Trans fats or trans fatty acids (TFA) are a type of fat found naturally in meat and dairy products. Trans fat are also produced artificially produced in industries through a process called partial hydrogenation. Hydrogenation is the process of adding hydrogen atoms to unsaturated vegetable oils to attain saturation, which changes the fat properties such as  melting point, shelf life, flavour, etc. Hydrogenated fats have increased shelf life and reduced susceptibility to rancidity. They are also expected to enhance the taste of food. These processed oils are solid at room temperature, and melt upon heating or baking. Trans fat-rich products include vanaspati, margarine, vanaspati cream, vanaspati puff, etc. These industrial trans fats are available for both domestic and commercial purposes. Most foods that are baked, deep fried, canned, frozen, and ready-to-use products such as creams and doughs are made using trans fat substances.

A brief history of trans fat
The process of hydrogenation of oil to form semi-solid fat was invented in 1901. This fat later came to be known as trans fat. Unsaturated fats were vulnerable to rancidity (caused   due to exposure to air, light, and temperature difference) and the food industry felt the need to manufacture a stable form of unsaturated fats that had extended shelf life. During World War II the production of margarine increased so as to substitute butter which was rationed.  In the 1980s, there were advocacy campaigns claiming to remove saturated fats such as tallow, lard (fat from beef, pork, etc.) from fast-food businesses and replace them with trans fat-based products that had better smoke point. This was believed to be healthier! From then on, manufacturing of trans fat based products such as  pizza, potato chips, margarine, vanaspati has continued at a rapid pace.
 
How does consumption of trans fat increases the risk of cardiovascular disease? 
Cholesterol or blood cholesterol is a fat-like substance produced by the liver, which helps perform bodily functions such as synthesising hormones or digesting complex foods. Cholesterol is transported through the bloodstream in packages known as lipoproteins. The two main types of lipoproteins in the human body are Low Density Lipoproteins (LDL) and High Density Lipoproteins (HDL). HDLs, popularly known as the ‘good’ cholesterol, collect excess cholesterol in the bloodstream to the liver, which sends it out as excreta. LDLs, also called as ‘bad’ cholesterol deposit the cholesterol along the inner arterial walls of the blood vessels. Intake of trans fat-rich products like sweets, savouries, bakery items accelerate the cholesterol deposition process in the inner walls of arteries. This cholesterol accumulates in the form of cluster over the course of time and restricts blood flow. Scientific studies show that consuming food items high in trans fat can increase LDL levels and decrease HDL levels in the body thereby increasing the risk of cardiovascular disease in adults. On a global scale, more than 500,000 people die because of cardiovascular diseases that are caused due to intake of trans fat rich food says World Health Organisation (WHO). Considering trans fat a silent killer, it is significant to consume foods with very low or zero trans fat to lead a healthier life.