There are many claims that Vitamin B-12 is linked to weight loss and that it boosts energy. Among other things, Vitamin B-12 does help the body convert fats and proteins into energy and aids in the breakdown of carbohydrates. It is true that a B-12 deficiency can lead to a number of ailments. Also, most B-12 sources are derived from animal-based sources so a deficiency is not uncommon among vegetarians and vegans; also, people who take the diabetes drug Metformin are at a higher risk for a B-12 deficiency. So, if you don’t eat meat, or you take Metformin, you may want to be tested for a B-12 deficiency.