The basics of fat and its role in our meals and lives
By Rachel Roth
There is much mystery surrounding
fat. Does eating fat make us fat? Why
are some fats considered good for
you? Should we be trying to eliminate
fat from out diet altogether?
The first, most important thing to
understand is that when doctors and
scientists use the word “fat” in a nutritional
context, it is different from
a lay person’s use of the word.
In science, fat is the term for a certain
chemical structure. Anything
with that general structure, though
they may vary in their details, is
called a fat, or “lipid.” An analogy
would be that we can all identify a
car on the road as a “car,” because
they are similarly structured,
though the cars may vary from each
other in their details. This will
become important soon. But to be
clear, I’ll use the term “lipid” for
this certain chemical structure.
The fat on our bodies that we
are forever trying to lose is actually
termed “adipose” in scientific
lingo. Adipose tissue is made up
of storage cells that hold on to any
food that we ate but did not burn
with exercise. These adipose cells
are relatively large, and packed full
of sugar and lipids. When we gain
weight, it is because we put more
sugar and lipids into our adipose
cells, making them fatter. When
we lose weight, it’s because we take
those things out of the adipose
cells, and they shrink (allowing us
to fit back into those old pants).
Now that we know that, we can understand
why we need lipids in our
diet. Many things our body requires
have a lipid, or fatty, structure:
hormones for example, estrogen and
testosterone, are made of lipids, and
are certain vitamins like vitamin D.
Additionally, they are important in
signalling our body to feel full and
satiated from a meal; one gets hungry
quickly again when there is no fat in
the meal. Lipids are necessary for life.
Where are these lipids found? In
any fatty food – from non-skim milk
to meat and fish to the oils we cook
with and the butter on our bread. So
rejoice that these fats in your food are
not evil. If we do not eat too much,
and our body uses all the lipids that
we eat to create these substances
(hormones, vitamins, etc), they are
never sent into storage in the adipose,
and do not contribute to making us
fat. Remember: weight is only gained
when something is eaten and not
burned up by the body, and in turn
put into storage in the adipose.
So why are doctors so down on fat?
Well, not all lipids are created equal.
This comes back to there being
slight differences between lipids, as
between cars. Some lipids are “cleanburning,”
meaning that they are
used completely by the body with no
leftovers. These are “good fats,” such
as the oft-praised omega-3’s, and are
found most abundantly in fish and
fish oil. Such lipids are strong chemical
protectors of the body against
heart disease, cancer, and many
other ills. Other fats that are good are
“unsaturated,” but these exist in oils
such as olive oil, and are much better
for the body.
Unfortunately most of our fat intake
comes from “bad fats” – saturated fats
like those in milk, meat, and sweets.
These are like cars which pollute;
the byproducts of breaking them
down leave behind junk in our blood
vessels, the build-up of which leads
to heart attacks, strokes, and poorer
The take-away is that lipids are
needed for life, and should not (nor
can you realistically) cut them out
of your diet completely. The trick
is not to pollute the body with
bad fats, but to choose good ones.
Substitute olive oil for canola oils,
chicken for beef, and skim or one
percent milk for whole milk. And
include lots of fish in your diet.
Fats are not the enemy – they just
need to be understood and used
smartly in moderation to optimize
Rachel Roth will be going into a
Family Practice residency in Seattle,
starting in July.