What are the possible harmful effects of an unbalanced vegetarian diet?

Answer 1

Being a vegetarian at all is extremley UNhealthy and cannot benefit you in any way that will out weigh the harm of unhealthy weight loss and lack of proper vitamins and nutrients found in meat and eggs. -Circle of life

Answer 2

Vegetarianism is usually quite healthy. However, it is sometimes difficult to get all the amino acids, vitamins, and minerals your body needs without meat, or animal products.

Vitamin B12 in particular is difficult for vegetarians to get enough of... there's essentially none of it in plants (some plants produce compounds that are similar enough that the usual test for vitamin B12 will detect them as being vitamin B12, but they turn out to be different enough that they're inactive in the human body. In general, you should be skeptical of claims that a plant or yeast product contains B12 unless it's been specifically added).

Fortunately, B12 ultimately comes from bacteria, so there are vegan sources of it, but you need to specifically take it as a supplement or eat vegan products that are already fortified with it, like Marmite. (Marmite is a brewer's yeast product to which vitamin B12 from bacteria has been added.)