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From Wikipedia, the free encyclopedia

A space-filling model of an unsaturated triglyceride.
A fat, or triglyceride, molecule. Note the three fatty acid chains attached to the central glycerol portion of the molecule.
Composition of fats from various foods, as percentage of their total fat.
Composition of fats from various foods, as percentage of their total fat.

Fat is one of the three main macronutrients, along with carbohydrate and protein.[1] Fats molecules consist of primarily carbon and hydrogen atoms, thus they are all hydrocarbon molecules. Examples include cholesterol, phospholipids and triglycerides.

The terms "lipid", "oil" and "fat" are often confused. "Lipid" is the general term, though a lipid is not necessarily a triglyceride. "Oil" normally refers to a lipid with short or unsaturated fatty acid chains that is liquid at room temperature, while "fat" (in the strict sense) specifically refers to lipids that are solids at room temperature – however, "fat" (in the broad sense) may be used in food science as a synonym for lipid. Fats, like other lipids, are generally hydrophobic, and are soluble in organic solvents and insoluble in water.

Fat is an important foodstuff for many forms of life, and fats serve both structural and metabolic functions. They are a necessary part of the diet of most heterotrophs (including humans) and are the most energy dense, thus the most efficient form of energy storage.[2]

Some fatty acids that are set free by the digestion of fats are called essential because they cannot be synthesized in the body from simpler constituents. There are two essential fatty acids (EFAs) in human nutrition: alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid).[3][4] Other lipids needed by the body can be synthesized from these and other fats. Fats and other lipids are broken down in the body by enzymes called lipases produced in the pancreas.

Fats and oils are categorized according to the number and bonding of the carbon atoms in the aliphatic chain. Fats that are saturated fats have no double bonds between the carbons in the chain. Unsaturated fats have one or more double bonded carbons in the chain. The nomenclature is based on the non-acid (non-carbonyl) end of the chain. This end is called the omega end or the n-end. Thus alpha-linolenic acid is called an omega-3 fatty acid because the 3rd carbon from that end is the first double bonded carbon in the chain counting from that end. Some oils and fats have multiple double bonds and are therefore called polyunsaturated fats. Unsaturated fats can be further divided into cis fats, which are the most common in nature, and trans fats, which are rare in nature. Unsaturated fats can be altered by reaction with hydrogen effected by a catalyst. This action, called hydrogenation, tends to break all the double bonds and makes a fully saturated fat. To make vegetable shortening, then, liquid cis-unsaturated fats such as vegetable oils are hydrogenated to produce saturated fats, which have more desirable physical properties e.g., they melt at a desirable temperature (30–40 °C), and store well, whereas polyunsaturated oils go rancid when they react with oxygen in the air. However, trans fats are generated during hydrogenation as contaminants created by an unwanted side reaction on the catalyst during partial hydrogenation.

Saturated fats can stack themselves in a closely packed arrangement, so they can solidify easily and are typically solid at room temperature. For example, animal fats tallow and lard are high in saturated fatty acid content and are solids. Olive and linseed oils on the other hand are unsaturated and liquid. Fats serve both as energy sources for the body, and as stores for energy in excess of what the body needs immediately. Each gram of fat when burned or metabolized releases about 9 food calories (37 kJ = 8.8 kcal).[4] Fats are broken down in the healthy body to release their constituents, glycerol and fatty acids. Glycerol itself can be converted to glucose by the liver and so become a source of energy.

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Transcription

Global obesity rates are on the rise, and despite popular opinion, not just in the United States. As processed foods become more popular and technology makes our lives easier and more convenient, our population is becoming heavier. While there are plenty of exercise guides out there and warnings on how to avoid gaining weight, what are some underlooked factors that might be making you lose the battle of the bulge? Welcome to another episode of The Infographics Show- These are the reasons why you are getting fat! Each year the world spends $579 billion in fast food, which is more than the entire total gross domestic product of Sweden at it speak in 2013 and 2014. In the US alone fast food sales topped at $200 billion in 2015, an incredible climb from just $6 billion in 1970. And as fast food becomes more popular around the world, these figures are only set to rise. It can be easy to look down on these figures, but the modern high-stress lifestyle often leaves individuals with little time for personal home-cooked meals- so let's look at some other factors that can help you mitigate some of the pounds you're putting on. 11. Amnesiac Eating Everyone's done it before- you get home from work and veg out on the couch to catch up on your favorite show. In the mood for a snack, you grab yourself a bag of chips and munch away as you watch, mind enraptured by the fantastic adventures on your television screen (or amazing episodes of The Infographics Show!). Suddenly you look down and before you know it, you've finished off an entire bag of chips in one sitting! Known as amnesiac eating, this is one of the most under appreciated factors in weight gain today, and with Americans spending $7.5 billion on potato chips every year, it's a widespread phenomenon. A sister symptom can be 'bored eating', where you start eating something tasty out of sheer boredom, and food has long been a refuge for those suffering from severe depression. If you find yourself overindulging an easy fix is to swap to something healthier like baby carrots, where the risk of overeating will only be too much starch and an uncomfortable bathroom trip a few hours later... 10. Not enough sleep. In a global sleep ranking study, the United States came in at tenth in quantity of sleep per night, yet another study showed that 40% of all Americans aren't getting enough sleep. You might think that being awake would lead to burning more calories, after all your body is fully switched 'on' and consuming energy- yet not getting enough sleep can lead to some seriously bad weight gain habits. If you're finding yourself sleep at work, you're more likely to reach for a cup of coffee or soda, followed by a sugary snack. And if you're at home and unable to sleep you're probably going to go for a comfort food of some sort. Not only are you picking up bad eating habits, but lack of sleep also increases your fatigue, meaning you're far more likely to skip a gym day and try to catch some Zs instead. 9. After-dinner snacks Everyone knows you can't have your dessert until after you eat your dinner, but maybe its time to start skipping dessert altogether. Though there's nothing wrong with the occasional treat, too many people are overindulging after eating, and it can be a tough habit to break given how trained our minds can be to continue bad habits. To make matters worse, American dinner plates have gotten bigger over the last few decades, which offers a poor perspective on one's dinner as a large portion looks much smaller when the plate is oversized. 8. Shopping when hungry It's an age-old adage: don't go grocery shopping when you're hungry, usually followed by another age-old adage: your eyes can be bigger than your stomach. The simple fact is that going shopping when hungry can make all the food you see at the grocery store appear delicious, and can seriously influence your shopping experience. If you're feeling hungry en route to the grocery store, grab a quick bite first, and then compare the amount- and type- of groceries you bring home when hungry and when not. We're betting the results will surprise you. 7. Me hungry now! Modern society is full of convenience, and all too often that convenience comes in the form of cheap, delicious fast food. As animals we are evolutionarily hardwired for instant gratification- in the wild extra calories are rare, and given the opportunity it's a better survival strategy to gorge now as food may not be available later. But we're no longer bound by the rules of evolution, and your impatience is going to end up costing you serious inches in the waistline. Next time you're hungry, tough it out a bit and wait till you're home and can make something healthier to eat. 6. It's just a drink... When was the last time you counted the calories in that delicious mojito you had to unwind after a tough week at work? Americans seem to have a major blind spot for alcoholic beverages and the staggering amount of calories each can contain. The average beer has 185 calories, and if you think you're safe by sticking to liquor think again- 1.5 ounces of vodka can contain 121 calories. That's the equivalent of a bite-sized chocolate bar every time you down a drink. 5. Skipping breakfast It might sound counterintuitive, but by skipping breakfast you are actually making yourself more prone to weight gain. That's because after sleeping for 8 hours (or probably less), your body has fasted and not consumed any calories. When you skip breakfast your stomach takes note and starts to rebel, demanding food. As lunch time comes around you may have planned on a salad and some fruit on the side, but your calorie starved stomach is going to demand something a lot more substantial. Don't fight your stomach- get yourself a light breakfast to keep it happy until lunch. 4. Portion distortion It's not just American dinner plates that have gotten physically bigger over the last few decades, it's the size of portions served at restaurants as well. With plummeting food prices restaurants have heaped on the servings, and with a brain that's still trained by evolution to eat everything offered to it for fear of starvation, you're probably going to chomp down everything put in front of you without a second thought. Try and get some perspective on what proper portions look like next time you go out to eat or order in, and then limit your intake. If you manage to actually pull that off, please let us know how. 3. Fat Free is not Calorie Free Advertisers are clever, unfortunately more clever than the average consumer. Many products nowadays are advertised as fat-free, while completely ignoring how many calories the product actually contains. Consumers assume that the two are completely separate entities, when in fact they are closely related. High fat means high calories, but low fat foods can still contain a lot of calories- if you don’t burn those calories off your body will simply convert them and store them as fat! Stick to low fat and low calorie foods, or simply moderate how much you consume of each. 2. Condiments, condiments, condiments! Nowadays almost every single restaurant in the world offers heaps of condiments for free. Sauces and drizzles, packets of ketchup and mayo- order takeout from your local restaurant and you're guaranteed to get a bag full of delicious to pile on top of your food. Yet all these condiments can carry some serious calories, a single packet of ketchup is 20 calories, and a packet of yummy mayo is a whopping 90 calories. All that careful work you do in watching what you order can be of absolutely no avail if you're ruining it by pouring on the condiments. 1. And the number one habit making you gain weight... is not exercising. Did you really expect any other answer? All of these bad habits can all be manageable if you maintain a good exercise routine, making a lack of exercise the number one bad habit for weight gain. So get out there, put some headphones on, throw a few Infographics Show episodes on your iphone and hit the treadmill for a few minutes a day! What's your worst weight gain habit? What's your best tip for keeping off the pounds? Let us know in the comments section below. Also, be sure to watch our other video called Why You Shouldn’t Eat At Night. Thanks for watching, and as always, don't forget to like, share and subscribe, and, as ever, see you next time!

Contents

Chemical structure

Example of a natural triglyceride with three different fatty acids. One fatty acid is saturated (blue highlighted), another contains one double bond within the carbon chain (green highlighted). The third  fatty acid (a polyunsaturated fatty acid, highlighted in red) contains three double bonds within the carbon chain. All carbon-carbon double bonds shown are cis isomers.
Example of a natural triglyceride with three different fatty acids. One fatty acid is saturated (blue highlighted), another contains one double bond within the carbon chain (green highlighted). The third fatty acid (a polyunsaturated fatty acid, highlighted in red) contains three double bonds within the carbon chain. All carbon-carbon double bonds shown are cis isomers.

There are many different kinds of fats, but each is a variation on the same chemical structure. All fats are derivatives of fatty acids and glycerol. Most fats are glycerides, particularly triglycerides (triesters of glycerol). One chain of fatty acid is bonded to each of the three -OH groups of the glycerol by the reaction of the carboxyl end of the fatty acid (-COOH) with the alcohol; I.e. three chains per molecule. Water is eliminated and the carbons are linked by an -O- bond through dehydration synthesis. This process is called esterification and fats are therefore esters. As a simple visual illustration, if the kinks and angles of these chains were straightened out, the molecule would have the shape of a capital letter E. The fatty acids would each be a horizontal line; the glycerol "backbone" would be the vertical line that joins the horizontal lines. Fats therefore have "ester" bonds.

The properties of any specific fat molecule depend on the particular fatty acids that constitute it. Fatty acids form a family of compounds that are composed of increasing numbers of carbon atoms linked into a zig-zag chain (hydrogen atoms to the side). The more carbon atoms there are in any fatty acid, the longer its chain will be. Long chains are more susceptible to intermolecular forces of attraction (in this case, van der Waals forces), and so the longer ones melt at a higher temperature (melting point).

Examples of fatty acids.
trans Unsaturated (Example shown: Elaidic acid) cis Unsaturated (Example shown: Oleic acid) Saturated (Example shown: Stearic acid)
Elaidic-acid-3D-balls.png
Oleic-acid-3D-ball-&-stick.png
Stearic-acid-3D-balls.png
Elaidic acid is the principal trans unsaturated fatty acid often found in partially hydrogenated vegetable oils. Oleic acid is a cis unsaturated fatty acid making up 55–80% of olive oil. Stearic acid is a saturated fatty acid found in animal fats and is the intended product in full hydrogenation. Stearic acid is neither cis nor trans because it has no carbon-carbon double bonds.

Fatty acid chains may also differ by length, often categorized as short to very long.

  • Short-chain fatty acids (SCFA) are fatty acids with aliphatic tails of fewer than six carbons (i.e. butyric acid).
  • Medium-chain fatty acids (MCFA) are fatty acids with aliphatic tails of 6–12 carbons, which can form medium-chain triglycerides.
  • Long-chain fatty acids (LCFA) are fatty acids with aliphatic tails of 13 to 21 carbons.
  • Very long chain fatty acids (VLCFA) are fatty acids with aliphatic tails of 22 or more carbons.

Any of these aliphatic fatty acid chains may be glycerated and the resultant fats may have tails of different lengths from very short triformin to very long, e.g., cerotic acid, or hexacosanoic acid, a 26-carbon long-chain saturated fatty acid. Long chain fats are exemplified by tallow (lard) whose chains are 17 carbons long. Most fats found in food, whether vegetable or animal, are made up of medium to long-chain fatty acids, usually of equal or nearly equal length. Many cell types can use either glucose or fatty acids for this energy. In particular, heart and skeletal muscle prefer fatty acids. Despite long-standing assertions to the contrary, fatty acids can also be used as a source of fuel for brain cells.[citation needed]

Importance for living organisms

Fats are also sources of essential fatty acids, an important dietary requirement. They provide energy as noted above. Vitamins A, D, E, and K are fat-soluble, meaning they can only be digested, absorbed, and transported in conjunction with fats. Fats play a vital role in maintaining healthy skin and hair, insulating body organs against shock, maintaining body temperature, and promoting healthy cell function. Fat also serves as a useful buffer against a host of diseases. When a particular substance, whether chemical or biotic, reaches unsafe levels in the bloodstream, the body can effectively dilute—or at least maintain equilibrium of—the offending substances by storing it in new fat tissue. This helps to protect vital organs, until such time as the offending substances can be metabolized or removed from the body by such means as excretion, urination, accidental or intentional bloodletting, sebum excretion, and hair growth.

Adipose tissue

The obese mouse on the left has large stores of adipose tissue. For comparison, a mouse with a normal amount of adipose tissue is shown on the right.
The obese mouse on the left has large stores of adipose tissue. For comparison, a mouse with a normal amount of adipose tissue is shown on the right.

In animals, adipose tissue, or fatty tissue is the body's means of storing metabolic energy over extended periods of time. Adipocytes (fat cells) store fat derived from the diet and from liver metabolism. Under energy stress these cells may degrade their stored fat to supply fatty acids and also glycerol to the circulation. These metabolic activities are regulated by several hormones (e.g., insulin, glucagon and epinephrine). Adipose tissue also secretes the hormone leptin. [5]

The location of the tissue determines its metabolic profile: visceral fat is located within the abdominal wall (i.e., beneath the wall of abdominal muscle) whereas "subcutaneous fat" is located beneath the skin (and includes fat that is located in the abdominal area beneath the skin but above the abdominal muscle wall). Visceral fat was recently discovered to be a significant producer of signaling chemicals (i.e., hormones), among which several are involved in inflammatory tissue responses. One of these is resistin which has been linked to obesity, insulin resistance, and Type 2 diabetes. This latter result is currently controversial, and there have been reputable studies supporting all sides on the issue.

Fatty acids and human health

Dietary consumption of fatty acids has effects on human health. Studies have found that replacing saturated fats with cis unsaturated fats in the diet reduces risk of cardiovascular disease. For example, a 2015 systematic review of randomized control trials by the Cochrane Library concluded: "Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturated fats."[6]

Numerous studies have also found that consumption of trans fats increases risk of cardiovascular disease.[3][4] The Harvard School of Public Health advises that replacing trans fats and saturated fats with cis monounsaturated and polyunsaturated fats is beneficial for health.[7] a 2014 meta-analyses of randomized controlled trials found that reducing fat and cholesterol intake does not effect cardiovascular disease or all cause mortality.[8]

See also

References

  1. ^ "Macronutrients: the Importance of Carbohydrate, Protein, and Fat". McKinley Health Center. University of Illinois at Urbana–Champaign. Retrieved 20 September 2014.
  2. ^ "Introduction to Energy Storage". Khan Academy.
  3. ^ a b Mozaffarian, Dariush; Katan, Martijn B.; Ascherio, Alberto; Stampfer, Meir J.; Willett, Walter C. (2006-04-13). "Trans Fatty Acids and Cardiovascular Disease". New England Journal of Medicine. 354 (15): 1601–1613. doi:10.1056/NEJMra054035. ISSN 0028-4793. PMID 16611951.
  4. ^ a b c United Kingdom The Food Labelling Regulations 1996Schedule 7: Nutrition labelling
  5. ^ "The human proteome in adipose - The Human Protein Atlas". www.proteinatlas.org. Retrieved 2017-09-12.
  6. ^ Hooper, Lee; Martin, Nicole; Abdelhamid, Asmaa; Davey Smith, George (2015). "Reduction in saturated fat intake for cardiovascular disease". Cochrane Database of Systematic Reviews (6): CD011737. doi:10.1002/14651858.CD011737. PMID 26068959.
  7. ^ "Fats and Cholesterol", Harvard School of Public Health. Retrieved 02-11-16.
  8. ^ Harcombe, Zoë; Baker, Julien S.; Cooper, Stephen Mark; Davies, Bruce; Sculthorpe, Nicholas; Dinicolantonio, James J.; Grace, Fergal (2015). "Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review and meta-analysis". Open Heart. 2: e000196. doi:10.1136/openhrt-2014-000196. PMC 4316589. PMID 25685363.

Further reading

This page was last edited on 7 April 2019, at 17:47
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