margarine were healthier than the saturated fats of butter. As early as 1956, there were suggestions in the scientific literature that trans fats could be a cause of the large increase in coronary artery disease but after three decades the concerns were still largely unaddressed. Instead, by the 1980s, fats of animal origin had become one of the greatest concerns of dieticians. Activists, such as Phil Sokolof, who took out full page ads in major newspapers, attacked the use of beef tallow in McDonald's French fries and urged fast-food companies to switch to vegetable oils. The result was an almost overnight switch by most fast-food outlets to trans fats. Studies in the early 1990s, however, brought renewed scrutiny and confirmation of the negative health impact of trans fats. In 1994, it was estimated that trans fats caused at least 20,000 deaths annually in the U.S. from heart disease. Mandatory food labeling for trans fats was introduced in several countries. Campaigns were launched by activists to bring attention to the issue and change the practices of food manufacturers. In January 2007, faced with the prospect of an outright ban on the sale of their product, Crisco was reformulated to meet the U.S. Food and Drug Administration (FDA) definition of "zero grams trans fats per serving" (that is less than one gram per tablespoon, or up to 7% by weight; or less than 0.5 grams per serving size) by boosting the saturation and then diluting the resulting solid fat with unsaturated vegetable oils. Structure A fatty acid is characterized as either saturated or unsaturated based on the respective absence of presence of C=C double bonds in its backbone. If the molecule contains no double C=C bonds, it is said to be saturated; otherwise, it is unsaturated to some degree. The C=C double bond is rotationally rigid. If the hydrogen bonded to each of the carbons in this double bond are on the same side, this is called cis, and leads to a bent molecular chain. If the two hydrogens are on opposite sides, this is called trans, and leads to a straight chain. See figures below. Because trans fats are more linear, they crystallize more easily, allowing them to be solid (rather than liquid) at room temperatures. This has several processing and storage advantages. In nature, unsaturated fatty acids generally have cis configurations as opposed to trans configurations. Saturated fatty acids (those