Trans fats (trans fat) are the result of hydrogenation the liquid fraction of vegetable fat, by introducing the hydrogen bond of unsaturated fatty acid, forming trans isomers, causing the change of nutrient properties of fatty acids, by remaining only the energy source. They are used in hard margarine and food products (baked confectionery products). It is recommended to completely eliminate (or at least limit) the consumption of trans fats, because of their adverse effect on the human body (e.g. raise the level of total cholesterol, disturbed the balance between the factions of LDL and HDL, weaken the immunity of the organism and have a negative impact on the insulin metabolism, making it difficult to transport food into muscle cells, also there is noticed their influence on the development of cancer. Very rarely used in thermogenic sports supplements (i.e. energy bars).