Ask the Expert: Should You Avoid Fat?Jan 8, 2019
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 it won’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 absolively, postitutely 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. Dodging fat adds unnecessary tasks to your already overtaxed system (thanks to the modern-world stress and toxins we all have to contend with) and denies you a few fatty acids that your body cannot, in fact, produce.
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.)
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 the Journal 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.”
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?