Final answer:
Trans fats form during the hydrogenation of oils, where hydrogen is added, changing the double bond configuration from cis to trans, making the oil solid at room temperature. This increases the shelf life and stability of the oil, but it is linked to negative health effects like increased LDL cholesterol.
Step-by-step explanation:
Trans-fat forms during commercial processing of oils by a process called hydrogenation. This involves bubbling hydrogen gas through oils, which converts some of the naturally occurring cis double bonds into trans double bonds, thereby solidifying the oil. Partially hydrogenated oils contain trans fats because the hydrogenation process is not complete, leaving some double bonds in the trans configuration. This process changes both the physical consistency and the chemical properties of the fats, making them more desirable for various processed food products because of their increased shelf life and stability.
However, consumption of trans fats is linked to increased levels of low-density lipoprotein (LDL) cholesterol in the body, which is a risk factor for heart disease. As a result, nutritionists recommend limiting the intake of foods containing partially hydrogenated oils.