If we have vitamin B12 deficiency, then is it true that that will cause obesity?

No. Vitamin B12 deficiency can cause low red blood cell counts, neurologic complications and other assorted skin, energy and GI effects but not frank obesity.

Related Questions

Could Lewy body dementia be caused by Vitamin B12 deficiency?

Unrelated. Deficiency of B12 can cause dementia, but Lewy Body Dementia is a separate disorder. See this site for info on Lewy Body Dementia. Http://www. Mayoclinic. Org/diseases-conditions/lewy-body-dementia/basics/definition/CON-20025038.
Lewy body dementia. The etiology for Lewy body dementia is largely unknown, but it is not believed to be related to vitamin B12 deficiency that can cause otherwise significant neurological symptoms mimicking dementia. An overlap is always possible and vitamin B 12 deficiency should be corrected promptly. So far, there is no known cure for Lewy body dementia, treatment being mostly symptom directed.