Fat is one of the three main macronutrients, along with the other two: carbohydrate and protein. 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) may specifically refer 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 and do not bind water thus do not increase body mass as much as proteins, especially carbohydrates, both of which bind a lot more water.
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). 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). 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.
Relatively great in extent from one surface to the opposite in its smallest solid dimension.
Measuring a certain number of units in this dimension.
“I want some planks that are two inches thick.”
Heavy in build; thickset.
“He had such a thick neck that he had to turn his body to look to the side.”
Densely crowded or packed.
“We walked through thick undergrowth.”
Having a viscous consistency.
“My mum’s gravy was thick but at least it moved about.”
Abounding in number.
“The room was thick with reporters.”
Impenetrable to sight.
“We drove through thick fog.”
Difficult to understand, or poorly articulated.
“We had difficulty understanding him with his thick accent.”
“He was as thick as two short planks.”
Friendly or intimate.
“They were as thick as thieves.”
Deep, intense, or profound.
Curvy and voluptuous, and especially having large hips.
In a thick manner.
“Snow lay thick on the ground.”
“Bread should be sliced thick to make toast.”
Frequently; in great numbers.
“The arrows flew thick and fast around us.”
The thickest, or most active or intense, part of something.
“It was mayhem in the thick of battle.”
A stupid person; a fool.
Carrying more fat than usual on one’s body; plump; not lean or thin.
“The fat man had trouble getting through the door.”
“The fattest pig should yield the most meat.”
“The fat wallets of the men from the city brought joy to the peddlers.”
Oily; greasy; unctuous; rich; said of food.
Exhibiting the qualities of a fat animal; coarse; heavy; gross; dull; stupid.
“a fat soil;”
“a fat pasture”
Rich; producing a large income; desirable.
“a fat benefice;”
“a fat office;”
“a fat job”
Abounding in riches; affluent; fortunate.
Of a character which enables the compositor to make large wages; said of matter containing blank, cuts, or many leads, etc.
“a fat take;”
“a fat page”
alternative form of phat
A specialized animal tissue with a high oil content, used for long-term storage of energy.
A refined substance chemically resembling the oils in animal fat.
That part of an organization deemed wasteful.
“We need to trim the fat in this company”
“I saw Daniel crack a fat.”
A poorly played shot where the ball is struck by the top part of the club head. (see also thin, shank, toe)
The best or richest productions; the best part.
“to live on the fat of the land”
Work containing much blank, or its equivalent, and therefore profitable to the compositor.
A large tub or vessel for water, wine, or other liquids; a cistern.
A dry measure, generally equal to nine bushels.
To make fat; to fatten.
“kill the fatted calf”
To become fat; to fatten.
with opposite sides or surfaces that are far or relatively far apart
“the walls are 5 feet thick”
“thick slices of bread”
“thick metal cables”
(of a garment or other knitted or woven item) made of heavy material
“a thick sweater”
(of writing or printing) consisting of broad lines
“a headline in thick black type”
made up of a large number of things or people close together
“the road winds through thick forest”
“his hair was long and thick”
densely filled or covered with
“the air was thick with tension”
“the ground was thick with yellow leaves”
(of the air or atmosphere, or a substance in the air) opaque, dense, or heavy
“a motorway pile-up in thick fog”
“a thick cloud of smoke”
(of a person’s head) having a dull pain or heavy feeling, especially as a result of a hangover or illness
“influenza can cause a thick head”
“Stephen woke late, his head thick and his mouth sour”
(of a liquid or a semi-liquid substance) relatively firm in consistency; not flowing freely
of low intelligence; stupid
“he’s a bit thick”
(of a voice) not clear or distinct; hoarse or husky
“Guy’s voice was thick with desire”
“a snarling thick voice”
(of an accent) very marked and difficult to understand
“a thick French accent”
having a very close, friendly relationship
“he’s very thick with the new master”
the most active or crowded part of something
“we were in the thick of the battle”
in or with deep, dense, or heavy mass
“bread spread thick with butter”
a natural oily substance occurring in animal bodies, especially when deposited as a layer under the skin or around certain organs
“whales and seals insulate themselves with layers of fat”
a fatty substance made from animal or plant products, used in cooking
“a diet high in animal fats”
the presence of excess fat in a person or animal
“he was a tall man, running to fat”
any of a group of natural esters of glycerol and various fatty acids, which are solid at room temperature and are the main constituents of animal and vegetable fat
“some 40 per cent of our daily calories are derived from dietary fats”
(of a person or animal) having a large amount of excess flesh
“the driver was a fat wheezing man”
(of an animal bred for food) made plump for slaughter.
containing much fat
(of coal) containing a high proportion of volatile oils.
large in bulk or circumference
“a fat cigarette”
(especially in the context of financial reward) substantial
“a fat profit”
“a fat cheque”
used ironically to express the belief that something is unlikely or does not exist
“fat chance she had of influencing Guy’s decisions”
make or become fat
“the hogs have been fatting”
“numbers of black cattle are fatted here”