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Fat is a very confusing topic for a lot of people and for really good reason. In the 80s and 90s, we were inundated with messaging that fat is bad for you and the source of the American obesity epidemic and chronic illnesses. However, in recent years, it’s come to light that fat isn’t the evil we once were told it was and that sugar is actually a bigger problem (in spite of the sugar industry’s relentless lobbying efforts). But, it seems that some have taken advantage of this change in the tides and have taken the fat message in the opposite direction, creating diets that claim that eating lots of fat is healthy and will help you lose weight. And then there are the different kinds of fat with vague names that make it hard to keep them straight – saturated, unsaturated, trans, omega-3s, polyunsaturated, omega-6s…it’s dizzying. In this post, I’m hoping to clear things up for you.
Before we can talk about good fats vs. bad fats, we should cover what their names mean.
The dietary units we call “fats” are actually fatty acids which are made up, in part, by a chain of carbon atoms. When every carbon atom in the chain is bonded to a hydrogen atom, it is called a saturated fat. I remember this by thinking of the hydrogen as saturating the fat like water saturates a sponge so that every bit of the sponge is soaked.
Saturated fats are generally solid at room temperature – so foods like butter, coconut oil, cocoa butter – these are saturated fats.
Saturated fats are often thought of as unhealthy fats, but that is not necessarily the case. Here is where it gets a little complicated: within the saturated fats category, there are short, medium, and long chain saturated fats. There is an important role in our diets for short and medium chain saturated fats: they help stabilize our cell membranes, help us convert Omega-3 fatty acids into usable forms, have antimicrobial properties, and have anti-inflammatory properties. Coconut oil falls into the medium chain category and that is the root of what makes it a healthy fat option. The health concerns come from overconsumption of the long chain saturated fats, such as animal fats, dairy fats, and cocoa butter. These are the fats whose excess consumption is linked to high cholesterol levels and heart disease. They also are higher in calories and are stored in our adipose, or fat, tissue. Unsurprisingly, Americans in general eat too much of the long chain saturated fats and not enough of the short and medium chain ones.
So what does this mean the fat in your diet should look like? This means eating lean cuts of meat (beef, pork, poultry, etc.), low-fat dairy products, and minimizing our consumption of things like butter. When it comes to the short and medium chain saturated fats, they do play an important role in our diet, but we don’t need to be eating a lot of them to derive the benefits and it’s important to remember that fat is a calorie-dense food. Therefore, moderation really is the key.
Since we now know that saturated fats have all of their carbon atoms paired with hydrogen atoms, we can guess that unsaturated fats have one or more carbon atoms not paired with a hydrogen atom. Instead, those unpaired carbon atoms form double bonds with the carbon atoms next to them. This chemical structure makes unsaturated fats less stable than saturated fats so they are liquid at room temperature. Examples of unsaturated fats are olive oil, flax seed oil, and fish oil. These are fats that are more vulnerable to going rancid and becoming carcinogenic when cooked to temperatures too high.
Unsaturated fats play very, very important roles in our diet, including: brain development and energy, maintaining healthy body tissues and skin, regulating our hormones, assisting in the absorption of fat-soluble vitamins, and cushioning our organs. These are very healthy fats that we should consume regularly.
Within the unsaturated fat category, there are two types: monounsaturated fats have one double bond between carbon atoms while polyunsaturated fats have multiple double bonds between carbon atoms.
Omega-3 Fatty Acids
Omega-3s fall into the polyunsaturated fats category and are often considered the healthiest fat. Omega-3s are found in fatty fish, like wild salmon, flax seeds, and Omega-3 eggs. While Omega-3s are found in plant sources such as flax seeds, it’s important to note that the form those fats take in plants are not a form that the human body can readily use (ALA). This means that our bodies must first convert them into usable forms (EPA & DHA) before they can be used. Unfortunately, after that conversion occurs, our bodies’ absorption rate of those fats is less than 5%, so it’s more efficient to consume Omega-3s from fish sources than plant sources.
The health benefits of consuming Omega-3s include: building healthy brain cells, helping to reduce the risk of heart disease, lowering the rate of certain cancers, elevating our mood, and improving our learning, attention, and vision. In general, we Americans do not eat enough Omega-3s.
Omega-6 Fatty Acids
Omega-6 fatty acids are also a form of polyunsaturated fat that are very good for us. They play a critical role in our brain function and normal growth and development, among other roles. They are found in vegetable oils, pumpkin seeds, walnuts, edamame, and sunflower seeds. In general, Americans consume plenty of Omega-6s. The ideal ratio of Omega 6 to Omega 3s in our diet is 2:1.
Trans fats are the bad fats. These are fats that do not occur naturally; rather, they are created by taking an unsaturated fat and adding hydrogen molecules to it, a process called hydrogenation. This was a profit move by the food industry in the early 1900s to stabilize vegetable oils so they would have a longer shelf life (the invention of Crisco). Trans fats have become very common place in prepackaged foods these days although there is a perception that they have fallen out of favor since the backlash against them. However, this is the food industry being sneaky. Legally, if a food contains less than 1/2 gram of trans fat per serving, they can put “0 grams trans fat” or “trans fat free” on a food package label. The lesson here: you can’t trust what the front of a package says. Instead, what you need to do to determine whether a food contains trans fats is to look in the ingredients list for the word “hydrogenated.” Hydrogenated oils are trans fats.
There are a number of compelling reasons to avoid trans fats: their consumption has been linked with low birth weights, high blood sugar, increased LDL (“bad” cholesterol), a decrease in nutrition density levels, a decrease in visual acuity, a decrease in Omega-3 levels in the brain (which we now know play a critical role in brain function), and a decrease in HDL (“good” cholesterol).
What About the Keto Diet?
The recent rage in fad diets has been putting your body into a state of ketosis by decreasing our carbohydrate consumption to very low levels and increasing our fat consumption to force our body to burn fat for energy. There are a number of problems with this diet craze.
For one, our bodies don’t burn fat for energy anywhere near as efficiently as they burn carbohydrates for energy. So by cutting our bodies primary fuel source drastically, we are depriving ourselves of the energy we need. Many on keto diets will experience low energy levels and mood levels because of this.
Secondly, you can overdo it with fat. The saying “too much of a good thing” really applies here. Yes, fat plays an important role in our diets but eating too much saturated fats (long chain), for example, can increase your cholesterol levels and increase your risk of heart disease. Furthermore, on high-fat diets such as this, you can’t be just indiscriminately eating loads of fats. The healthiest way to to eat is to focus on fish and plant sources of food. You want the majority of the fats you eat to be unsaturated, particularly polyunsaturated. Cutting carbs and eating loads of meat and butter and dairy may help you lose weight for a little while but it can have negative long-term health effects.
Finally, and perhaps more practically, this diet is not sustainable. Keto dieters may lose weight for a period, but they will crave carbohydrates and will swing back in the other direction and gain that weight back. This is simply what happens with deprivation in humans. This can contribute to a pattern of yo-yo dieting which has been shown to contribute to a slower metabolism over time and higher weights.
When it comes to fats, high fat or low fat isn’t answer. Right fat is the answer. If your focus is on eating healthy fats, omega-3s, omega-6s, and other unsaturated fats like olive oil with a balanced diet, then you are eating a right fat diet, supplying your body with the fats you need without negative health impacts.