Food industry began to produce margarines (which include trans fats) as a replacement for butter because the latter had been declared a health hazard due to its high saturated fat content. Industry needed an alternative for their frying and baking needs. Adding hydrogen to unsaturated oils created a semi-solid, trans fat product, e.g. Crisco, that was shelf-stable and made flakey baked goods and crispy fried chicken. Unfortunately, trans fats turned out to be worse than butter with regards to heart disease risk (See “Why are trans fats bad for my heart?”). Now there is an effort to replace trans fats with alternatives, such as palm oil and, you guessed it, butter. The pendulum swings.