Obesity Education Initiative. National Heart Lung and
Blood Institute. P.O. Box 30105, Bethesda, MD 20824-Margaret Alic, Ph.D.Fats
Definition
Fats are also known as lipids. A lipid is a sub-
stance that is poorly soluble or insoluble inwater. The
term ‘dietary fat’ encompasses many different types of
fat. Over 90% of dietary fats are called triacylglycerols
ortriglycerides. Other dietary fats include cholesterol.
Triacylglycerols contain three fatty acids attached
to a glycerol molecule. Fatty acids vary according to
their length, which is composed of carbon and hydro-
gen atoms joined together to form a hydrocarbon
chain. The number of double bonds that occur
between the carbon molecules also varies. The chem-
ical structure of each type of fatty acid determines its
physical characteristics and its nutritional and physio-
logical function. Regardless of the type of fatty acid
present, all triacylglycerols provide 9 kcal (37 KJ) per
gram; this makes fat the most concentrated source of
energy in the diet. Fatty acids should provide no more
than 30–35% of dietary energy or approximately no
more than 70 g a day for women and no more than 90 g
a day for men.
Typical high sources of fat in the diet include
cooking fats and oils, fried food, fatty and processed
meats. These should form a very small part of the diet.
Care should be taken to reduce fried foods; avoid
adding fats and oils during cooking; to grill food,
which allows fat to drip out; and to choose lean
meats and low fat dairy products. A product is
thought to be low in fat if it contains less than 3 g fat
per 100 g and high in fat if it contains more than 20 g
fat per 100 g or 21 g fat per serving.Purpose
Some types of fatty acids are essential nutrients.
They must be consumed in the diet for the body to
function properly. Fats form the structure of cell mem-
branes, they are involved in the transport, breakdown
and excretion of cholesterol and they are the building
blocks for many important compounds such as hor-
mones, blood clotting agents, and compounds involved
in immune and inflammatory responses. Fats alsotransport fat solublevitaminsandantioxidants;pro-
vide the body with insulation and form a protective
layer around organs; are a structural component of
the brain and nervous system; and provide a reserve
supply of energy in the form of adipose tissue (body
fat). Excess amounts of adipose tissue definesobesity
and may lead to health problems such as diabetes,
cancerand heart disease.Description
Saturated fatty acids
Saturated fatty acids have a hydrocarbon chain
where each carbon atom carries its maximum number
of hydrogen atoms except for the end carboxyl group
and they do not have any double bonds. The molecules
are straight, allowing them to pack closely together.
For this reason, they are solid at room temperature
with a high melting point. Saturated fatty acids are
chemically stable both within the body and in food.
Saturated fatty acids are named according to the
number of carbon atoms they contain. Each one has a
common name (e.g., stearic acid), a systematic name
(e.g., octadecanoic acid because stearic acid has 18
carbon atoms), and a notational name (e.g., 18:0 as
stearic acid has 18 carbon atoms but no double
bonds).
Animal products such as meat fat, dripping, lard,
milk, butter, cheese and cream are the primary sources
of saturated fatty acids. Most plant products have a
lower amount of saturated fat with the exception of
coconut and palm oil.
SATURATED FATTY ACIDS AND HEALTH.Saturated
fatty acids increase the body’s levels of cholesterol,
including low density lipoprotein (LDL) cholesterol.
LDL cholesterol is commonly known as ‘bad’ choles-
terol. High levels of LDL cholesterol in the blood
increase the risk of cardiovascular disease. LDL cho-
lesterol transports excess cholesterol through the
bloodstream where it can become deposited in the
walls of the arteries and form a hardened plaque.
This is called atherosclerosis. This thickening of the
artery walls reduces the flow of blood supplying the
heart, brain, and other organs. A heart attack or
stroke is caused by a blood clot blocking these nar-
rowed arteries. Saturated fatty acids also contribute to
production of these blood clots as they are converted
into substances that can increase the stickiness of the
blood and increase its tendency to clot. For this reason
dietary guidelinesrecommend that no more than 10%
of dietary energy should come from saturated fatty
acids. This means that on a daily basis approximately
no more than 22 g saturated fat should be consumedFats