An unsaturated fat is a fat or fatty acid in which there is at least one double bond within the fatty acid chain. A fatty acid chain is monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond. Where double bonds are formed, hydrogen atoms are eliminated. Thus, a saturated fat has no double bonds, has the maximum number of hydrogens bonded to the carbons, and therefore is "saturated" with hydrogen atoms. In cellular metabolism, unsaturated fat molecules contain somewhat less energy (i.e., fewer calories) than an equivalent amount of saturated fat. The greater the degree of unsaturation in a fatty acid (i.e., the more double bonds in the fatty acid) the more vulnerable it is to lipid peroxidation (rancidity). Antioxidants can protect unsaturated fat from lipid peroxidation.
Chemistry and nutrition
Double bonds may be in either a cis or a trans isomer, depending on the geometry of the double bond. In the cis isomer, hydrogen atoms are on the same side of the double bond, whereas, in the trans isomer, they are on opposite sides (see trans fat). Saturated fats are popular with manufacturers of processed foods because they are less vulnerable to rancidity and are, in general, more solid at room temperature than unsaturated fats. Unsaturated chains have a lower melting point, hence increasing fluidity of the cell membranes.
Although both monounsaturated and polyunsaturated fats can replace saturated fat in the diet, trans unsaturated fats should be avoided. Replacing saturated fats with unsaturated fats helps to lower levels of total cholesterol and LDL cholesterol in the blood. Trans unsaturated fats are particularly risky because the double bond stereochemistry allows the fat molecules to assume a linear conformation, which leads to efficient packing (i.e., plaque formation). The geometry of the cis double bond introduces a bend in the molecule, thereby precluding stable formations (see Trans fat#Chemistry links above for drawings that illustrate this). Natural sources of fatty acids (see above) are rich in the cis isomer.
Although polyunsaturated fats are protective against cardiac arrhythmias, a study of post-menopauseal women with a relatively low fat intake showed that polyunsaturated fat is positively associated with progression of coronary atherosclerosis, whereas monounsaturated fat is not. This probably is an indication of the greater vulnerability of polyunsaturated fats to lipid peroxidation, against which vitamin E has been shown to be protective.
Examples of unsaturated fats are palmitoleic acid, oleic acid, myristoleic acid, linoleic acid, and arachidonic acid. Foods containing unsaturated fats include avocado, nuts, and vegetable oils such as canola and olive oils. Meat products contain both saturated and unsaturated fats.
Although unsaturated fats are conventionally regarded as 'healthier' than saturated fats, the United States Food and Drug Administration (FDA) recommendation stated that the amount of unsaturated fat consumed should not exceed 30% of one's daily caloric intake. Most foods contain both unsaturated and saturated fats. Marketers advertise only one or the other, depending on which one makes up the majority. Thus, various unsaturated fat vegetable oils, such as olive oils, also contain saturated fat.
In chemical analysis, fatty acids are separated by gas chromatography of methyl esters; additionally, a separation of unsaturated isomers is possible by argentation thin-layer chromatography.
Role of dietary fats in insulin resistance
Incidence of Insulin resistance is lowered with diets higher in monounsaturated fats (especially oleic acid), while the opposite is true for diets high in polyunsaturated fats (especially large amounts of arachidonic acid) as well as saturated fats (such as arachidic acid), these ratios can be indexed in the phospholipids of human skeletal muscle and in other issues as well. This relationship between dietary fats and insulin resistance is presumed secondary to the relationship between insulin resistance and inflammation, which is partially modulated by dietary fat ratios (Omega-3/6/9) with both omega 3 and 9 thought to be anti-inflammatory, and omega 6 pro-inflammatory (as well as by numerous other dietary components, particularly polyphenols, and by exercise as well, with both of these anti-inflammatory). Although both pro-inflammatory and anti-inflammatory types of fat are biologically necessary, fat dietary ratios in most US diets are skewed towards Omega 6, with subsequent disinhibition of inflammation and potentiation of insulin resistance. But this is contrary to the suggestion of more recent studies, in which polyunsaturated fats are shown as protective against insulin resistance.
Membrane composition as a metabolic pacemaker
Studies on the cell membranes of mammals and reptiles discovered that mammalian cell membranes are composed of a higher proportion of polyunsaturated fatty acids(DHA, omega-3 fatty acid) than reptiles  Studies on bird fatty acid composition have noted similar proportions to mammals but with 1/3rd less omega-3 fatty acids as compared to omega-6 for a given body size. This fatty acid composition results in a more fluid cell membrane but also one that is "leakier" to various ions (H+ & Na+), resulting in cell membranes that are more costly to maintain. This maintenance cost has been argued to be one of the key causes for the high metabolic rates and concomitant warm-bloodedness of mammals and birds. However polyunsaturation of cell membranes may also occur in response to chronic cold temperatures as well. In fish increasingly cold environments lead to increasingly high cell membrane content of both monounsaturated and polyunsaturated fatty acids, to maintain greater membrane fluidity (and functionality) at the lower temperatures.
Affects one in three adults
Affecting about 35 percent of all adults in the United States according to the CDC, metabolic syndrome contributes to weight gain, by causing a state of internal starvation called metabolic starvation. This in turn leads to increases hunger, sugar cravings and increased portions leading to overeating and weight gain.
Cause and effect misunderstood
Since we traditionally thought that the portion control (which in turn was attributed wrongly to poor will power)is the cause of weight gain, rather than the effect of this metabolic starvation, all our traditional ideas about cause and effect of obesity were not only wrong but lead to the “blame the victim” attitude when it comes to obesity.
Secret of weight gain revealed
Secret of weight gain, and metabolic syndrome revealed - it has been recently proven that metabolic syndrome, and the weight gain itself are caused by a process called insulin resistance. Check your metabolic syndrome risk using the free Metabolic syndrome meter. Watch this amazing Ted Med video that reveals the secret of weight loss - Stop blaming the victim for obesity
- Saturated fat
- List of unsaturated fatty acids
- Monounsaturated fat
- Polyunsaturated fat
- Trans fat
- Iodine number – a chemical analysis method to determine the proportion of unsaturated fat.
Calories and Nutritional Information of Foods
- Calorie Finder - Look for high protein, high fiber, and low calorie foods!!
- Nutrition Database - Comprehensive list of foods with their nutritional values & glycemic load, organized A-Z.
- Glycemic Index of Foods - Database of Glycemic index values of foods organized A-Z.
W8MD's 52 weeks of weight loss videos - cereal grains
Glossary of healthy eating | Nutritional value of foods: UK Foods | US Foods | Dietary Supplements | Nutrition values of foods Portions of content adapted from Wikipedias article on Unsaturated fat licensed under GNU FDL.
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