By: Denis Faye
The short answer:
No way! Fat is a vital
nutrient! Just because it's called "fat" doesn't mean it makes you
fat. (On the same note, "fat-free" doesn't mean itwon't make
you fat. In fact, most packaged goods labeled "fat-free" make up for
it with added sugar, which can make you just as fat, if not fatter, than fat
can.)
But I digress. At its core,
I think this anti-lipid misconception stems from the fact that fat is easy to
overeat. It contains nine calories per gram, whereas carbs and protein only
contain four grams. Here's how that plays out in real life. Let's say your
afternoon snack calls for two tablespoons of peanut butter. If you do it right
and use two flush tablespoons, that's 190 calories. But if you get even a
little generous with your scoops—and we all tend to be generous when it comes
to nutty goodness—two heaping tablespoons will weigh in at something closer to
380 calories. I'd call that a diet-breaker.
So you want to moderate
dietary fat intake, but you don't want to eliminate it. It's an essential fuel
source you need for almost every human activity, including brain function. It
adds structure to cell membranes; acts as a hormone regulator; transports fat-soluble
nutrients such as vitamins A, D, and K; promotes the feeling of fullness; and
slows the absorption of carbs. Basically, it does everything short of wash your
dishes and walk your dog, so you absolutely, positively should not avoid it.
Your best bet is to get 20%
to 35% of your calories from fat. So, for example, if you're eating 1,800
calories, that's somewhere between 40 and 70 grams of fat.
Great sources of fat: Avocado; olives and extra-virgin olive oil; raw, unsalted
nuts and seeds and nut and seed butters, cold water fish.
The long
answer:
Low-fat proponents may
point out that your body can convert protein and carbs into fat. In other
words, if you're not eating enough fat, your body can usually convert other
macronutrients to suit its needs. While this is true, it's naïve to think we
should dodge a nutrient humans have thrived on since before we were humans.
There are four kinds of
fats, or "fatty acids": monounsaturated, polyunsaturated (PUFAs),
saturated, and trans. They're grouped this way based on how many carbon
atoms in the fat's chain are "saturated" with hydrogen atoms.
Monounsaturated fat has one loose (unsaturated) atom, while polyunsaturated
fats have several.
In terms of what you should avoid,
stay away from man-made trans fat. Small amounts of trans fat exist naturally
in dairy and sheep's milk products. The health benefits of these particular
fats are controversial, but I don't think it's worth stressing over. However,
the man-made stuff, created by partially hydrogenating a fat in order to
solidify it, is problematic. In fact, it's a major factor in heart disease.
Before it came under public scrutiny a few years back, it was fairly ubiquitous
in packaged baked goods and margarine because it increased shelf life. But, in
2006, the FDA made trans fat labeling mandatory, so it's pretty easy to ferret
out.
On the other end of the
spectrum, there's monounsaturated fat—the golden child of the lipid family.
It's been shown to improve cholesterol levels, ward off heart disease, and
improve insulin levels. You'll find it in plenty of foods. Avocados, sunflower
seeds, macadamia nuts, and olives are particularly high in monounsaturated fat.
Next come polyunsaturated
fats. Things get slightly more contentious here. On one hand, omega-6 and
omega-3 fatty acids—the only two fats essential to your diet because your body
is not capable of manufacturing them—are polyunsaturated. These two essential
fatty acids play a number of roles in the body, including formulating cell
membranes and being precursors to hormone-like compounds called eicosanoids.
Omega-6 eicosanoids tend to
promote inflammation, which is important in moderation because
inflammation is crucial to the healing process. On the other hand, omega-3
eicosanoids are anti-inflammatory, so they balance out the omega-6s. The
problem is, the American diet is packed with omega-6s, which you'll get from
many vegetable and seed oils, including safflower, grapeseed, and corn. But we
don't get a lot of omega-3s, which you'll find in flaxseed, walnuts, and
seafood—particularly cold-water fish like salmon, sardines, and halibut.
The downside of
polyunsaturated fats (in addition to the whole inflammatory imbalance thing) is
that they aren't very stable. When they go off (through a chemical reaction
called oxidation, which is the same thing metal does when it rusts) they lose
their nutritional benefits—some experts even believe they become cancerous.
So the trick with
polyunsaturated fats is to avoid consuming them in overly processed or heated
forms and get as many omega-3s as possible, especially fish, which contains the
omega-3 fatty acids DHA (docosahexaenoic acid) and EPA (eicosapentaenoic
acid)—both better utilized by the body than ALA (alpha-lipoic acid), the
omega-3 fatty acids that you'll find in vegetable and seed sources.
Finally, there's saturated
fat. Some nutritional schools of thought question saturated fat's negative
impact on cholesterol. However, there are still very current studies linking it
to cancer and type 2 diabetes, making the benefits of this fat a bit of a gray
area. That said, lumping all saturated fats together as "bad" may be
shortsighted, since an increasing body of research shows that various saturated
fats, which are differentiated by the length of their chemical chains, may have
different effects on the body. For example, lauric acid (which you'll find in
coconut fat) is a medium-chain saturated fatty acid that has been shown to have
a few beneficial properties, including functioning better than most fats as a
fuel source and raising HDL ("good") cholesterol, potentially making
it a "heart healthy" fatty acid.
(Lauric acid's potential
ability to increase energy expenditure, thus giving you a little extra boost
for your workouts in a calorie deficit situation, is why coconut oil plays an
important role in the 21 Day Fix™.)1
The notion that there are
many colors in the saturated fat rainbow is backed by a review by the Harvard
School of Public Health in theJournal of the American College of Nutrition entitled
"Types of Dietary Fat and Risk of Coronary Heart Disease: A Critical
Review." The review extensively points out the varying effects of the
various saturated fats, arriving at the conclusion that "the association
between saturated fat and coronary heart disease…was much weaker than that
predicted by international comparisons."2
But even though the sat fat
landscape is changing, nothing is concrete, so I don't see the point in going
coconut crazy. There's no denying that unsaturated fat also has a host of
benefits, so you might as well make those the cornerstone of your fat intake
and limit saturated fat to around 30% of your total fat intake. And make sure
to focus on the quality of your saturated fat sources, particularly organic, free-range
animal products, which tend to have a higher concentration of omega-3 fatty
acids, especially dairy.
In the past, it's been too
easy for diet gurus to point to fat as the evil in any diet. As you can see,
our relationship with dietary fat is much more nuanced than that. That may make
things a little more complex, but the upshot of weaving good fat into your
nutrition plan is that you get to eat things like nuts, olives, and wild
Alaskan salmon with impunity—and that makes it worth it, no?
Sources:
1.
St-Onge, Marie-Pierre, and
Peter J H Jones. "Physiological effects of medium-chain triglycerides:
potential agents in the prevention of obesity." The Journal of Nutrition 132.3 (2002):
329-332.
2.
Hu, F., Manson, J., &
Willett, W. (2001). Types of Dietary Fat and Risk of Coronary Heart Disease: A
Critical Review. Journal of the American College of Nutrition,
20:1 5-19.
No comments:
Post a Comment