Throughout the latter half of the 20th century, dietary fat was painted to be a villain. But, when you start to dig into the history of dietary fats and nutrition recommendations what you get sounds more like a juicy political thriller than science. Let’s dig into a little bit about the history of nutritional guidelines on fat and what dietary fats do for our bodies, and you can decide if it’s time for fat’s redemption arc.
When did fat become the bad guy?
Let’s hop in the TARDIS and go on back to the turn of the 20th century. In the 1900s, pneumonia was the leading cause of death in the US, and people – on average – lived to be about 50. But, thanks to science’s focus on infectious disease life-expectancy began to increase. And with longer lives came, well, the body’s tendency to break down over time.
By the 1910s, scientists had developed a better understanding of how to study the human heart and better diagnose heart attacks and heart disease. By mid-century, a clear pattern was emerging – a build-up of cholesterol in the arteries leading to blockages.
However, this phenomenon was not happening worldwide. In fact, countries, where diets were low in saturated fats, had lower rates of heart disease. This became standard dietary advice for the latter half of the 20th century.
But, other studies around that time pointed the finger at another cause of coronary heart disease: sugar. Why did these ideas fail to get the same sort of scrutiny?
Well, you know how Big Tobacco paid out big bucks to try to hide the dangers of their product even though they knew it was bad for the public? Well, Big Sugar took a page out of their playbooks.
A lot of low-carb and keto proponents point to this as proof that carbs are evil. I covered Carbohydrates, including sugar, in their own Macro Profile here.
Recently, this political wheeling and dealing has come to light. However, if you’ve ever read a pop-science magazine you’ll know “experts” seem to be changing their minds about what is good for you one day to the next.
Types of Dietary Fats
Polyunsaturated Fatty Acids (PUFA) & Monounsaturated Fatty Acids (MUFA)
These two fats are considered to be important parts of a healthy diet. If you were to take a microscope and get a look at these molecules, you’d see that they’re kind of bendy looking which results in forming a viscous liquid.
This is to say, at room temperature, PUFAs and MUFAs are oils. Yes, the olive oil or canola oil you cook with, but also the oils found in avocados, nuts and seeds, and fatty fish. Current research shows that a diet full of these unsaturated fats can lower levels of LDL Cholesterol – aka “the bad kind” which can clog the arteries.
Unlike unsaturated fats, at an atomic level, these fatty acids have a completely straight structure to them and are solid at room temperature. Typically, these kinds of fats are found in animal products — like meat and dairy — but are also found in some tropical oils like coconut and palm oil.
Saturated fats long bore the brunt of the coronary heart disease blame, but now research is mixed, to say the least. You can spend hours on PubMed looking through conflicting studies on saturated fats. Walk through any health food store, and you’ll see coconut oil lining the shelves even though it contains more saturated fat than butter.
The consensus seems to be to consume these fats in moderation, due to the fact it can raise LDL levels. But some studies also show it can raise HDL levels as well. HDL cholesterol seems to travel through the body, and can even “steal” some LDL cholesterol from arterial walls to help maintain blood circulation.
I’m just saying, you’ll be prying my full-fat greek yogurt out of my dead lactose-intolerant hands.
Trans fats (or the thing I did a science fair project on in 8th grade)
Awareness of trans-fats has been growing for a few decades and chances are you’ll see “no trans fats” used in marketing materials. Fun fact! In the US, you can market a product with less than 5g of something as having “none” of that thing.
Now, some trans fats are naturally occurring, and they have a structure somewhere in between saturated and unsaturated fats making them semi-soft at room temperature. Natural trans-fats make up about 2-9% of the fats in dairy products and certain cuts of meat from grass-eating animals. Think cattle, sheep, and goats. These levels are not considered to be harmful; in fact, conjugated linoleic acid, or CLA, is a trans fat that is often sold as a dietary supplement.
The real danger lies in industrial trans fats, also known as hydrogenated or partially-hydrogenated fats. This involves taking a vegetable oil, or unsaturated fat, and chemically altering it so that it is solid and shelf-stable at room temperature. Think margarine or shortening.
Studies have shown that industrial trans fats can lower HDL cholesterol, raise LDL cholesterol, which can increase the risk of heart disease.
If you’re picking up cookies, chips, cakes, frosting, crackers, popcorn, and other shelf-stable goodies from the center aisles of the grocery store, make sure to check the label for partially-hydrogenated oils to try to cut down on this type of fat.
Why You Need Dietary Fats
Like protein and carbs, the body needs to break down fat into its basic components – fatty acids – to be used. The body can create some of the fatty acids it needs to function, but not all of them — so for your body to function properly, you do need to consume these fats. These “essential” fatty acids are omega-3 and omega-6.
Fatty acids are a secondary energy source for the body. While the body will use available glucose before going after fatty acids, fatty acids provide more energy per gram than glucose. (A gram of fat contains 9 calories of energy, opposed to a gram of carbohydrates which provides 4 calories.)
Those essential fatty acids are also crucial for the health of our brains and our eyes.
Dietary Fat vs Body Fat
Contrary to what you may think, dietary fat does not automatically become body fat. Body fat stores leftover energy when we’ve eaten more than we need to support our activity level.
Unless you’re following a ketogenic diet, common dieting advice is to eat a “low-fat” diet. Now, as we saw earlier, gram for gram fat contains more calories than carbs or protein. However, studies show a caloric deficit is all that is needed to burn body fat. (Regardless of what the macronutrient composition is.)
If losing body fat is part of your current goals, dietary fat does not need to be feared.
Body Fat Is Still Important
I’ll say it again for those in the back: body fat is important! Body fat regulates body temperature and stores fat-soluble vitamins. It is also an active part of the endocrine system and plays an important role in regulating various hormones.
In fact, the body needs essential levels of body fat to function properly. There’s also a level of body fat where it’s effects are no longer beneficial. We’ll do a deeper dive into body composition and its importance in another article.
What does this mean for you?
Trying to drastically remove fat from your diet may not have the health benefits you would expect. Fats are a crucial part of the human diet! There may be some benefit to swapping out your butter for oil, but not for margarine. (I’m having flashbacks to my grandmother’s fridge right now!) Aim to get your fats from whole food sources like nuts and olives, and less from fried or overly-processed food.
If this article was helpful to you, don’t forget to share on social media!