Production of hydrogenated fats increased steadily until the 1960s as processed vegetable fats replaced animal fats in the US and other western countries. At first, the argument was a financial one due to lower costs; however, advocates also said that the unsaturated trans fats of margarine were healthier than the saturated fats of butter. The Center for Science in the Public Interest (CSPI) campaigned against the use of saturated fats for fast food cooking starting in 1984. When fast food companies replaced the saturated fat with partially hydrogenated unsaturated fats, CSPI's campaign against them ended. While CSPI defended trans fats in their 1987 Nutrition Action newsletter, by 1992 CSPI began to speak against trans fats and is currently strongly against their use.