Food faddism and fad diet are terms which refer to the tendency for idiosyncratic diets and eating patterns. A fad diet is supposed and promoted to improve health but often has the opposite results, if it is nutritionally unbalanced and unconfirmed by science.
Very often religious beliefs may affect somebody's choice of diet. For example, kosher or halal restrictions on the slaughter of meat, and the forbidding of the consumption of certain foods, notably pork. Psychological emotional states may also affect somebody's decisions on his or her diet.
Some of the scientific community say that food faddism is a product of humans' ignorance about basic scientific dietary facts.