Unrefined and refined carbohydrates
Apart from potatoes, all the foods listed in this group began life as a
grain, such as wheat, rye, corn, rice or barley. Potatoes and grains are
very healthy and filling; however, you can be even healthier if you choose
unrefined versions of these foods over refined versions.

Top tip
If you decide to increase the amount of fibre you eat, try to drink more
water too. Your body doesn't digest fibre, so you need the extra water to
help it flow through your digestive system with ease.

Refined carbohydrates refers to foods where machinery has been used to
remove the high fibre bits (the bran and the germ) from the grain. White
rice, white bread, sugary cereals, and pasta and noodles made from white
flour are all examples of refined carbohydrates.

Unrefined carbohydrates still contain the whole grain, including the bran
and the germ, so they're higher in fibre and will keep you feeling fuller
for longer - great if you're trying to lose weight and hate feeling hungry.
Examples include wholegrain rice, wholemeal bread, porridge oats and
wholewheat pasta.

If you'd like to eat more fibre or beat hunger pangs, try these healthy
swaps:

 

Refined Swap Unrefined
Frosted flakes  Bran flakes
White toast  Porridge oats
Cereal bar  Rice cakes
French bread  Wholemeal bread
Normal pasta  Wholewheat pasta
Breadstick  Dark rye crispbread

 

Simple and complex carbohydrates
These are often confused with refined and unrefined carbohydrates, but the
terms simple and complex refer to how complicated the chemical structure of
a carbohydrate is rather than to whether it's wholegrain or not. Complex
carbohydrates are the most common and there are three kinds:

Glycogen. This is your body's major fuel source and is sometimes referred to
as blood sugar. It's formed from glucose, which is found in almost all
foods, and is converted into energy.

Starch. This is only found in plants and, contrary to popular belief, isn't
fattening (it's the rich sauces, fats and oils often added to pasta,
potatoes, rice, noodles and bread that are the culprits!).

Fibre (non-starch polysaccharide). This is abundant in unrefined
carbohydrates, fruit and vegetables, and is important because it helps your
body to process waste efficiently and helps you to feel fuller for longer.

Did you know...?

On average, you have the equivalent of four teaspoons of sugar circulating
in your bloodstream.
With food-refining machinery came the invention of white bread. At the time,
it was considered to be an enormous luxury that only the very rich could
afford to eat.

How much is enough?
Nutritionists recommend that the bread, cereals and potatoes group makes up
the bulk of your diet - roughly 47 to 50 per cent. They also suggest that
your dietary intake includes 18g of fibre every day.

An easy way to do this is to make sure that a food from this group forms the
basis of every meal - and opt for fibre-rich unrefined carbohydrates. Here
are some healthy ideas to get you started:

porridge oats with natural yoghurt, raisins and sunflower seeds for
breakfast
wholemeal bread banana sandwich or jacket potato and chilli for lunch
seafood paella, made with brown rice, for dinner

Proteins

Meat, fish, eggs and alternatives
Maxine Stinton

This food group includes poultry, pulses, beans, nuts, seeds, soya products
and vegetable protein foods such as quorn and seitan. They're grouped
together because they're all rich in protein.

 

In this article

Types of protein
Advice for vegans and vegetarians
How much is enough?

 

Types of protein
Protein plays an essential role in building and repairing your body. But
whether it helps a fingernail to grow or heals a sore muscle, for example,
depends on the make-up of the protein.

Proteins consist of smaller units called amino acids, which can link
together in many combinations to form chains. Some amino acid chains are
created by your body, but those called essential amino acids must come from
your diet. Although all animal and plant cells contain some protein, the
amount and the quality of the protein varies a lot.

High biological value foods contain enough indispensable amino acids for an
adult diet and are considered to be good quality protein. Meat, fish and
eggs sit in this category.

Low biological value foods don't contain enough indispensable amino acids.
Plant foods, such as pulses, nuts and seeds, are in this group.

This means that if you're vegetarian or vegan, you need to do some clever
combining of proteins at meal times to ensure that the amino acid of one
protein (eg, soya milk) can compensate for the deficiencies of another (eg,
muesli with nuts and seeds).

Advice for vegans and vegetarians
Because plant foods only contain some but not all the protein elements
needed by your body, they need to be mixed together to ensure your good
health.

Vegetarians
Foods such as eggs, nuts, seeds, beans, pulses, vegetable protein foods and
soya products all contain protein. There are also small amounts in grains
and dairy products. It's quite easy to combine two or three of these to make
sure you're getting enough protein. Here are some ideas for tasty
combinations:

Bran flakes with milk and sunflower seeds (grain + dairy product + seed).
Grated cheese and baked beans on toast (dairy product + bean + grain).
Egg fried rice with chick peas (grain + egg + pulse).
Yoghurt dip with aubergine curry and naan (dairy product + grain).
Vegans
If you're vegan and don't eat dairy products or eggs, there's no reason to
feel limited. Here are some ideas:

Muesli with nuts, seeds and soya milk (nut + grain + seed + soya).
Tomato and lentil soup with bread (pulse + grain).
Stir-fried tofu, vegetables and rice (tofu + grain).

Did you know...?
Eggs contain all eight essential amino acids, making them a perfect source
of protein. However, you'd have to eat at least eight eggs a day to get all
the protein you need. Be sensible; include them as part of a balanced and
varied diet.

How much is enough?
Health professionals recommend that protein makes up 10 to 15 per cent of
your diet. They suggest that adult males eat 55.5g protein every day and
adult females eat 45g. In real terms, eating a moderate amount of protein -
in one or two meals every day - should give you all the protein you need.

The need to eat protein daily is worth emphasising because your body can't
store it - you can't stock up on it by bingeing on protein once a week, for
example.

fruit and vegetables
Fruit and vegetables
Maxine Stinton

Fruit and vegetables are brimming with fibre, plus a whole range of vitamins
and minerals, and because they're low in calories, they make an important
and healthy addition to any diet.

 

In this article

Five a day
How much is a portion?
Vitamins
Fat-soluble vitamins
Water-soluble vitamins
Minerals
Major minerals
Trace minerals

 

Five a day
Scientific studies have shown that people who eat a lot of fruit and
vegetables may have a lower risk of getting illnesses, such as heart disease
and some cancers. For this reason, health authorities recommend that you eat
at least five portions of fruit and vegetables every day - and it doesn't
matter whether they're fresh, tinned, frozen, cooked, juiced or dried.

How much is a portion?
One piece of medium-sized fruit - eg, an apple, peach, banana or orange.
One slice of large fruit, such as melon, mango or pineapple.
One handful of grapes or two handfuls of cherries or berry fruits.
One tablespoon of dried fruit.
A glass (roughly 100ml) of fruit or vegetable juice.
A small tin (roughly 200g) of fruit.
A side salad.
A serving (roughly 100g) of vegetables - eg, frozen or mushy peas, boiled
carrots or stir-fried broccoli.
The vegetables served in a portion of vegetable curry, lasagne, stir-fry or
casserole.

Top tip
Next time you're shopping, buy one new fruit or vegetable you've never tried
before or didn't like as a child. Tastes change and by exploring new foods
you'll be giving your tastebuds a treat and doing your body a favour.

So how does this advice translate to real life? How do you make sure that
you get your five portions a day? Here's some ideas:

Glass of pink grapefruit juice for breakfast = 1 portion.
Small pack of dried apricots for mid-morning snack, instead of a chocolate
bar or bag of crisps = 1 portion.
Side salad with lunch = 1 portion.
Sugar snap peas and asparagus, served with main meal = 1 portion.
Strawberries with dessert = 1 portion.

Milk and Dairy
Milk and dairy
Maxine Stinton

This food group includes milk, cheese, yoghurt and fromage frais - but not
butter, margarine or cream, which belong in the fat and sugar group. The
foods in this group contain many different types of nutrients but are
particularly rich in calcium.

 

In this article

The importance of calcium
Calcium for vegans and the lactose intolerant
How much is enough?

 

The importance of calcium
Calcium is a mineral that strengthens your bones and teeth and makes sure
that everything runs smoothly with your muscles and nerves. It's especially
important for growth. Calcium can continue to add to the strength of your
bones until you reach the age of 30-35, when peak bone mass is reached.

After this point, as a natural part of the ageing process, your bones lose
their density and grow weaker. If you haven't had enough calcium in your
diet prior to this, there's an increased risk that your bones won't be
strong enough to cope with any weakening, which can result in the brittle
bone disease, osteoporosis.

Health professionals estimate that one in three women and one in ten men
suffer from osteoporosis, and there's concern that the diets of teenage
girls and young women, in particular, aren't high enough in calcium. Some
experts predict that the future could bring an osteoporosis epidemic in
women.

Calcium for vegans and the lactose intolerant
Of course, if your diet excludes milk and dairy products or if you can't
tolerate the milk sugar lactose, then you need to look for calcium
alternatives. You can keep your bones healthy by:

buying soya milks, yoghurts and cheeses enriched with calcium
eating lots of dark green leafy vegetables, such as spinach, broccoli and
watercress
using almonds or sesame seeds as topping on salads, cereals or desserts
snacking on dried fruits - apricots, dates and figs all contain small
amounts of calcium
if you're not vegan, adding sardines, prawns or anchovies to a main meal
How much is enough?
The Department of Health recommends that both men and women get 700mg of
calcium every day to ensure good health. Realistically, this means one of
the following:

a pint of milk
two small tubs of plain or fruit yoghurt
roughly 80g of hard cheese
The good news is, if you're concerned about your weight, getting the calcium
you need doesn't have to mean eating or drinking full-fat foods. There's
exactly the same amount of calcium in skimmed milk as there is in whole
milk. The same goes for low-fat yoghurt and reduced-fat cheese. You don't
have to buy their full-fat counterparts to look after your bones.

fats and sugars
Fats and sugars
Maxine Stinton

The foods in this group are best eaten sparingly because, although an energy
source, they contain few nutrients. Don't be fooled into thinking they're
entirely 'bad', though. Fat is an important contributor to good health.

 

In this article

Fat facts
Saturated and unsaturated
Sugary foods
How much is enough?

 

Fat facts
Fat transports fat-soluble vitamins A, D, E and K through your body.
It cushions your internal organs.
It makes food taste nicer.
It can contain essential fatty acids (EFAs), which are thought to have a
positive effect on the health of your heart and immune system.
It's a concentrated source of energy.
It's this last point that has given fat such a bad reputation. Just 1g of
fat provides 9 calories - more than double the calories in 1g of protein or
carbohydrate. This means if you eat a lot of fatty foods, you're likely to
put on weight. However, understanding the difference between unsaturated and
saturated fats can help.

Saturated and unsaturated
Fat can be divided into two groups - saturated and unsaturated.

Saturated fat is generally solid at room temperature and is usually from
animal sources. It's found in lard, butter, hard margarine, cheese, whole
milk and anything that contains these ingredients, such as cakes, chocolate,
biscuits, pies and pastries. It's also the white fat you can see on red meat
and underneath poultry skin. The less saturated fat you eat, the better - a
high intake has been linked with an increased risk of coronary heart
disease.

Unsaturated fat is usually liquid at room temperature and generally comes
from vegetable sources. Monounsaturated and polyunsaturated fats are both
included in this group. Unsaturated fat is a healthier alternative to
saturated fat and can be found in vegetable oils such as sesame, sunflower,
soya and olive; oily fish, such as mackerel, sardines, pilchards and salmon;
and soft margarine.

Did you know...?
In reality, many foods contain both saturated and unsaturated fats, but
they're described as one or the other depending on which makes up the
majority. So, a healthier unsaturated fat such as olive oil contains
saturated fats, too.

Sugary foods
Like fat, sugar is a concentrated source of energy and also has a bad
reputation. The psychological benefits of eating foods such as jam, sweets,
cakes, chocolate, soft drinks, biscuits and ice cream are fairly obvious.
They taste lovely and feel like a special treat. However, it's important to
keep them as just that - an occasional, special treat. Why? Because...

Sugary foods often go hand in hand with fatty foods. Think cakes, biscuits,
chocolate and pies.
Sugar interacts with the plaque on your teeth and has been proven to cause
tooth decay.
How much is enough?
Government guidelines recommend that fats make up no more than 35 per cent
of your diet. For the average woman, this means about 76g of fat per day;
for men, roughly 100g. In reality, though, most of us have much higher fat
intakes.

Ideally, we should only eat sugary foods sparingly. If you'd like to cut
down on fatty and sugary foods, follow these suggestions:

Snack on fresh or dried fruit rather than biscuits and chocolate.
Trim any visible fat off meat and poultry.
Buy lean cuts of meat and reduced-fat minces.
Ditch the frying pan - try poaching, steaming, grilling and baking instead.
Swap whole milk for semi-skimmed or skimmed alternatives.
If you use lard, butter or hard margarine, switch to vegetable oil and
low-fat spreads.

 

Think about some of the things you have eaten today -- maybe cereal, bread,
milk, juice, ham, cheese, an apple, potatoes... All of these foods (and
pretty much any other food that you can think of) contain seven basic
components:
Carbohydrates (simple and complex)
Proteins
Fats
Vitamins
Minerals
Fiber
Water
Your body's goal is to digest food and use it to keep your body alive. In
the following sections, we will look at each of these basic components to
understand what they really do and why they are so important to your body.
(Note that there might be a few non-food things mixed in with what you eat,
especially if you are eating lots of processed foods. Things like artificial
colors and chemical preservatives are the most common. Those are additives,
not part of the natural foods.)

Carbohydrates

You have probably heard of "carbohydrates" and "complex carbohydrates."
Carbohydrates provide your body with its basic fuel. Your body thinks about
carbohydrates like a car engine thinks about gasoline.
The simplest carbohydrate is glucose. Glucose, also called "blood sugar" and
"dextrose," flows in the bloodstream so that it is available to every cell
in your body. Your cells absorb glucose and convert it into energy to drive
the cell. Specifically, a set of chemical reactions on glucose creates ATP
(adenosine triphosphate), and a phosphate bond in ATP powers most of the
machinery in any human cell. If you drink a solution of water and glucose,
the glucose passes directly from your digestive system into the bloodstream.

The word "carbohydrate" comes from the fact that glucose is made up of
carbon and water. The chemical formula for glucose is: C6H12O6

You can see that glucose is made of six carbon atoms (carbo...) and the
elements of six water molecules (...hydrate). Glucose is a simple sugar,
meaning that to our tongues it tastes sweet. There are other simple sugars
that you have probably heard of. Fructose is the main sugar in fruits.
Fructose has the same chemical formula as glucose (C6H12O6), but the atoms
are arranged slightly differently. The liver converts fructose to glucose.
Sucrose, also known as "white sugar" or "table sugar," is made of one
glucose and one fructose molecule bonded together. Lactose (the sugar found
in milk) is made of one glucose and one galactose molecule bonded together.
Galactose, like fructose, has the same chemical components as glucose but
the atoms are arranged differently. The liver also converts galactose to
glucose. Maltose, the sugar found in malt, is made from two glucose atoms
bonded together.

Glucose, fructose and galactose are monosaccharides and are the only
carbohydrates that can be absorbed into the bloodstream through the
intestinal lining. Lactose, sucrose and maltose are disaccharides (they
contain two monosaccharides) and are easily converted to their
monosaccharide bases by enzymes in the digestive tract. Monosaccharides and
disaccharides are called simple carbohydrates. They are also sugars -- they
all taste sweet. They all digest quickly and enter the bloodstream quickly.
When you look at a "Nutrition Facts" label on a food package and see
"Sugars" under the "Carbohydrates" section of the label, these simple sugars
are what the label is talking about.

There are also complex carbohydrates, commonly known as "starches." A
complex carbohydrate is made up of chains of glucose molecules. Starches are
the way plants store energy -- plants produce glucose and chain the glucose
molecules together to form starch. Most grains (wheat, corn, oats, rice) and
things like potatoes and plantains are high in starch. Your digestive system
breaks a complex carbohydrate (starch) back down into its component glucose
molecules so that the glucose can enter your bloodstream. It takes a lot
longer to break down a starch, however. If you drink a can of soda full of
sugar, glucose will enter the bloodstream at a rate of something like 30
calories per minute. A complex carbohydrate is digested more slowly, so
glucose enters the bloodstream at a rate of only 2 calories per minute
(reference).

You may have heard that eating complex carbohydrates is a good thing, and
that eating sugar is a bad thing. You may even have felt this in your own
body. The following quote from The Yale Guide to Children's Nutrition
explains why:

If complex carbohydrates are broken down to monosaccharides in the
intestines before they are absorbed into the bloodstream, why are they
better than refined sugar or other di- or mono-saccharides? To a great
extent it has to do with the processes of digestion and absorption. Simple
sugars require little digestion, and when a child eats a sweet food, such as
a candy bar or a can of soda, the glucose level of the blood rises rapidly.
In response, the pancreas secretes a large amount of insulin to keep blood
glucose levels from rising too high. This large insulin response in turn
tends to make the blood sugar fall to levels that are too low 3 to 5 hours
after the candy bar or can of soda has been consumed. This tendency of blood
glucose levels to fall may then lead to an adrenaline surge, which in turn
can cause nervousness and irritability... The same roller-coaster ride of
glucose and hormone levels is not experienced after eating complex
carbohydrates or after eating a balanced meal because the digestion and
absorption processes are much slower.
If you think about it, this is incredibly interesting because it shows that
the foods you eat and the way you eat them can affect your mood and your
temperament. Foods do that by affecting the levels of different hormones in
your bloodstream over time.

Another interesting thing about this quote is its mention of insulin. It
turns out that insulin is incredibly important to the way the body uses the
glucose that foods provide. The functions of insulin are:

To enable glucose to be transported across cell membranes
To convert glucose into glycogen for storage in the liver and muscles
To help excess glucose be converted into fat
To prevent protein breakdown for energy
According to the Encyclopedia Britannica:
Insulin is a simple protein in which two polypeptide chains of amino acids
are joined by disulfide linkages. Insulin helps transfer glucose into cells
so that they can oxidize the glucose to produce energy for the body. In
adipose (fat) tissue, insulin facilitates the storage of glucose and its
conversion to fatty acids. Insulin also slows the breakdown of fatty acids.
In muscle it promotes the uptake of amino acids for making proteins. In the
liver it helps convert glucose into glycogen (the storage carbohydrate of
animals) and it decreases gluconeogenesis (the formation of glucose from
noncarbohydrate sources). The action of insulin is opposed by glucagon,
another pancreatic hormone, and by epinephrine.
What you can begin to see from this description is that there are actually
lots of different things happening in your body around glucose. Because
glucose is the essential energy source for your body, your body has many
different mechanisms to ensure that the right level of glucose is flowing in
the bloodstream. For example, your body stores glucose in your liver (as
glycogen) and can also convert protein to glucose if necessary.
Carbohydrates provide the energy that cells need to survive.

Proteins

A protein is any chain of amino acids. An amino acid is a small molecule
that acts as the building block of any cell. Carbohydrates provide cells
with energy, while amino acids provide cells with the building material they
need to grow and maintain their structure. Your body is about 20-percent
protein by weight. It is about 60-percent water. Most of the rest of your
body is composed of minerals (for example, calcium in your bones). Amino
acids are called "amino acids" because they all contain an amino group (NH2)
and a carboxyl group (COOH), which is acidic. Below you can see the chemical
structure of two of the amino acids.

You can see that the top part of each is identical to the other. That is
true of all amino acids -- the little chain at the bottom (the H or the CH3
in these two amino acids) is the only thing varying from one amino acid to
the next. In some amino acids, the variable part can be quite large. The
human body is constructed of 20 different amino acids (there are perhaps 100
different amino acids available in nature).

As far as your body is concerned, there are two different types of amino
acids: essential and non-essential. Non-essential amino acids are amino
acids that your body can create out of other chemicals found in your body.
Essential amino acids cannot be created, and therefore the only way to get
them is through food. Here are the different amino acids:

Non-essential

Alanine (synthesized from pyruvic acid)
Arginine (synthesized from glutamic acid)
Asparagine (synthesized from aspartic acid)
Aspartic Acid (synthesized from oxaloacetic acid)
Cysteine
Glutamic Acid (synthesized from oxoglutaric acid)
Glutamine (synthesized from glutamic acid)
Glycine (synthesized from serine and threonine)
Proline (synthesized from glutamic acid)
Serine (synthesized from glucose)
Tryosine (synthesized from phenylalanine)
Essential
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
Protein in our diets comes from both animal and vegetable sources. Most
animal sources (meat, milk, eggs) provide what's called "complete protein,"
meaning that they contain all of the essential amino acids. Vegetable
sources usually are low on or missing certain essential amino acids. For
example, rice is low in isoleucine and lysine. However, different vegetable
sources are deficient in different amino acids, and by combining different
foods you can get all of the essential amino acids throughout the course of
the day. Some vegetable sources contain quite a bit of protein -- things
like nuts, beans, soybeans, etc. are all high in protein. By combining them
you can get complete coverage of all essential amino acids.
The digestive system breaks all proteins down into their amino acids so that
they can enter the bloodstream. Cells then use the amino acids as building
blocks.

Nutritional label from a can of tuna fish

From this discussion you can see that your body cannot survive strictly on
carbohydrates. You must have protein. According to this article, the RDA
(Recommended Daily Allowance) for protein is 0.36 grams of protein per pound
of body weight. So a 150-pound person needs 54 grams of protein per day. The
photo above is the Nutritional Facts label from a can of tuna. You can see
that a can of tuna contains about 32 grams of protein (this can has 13 grams
per serving and there are 2.5 servings in the can). A glass of milk contains
about 8 grams of protein. A slice of bread might contain 2 or 3 grams of
protein. You can see that it is not that hard to meet the RDA for protein
with a normal diet.

Fats

We all know about the common fats that different foods contain. Meat
contains animal fat. Most breads and pastries contain vegetable oils,
shortening or lard. Deep fried foods are cooked in heated oils. Fats are
greasy and slick.

Nutritional label from a bottle of olive oil

You commonly hear about two kinds of fats: saturated and unsaturated.
Saturated fats are normally solid at room temperature, while unsaturated
fats are liquid at room temperature. Vegetable oils are the best examples of
unsaturated fats, while lard and shortening (along with the animal fat you
see in raw meat) are saturated fats. However, most fats contain a mixture.
For example, above you see the label from a bottle of olive oil. It contains
both saturated and unsaturated fats, but the saturated fats are dissolved in
the unsaturated fats. To separate them, you can put olive oil in the
refrigerator. The saturated fats will solidify and the unsaturated fats will
remain liquid. You can see that the olive oil bottler even chose to further
distinguish the unsaturated fats between polyunsaturated and
monounsaturated. Unsaturated fats are currently thought to be more healthy
than saturated fats, and monounsaturated fats (as found in olive oil and
peanut oil) are thought to be healthier than polyunsaturated fats.

Fats that you eat enter the digestive system and meet with an enzyme called
lipase. Lipase breaks the fat into its parts: glycerol and fatty acids.
These components are then reassembled into triglycerides for transport in
the bloodstream. Muscle cells and fat (adipose) cells absorb the
triglycerides either to store them or to burn them as fuel.

You need to eat fat for several reasons:

As we will see in the next section, certain vitamins are fat soluble. The
only way to get these vitamins is to eat fat.
In the same way that there are essential amino acids, there are essential
fatty acids (for example, linoleic acid is used to build cell membranes).
You must obtain these fatty acids from food you eat because your body has no
way to make them.
Fat turns out to be a good source of energy. Fat contains twice as many
calories per gram as do carbohydrates or proteins. Your body can burn fat as
fuel when necessary.
Calories

A calorie is a measurement of energy. We tend to associate calories with
food, but any sort of energy can be measured in calories. The official
definition of a calorie is the amount of energy needed to raise the
temperature of a gram of water by 1 degree C. A kilocalorie is 1,000
calories. Just to make life confusing, the "calorie" that you see on
packages of food is really a "kilocalorie" in the scientific sense.
It makes sense that food contains energy, because most foods burn. For
example, if you have ever roasted marshmallows, you probably know that
marshmallows burn. What's burning in that case is the sugar in the
marshmallow. Fat burns too -- you know that if you have ever seen a grease
fire. Your body "burns" fats, carbohydrates and proteins -- not with flames,
but with more controlled chemical reactions that release the energy in
different ways.

Fats, proteins and carbohydrates have characteristic calorie measurements.
One gram of fat contains almost 9 calories (kilocalories) of energy. One
gram of any carbohydrate contains 4 calories (kilocalories). One gram of
protein contains 4 calories (kilocalories) as well. Knowing these values,
you can calculate the number of calories in any food as long as you know how
many grams of fat, protein and carbohydrates it contains. If you were to
take any food, dry it out and burn it, the specified number of calories
would be released by the flames.

If you ingest 3,500 extra calories one day (or over the course of several
weeks or months), your body will convert the excess energy to body fat and
save it for a rainy day. To lose 1 pound of fat, therefore, you have to burn
off the 3,500 excess calories. You can do that either by exercising or by
restricting your calorie intake.

The USDA estimates that the average man, 5 feet 10 inches tall and weighing
174 pounds, needs 2,900 calories per day (assuming light to moderate
activity). The average woman, 5 feet 4 inches tall and weighing 138 pounds,
needs 2,200 calories. See this page to find out how to calculate your body's
exact calorie needs.

Between the food commercials you see on TV every day and the many nutrition
bulletins and reports you hear about on the news every night, you get a huge
amount of information about the fats that you eat. For example, you have
probably heard of the following terms:
Saturated fat
Unsaturated fat
Polyunsaturated fat
Mono-unsaturated fat
Fatty acids
Essential fatty acids
Trans fatty acids
Omega-3 and omega-6 fatty acids
Partially hydrogenated fat
Have you ever wondered what it all means, or why it matters? Why can't we
just eat, drink and be merry? In this article, you'll find out exactly what
these terms mean and how the various forms of fat you find in foods affect
your body.

What is Fat?

Corn Oil
With some grains and nuts it is very easy to see where the oil comes from.
For example, if you squeeze a sesame seed or a sunflower seed between two
sheets of paper, you can see the oil. Corn isn't quite that oily, but it
does contain oil. A kernel of corn has an outer husk surrounding a white or
yellow starchy substance. At the core of the starchy substance and toward
the pointy end of the kernel is the germ. The germ contains a small amount
of oil. If you cut a popcorn kernel in half, you can see the husk, starch
and germ. If you cut out the tiny piece of germ and squeeze the germ on a
piece of paper, you will see the oil!
We see pure fats in three places at the grocery store:
In the vegetable oil aisle you see oils created from different seeds and
nuts. There is corn oil, safflower oil, peanut oil, canola oil, olive oil...
All seeds and nuts contain some amount of oil, because oil is a very good
way to store energy. By the way, the only difference between oil and fat is
whether or not it is a solid at room temperature.
In the meat aisle, you can look at different cuts of meat and see them
outlined by a layer of white, solid fat created by the animal to store
energy.
In the dairy aisle you see butter and margarine -- fat made from cream or
vegetable oils, respectively.
The rest of the grocery store is, of course, filled with fats and oils,
although they are less obvious. Potato chips and french fries are cooked in
oil, cookies and cakes contain fats and oils, and so on. This is how we come
to eat the fat we need every day. And we do need fat - as you will learn
below, there are certain fats that we must have to survive.
So what are these fats and oils really made of? Well, if you really want to
understand fat you need to study a little bit of chemistry. To talk about
fat, we need to start by talking about fatty acids.

A fatty acid is a long hydrocarbon chain capped by a carboxyl group (COOH).
There are many common fatty acids that you hear about, four of which are
shown below along with acetic acid for comparison:

The COOH cap is what makes these molecules acids. You are probably familiar
with acetic acid because this is the acid found in vinegar. You can see that
the fatty acids are like acetic acid, but they have much longer carbon
chains.

To make a normal fat, you take three fatty acids and bond them together with
glycerol to form a triglyceride, like this:

Since this particular triglyceride happens to contain three molecules of
stearic acid, it is also known as tristearin. This diagram shows one fat
molecule. When you eat fat, you are eating collections of molecules like
these. The choice of the fatty acids in the fat controls many different
things about the fat, including how it looks, whether it is a solid or a
liquid at room temperature and how healthy it is for your body.

Saturated vs. Unsaturated

If you look at palmitic acid and stearic acid in the first figure, you can
see that the carbon chains are completely and evenly filled with hydrogen
atoms. In other words, the chains are saturated with hydrogen. Fats
(triglycerides) that contain palmitic acid and stearic acid are therefore
known as saturated fats. Fats made up of saturated fatty acids are solid at
room temperature.
In the first figure, you can see that oleic acid is not saturated. Two of
the carbons are connected by a double bond, and two of the hydrogens are
missing. This fatty acid is unsaturated. Fats that have a lot of oleic acid
in them are liquid at room temperature, and are therefore known to us as
oils.

Oleic acid, because it contains one double bond, is also referred to as
mono-unsaturated. Fatty acids that have multiple double bonds, like linoleic
acid in the first figure, are called polyunsaturated. Polyunsaturated fats
are also liquid at room temperature.

If you have a bottle of corn oil, what you have is a bottle of
polyunsaturated oil with a high concentration of linoleic acid. Because it
is polyunsaturated, it is liquid at room temperature. If you would like to
solidify it and turn it into margarine, what you do is hydrogenate it. That
is, you saturate it with hydrogen by breaking the carbon double bonds and
attaching hydrogen. To do this, you heat the oil and add pressurized
hydrogen gas and a nickel catalyst. In this way, you create "partially
hydrogenated vegetable oil." PHVO is the main ingredient in things like
vegetable shortening and margarine.

 

Fat and Health

Most of the nutrition science you hear about right now points to
mono-unsaturated fats as the good fats. Olive oil and canola oil are both
mono-unsaturated. Mono-unsaturated fats are thought to lower cholesterol.
In general, the fats to steer clear of are the saturated fats. Saturated
fats are bad because they clog your arteries. Partially hydrogenated
vegetable oils (which are artificially saturated fats) are now considered
totally evil, both because of the saturation and a side-effect of
hydrogenation called trans fatty acids.

Fatty acids that have double bonds come in two forms: trans and cis. "Trans"
and "cis" refer to the direction of folding that occurs at the carbon double
bonds in unsaturated fatty acids. Cis fatty acids are the normal, natural
directions for the folds. A trans fatty acid is chemically identical to the
cis form, but folds in an unnatural direction. The trans fatty acids are
created by heat (as in deep frying) and by hydrogenation.

It turns out that in the body, the enzymes that deal with fat are unable to
deal with the trans fatty acids (see How Cells Work for details on enzymes).
Therefore, the enzymes get tied up trying to work on the trans fatty acids,
and this can lead to problems with the processing of essential fatty acids

 

 

Essential Fatty Acids

The most common fatty acids are found in animal fats and include:
Palmitic acid
Stearic acid
Oleic acid
Your body is able to create these fats whenever it has a caloric surplus. It
can create them from straight sugar if there are enough sugar calories
coming in (see How Food Works for a discussion of carbohydrates and sugar).
It turns out that there is another class of fatty acids called essential
fatty acids that your body cannot manufacture. These fatty acids include:

Linoleic acid (LA) (omega-6)
Arachidonic acid (AA) (omega-6)
Gamma linolenic acid (GLA) (omega-6)
Dihomogamma linolenic acid (DGLA) (omega-6)
Alpha linolenic acid (LNA) (omega-3)
Eicosapentaenoic acid (EPA) (omega-3)
Docosahexaenoic acid (DHA) (omega-3)
Because your body cannot manufacture them, they must come in from the food
you eat.
Essential fatty acids fall into two groups: omega-3 and omega-6. The 3 and 6
refer to the first carbon double bond position on the fatty acid chain. All
essential fatty acids are polyunsaturated, so the 3 and the 6 mean that the
first double bond is either 3 or 6 carbons in from the end.

Omega-6 fatty acids are everywhere: corn oil, sunflower oil and soybean oil
all contain them. Omega-3 fatty acids are harder to find. Things like flax
seeds, pumpkin seeds and walnuts are high in omega-3 fatty acids, as are
salmon, trout and tuna. Current thinking is that these two fats need to be
balanced in the diet at a ratio like 1-to-1 or 2-to-1, rather than the
normal 20-to-1 ratio seen in most Western diets. About the only way to do
that is to supplement your diet with omega-3 vegetable oils or to start
eating fish in a big way (meaning two or three times a week).

 

So What Should I Eat?
Summarizing all of this information, the current scientific thinking on fat
consumption goes something like this:
Limit your fat intake to about 30 percent of the total calories you consume.
Do not try to cut fat intake altogether, because you do need the essential
fatty acids. A gram of fat has nine calories, meaning that if you consume
2,000 calories in a day your total fat intake should hover around (2000 * 30
percent / 9 calories/gram) 67 grams of fat.
When consuming fat, try to focus on mono-unsaturated fats like olive oil and
canola oil, or on essential fatty acids.
When consuming essential fatty acids, try to balance your intake of omega-6
and omega-3 fatty acids. Do that by consuming tuna/salmon/trout or omega-3
oils like flax seed oil.