219.4 (1970): 893-896.

[15]Evans, J. W., A. H. Smith, and J. M. Boda. “Fat metabolism and chronic acceleration.” American Journal of Physiology–Legacy Content 216.6 (1969): 1468-1471.

[16]Katovich, MICHAEL J., and ARTHUR H. Smith. “Body mass, composition, and food intake in rabbits during altered acceleration fields.” Journal of Applied Physiology 45.1 (1978): 51-55.

[17]Smith, A. H., P. O. Sanchez, and R. R. Burton. “Gravitational effects on body composition in birds.” Life sciences and space research 13 (1974): 21-27.

[18]Fuller, Patrick M., et al. “Neurovestibular modulation of circadian and homeostatic regulation: vestibulohypothalamic connection?.” Proceedings of the National Academy of Sciences 99.24 (2002): 15723-15728.

[19]McGeoch, Paul D., Jason McKeown, and Vilayanur S. Ramachandran. “Modulation of Body Mass Composition using Vestibular Nerve Stimulation.” bioRxiv (2016): 087692.

[20]Yates, B. J., and A. D. Miller. “Physiological evidence that the vestibular system participates in autonomic and respiratory control.” Journal of Vestibular Research 8.1 (1998): 17-25.

[21]Sailesh, Kumar Sai, and R. Archana. “Controlled vestibular stimulation: A physiological method of stress relief.” Journal of clinical and diagnostic research: JCDR 8.12 (2014): BM01.

[22]Kumar, Sailesh Sai, R. Archana, and J. K. Mukkadan. “Controlled vestibular stimulation: Physiological intervention in diabetes care.” Asian Journal of Pharmaceutical and Clinical Research 8.4 (2015): 315-318.

[23]Wilkinson, David, et al. “Improvement of a face perception deficit via subsensory galvanic vestibular stimulation.” Journal of the International Neuropsychological Society 11.07 (2005): 925-929.

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5 thoughts on “Vestibular Stimulation and Fat Loss

  1. If this works, it’s a major breakthrough in obesity treatment. How often and for how long do you have to zap your inner ear to benefit?

    • Probably a really long time, to replicate the effects of centrifugation. I’m doing some home experiments to see if it’s tolerable and effective to have electrodes on your ears for a long time. The first thing I tried was a 9-volt battery and some homemade electrodes (aluminum foil + paper towels soaked in salt water). It did stimulate the nerves (I could feel the spinning sensation) but it was far too painful to keep on for more than a minute. My next attempt will be a TENS unit, which has real medical electrodes and adjustable voltage, and I’ll see if that’s more tolerable.

  2. Up until the point where you mention the head-tilt mice, my assumed model was that relevant difference with the centrifuged animals is energy expenditure: it takes more energy and more muscle to stand, walk around and pump blood under increased gravity, and this explains all the effects except maybe the circadian rhythm one.

    My priors around weight and nutrition are very different than most peoples’, and to me, “slight weight loss with reduced leptin” sounds like a bad thing. I say this because my pre-existing low-confidence interpretation of what leptin is, is that it’s the “make optional energy expenditures” signal; it turns on parts of the immune system, ovulation and puberty, and low leptin levels are correlated with depression. My best guess about how vestibular stimulation would cause weight loss would be that it causes nausea, which causes eating less, with all the associated ills.

    The head-tilt mice are a bit confusing, but one possibility is that both the wild-type and head-tilt mice have a homeostatic mechanism keeping their body fat percentage in the [8%,16%] range. I believe a mechanism like that exists, maybe not for that exact range, for unrelated reasons. Then the question would not be why the head-tilt mice stayed at 8%, but why they started there when the wild-type mice started at 16%. My speculative guess is that this is a sickness behavior; mice that feel healthy are willing to eat extra to store fat, while mice that feel sick act as though eating extra food is risky.

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