What causes a food to have trans fat?

Trans fats are created during the hydrogenation process, where hydrogen is added to liquid vegetable oils to make them more solid and stable, which extends shelf life. This process alters the chemical structure of the fats, resulting in trans fatty acids. Trans fats can also occur naturally in small amounts in some animal products. Foods like margarine, baked goods, and fried foods often contain artificial trans fats due to this process.