Many people start vegetarian and vegan diets without devoting an adequate amount of time to nutritional research and meal planning. As a result, a considerable amount of people who start vegetarian diets do not last for more than 1-2 months.

Although most vegetarians consume a considerable amount of protein, they often do not absorb as much as they would on a non-vegetarian diet. This is because plant proteins are considerably less digestible than animal proteins, which contain amino acid chains that are closer or identical to human amino acid chains.