Contrary to popular belief, not all fats  cause heart diseases and are bad. In fact,  

most fats, in adequate amounts, are required  for normal bodily functions, especially brain  

functions. There are also GOOD fats that actually  DECREASE the risks for cardiovascular diseases. 

A fat molecule is composed of a glycerol head and  three fatty acid tails, each of which is a long  

hydrocarbon chain - a carbon skeleton bound to  hydrogen atoms. When ALL the carbons are FULLY  

bound to hydrogens, the fatty acid is said to  be SATURATED - ALL the bonds between carbon  

atoms are SINGLE, and the hydrocarbon chain has  a STRAIGHT shape. A fat molecule made ENTIRELY  

of saturated fatty acids is a saturated fat.  Due to their STRAIGHT tails, saturated fats  

are COMPACT and solid at room temperature. On the other hand, when the hydrocarbon  

chain has FEWER hydrogens, it is said to be  UNsaturated. Instead of binding to a maximum  

number of hydrogens, some carbon atoms bind  to each other via a DOUBLE bond. The presence  

of double bonds may BEND the hydrocarbon  chain, creating GAPS between molecules,  

making them LESS compact. As a result, unsaturated  fats are usually liquid at room temperature. A  

fat molecule that contains ONLY ONE double  bond is a monounsaturated fat, while one  

that has MULTIPLE double bonds is POLYunsaturated. Dietary fats provide fatty acids for the synthesis  

of the cell membrane - a vital component of all  animal cells. The gaps in UNsaturated fatty acids  

provide membrane FLUIDITY, facilitating membrane  transport and cellular signaling. While both types  

of fats are needed for an optimal composition  of the cell membrane, too much saturated fat,  

which is commonly the case in a typical American  diet, would make the membrane RIGID and HINDER  

cellular responsiveness. Membrane fluidity is  most important in the nervous system, where  

neuronal response requires extremely fast cellular  communication. A certain ratio of UNsaturated to  

saturated fatty acids is also required for  the formation of myelin – the insulating  

material that wraps around axons of neurons and  speeds up the conduction of electrical signals. 

The body is capable of synthesizing all the  fatty acids it needs, with the exception of  

polyunsaturated fatty acids omega-3 and  omega-6, which must be obtained from the  

diet. These are known as essential fatty acids. In general, UNsaturated fats are HEALTHIER than  

saturated fats. UNsaturated fats DECREASE the  risks for heart disease by REDUCING the amount  

of BAD cholesterol, LDL, and INCREASING the  GOOD cholesterol, HDL; while saturated fats  

increase BOTH good and bad cholesterol. But  not all unsaturated fats are equal. In fact,  

a type of unsaturated fat, known as  TRANS-fat, is the UNhealthiest of all! 

A double bond can give rise to 2 possible  configurations: cis and trans. CIS is when  

the 2 hydrogen atoms are on the SAME side  of the bond, while TRANS is when they are on  

the OPPOSITE sides. A CIS double bond BENDS  the fatty acid molecule, while the somewhat  

more SYMMETRIC trans configuration does NOT.  A trans-fat is therefore similar in structure  

to a SATURATED fat. More importantly, trans-fats  RARELY occur in nature so the body does NOT have  

the necessary enzymes to break them down. Diets  rich in trans-fats INCREASE the BAD cholesterol  

LDL and REDUCE the GOOD cholesterol HDL, having  the most DETRIMENTAL effect on blood vessels. 

Trans-fats are found mainly in partially  hydrogenated oil products, such as margarine.  

Because unsaturated fats are less stable and spoil  faster, food manufacturers add hydrogens to make  

them MORE saturated through a process known as  partial hydrogenation. This process not only  

prolongs shelf-life of vegetable oils, but also  turns them into solid, or semi-solid products,  

which are preferred by commercial bakers for  their low cost and wide range of different  

textures. Unfortunately, partial hydrogenation  also CONVERTS some of the CIS double bonds into  

TRANS configuration, producing trans-fats. The  FDA has officially banned production of partially  

hydrogenated oils in June 2018, but products made  earlier may still be in use until January 2020.