Carbs may be the most demonized macro, but fats are somehow even more controversial. In certain circles (see: many whole-food plant-based diet advocates), they’re the hated macro and are kept to the very bare minimum in the diet. In other circles (see: the keto diet world), they’re the most important and most consumed macro in the diet, by far. Sometimes we hear there are “good fats” and “bad fats,” but we’re not always clear on what that actually means. Some maintain that eating dietary cholesterol (a type of fat) leads to increased cholesterol in the body and can lead to disease. Some encourage eating a dozen eggs every day.
So what gives? Who’s right? As always, it depends.
What is dietary fat?
Fats (or lipids) are the third major macronutrient in the diet. Like carbohydrates, they are made up of carbon, hydrogen, and oxygen molecules. They clock in at 9 calories per gram (vs. 4 calories per gram for carbohydrates and proteins), making them the most calorically dense of the macros. Dietary fat intake is ESSENTIAL for humans – we need to consume certain types of it in our diet to remain healthy and perform at our best.
Fats are needed to store and process the fat-soluble vitamins A, D, E, and K. They’re also needed to produce steroid hormones (like testosterone and estrogen). Plus, they’re delicious and a huge source of energy for the body.
There are four major types of fats found in the diet (these are the types you’ll see on many nutrition labels and when logging your food in calorie-tracking apps):
- Saturated Fatty Acids
- largely found in animal products and tropical oils (like coconut)
- solid at room temperature (think about what happens if you save your bacon grease – it hardens up for easy use in later cooking).
- Monounsaturated Fatty Acids
- Largely found in plant products
- Liquid at room temperature (think canola oil)
- Polyunsaturated Fatty Acids
- Again, largely found in plant products
- Include the Omega-3 and Omega-6 fatty acid families that are ESSENTIAL in the diet
- Liquid at room temperature, but start to turn solid when chilled
- Trans Fats
- While they do sometimes occur naturally in some animal products (milk and beef products), most are a product of the partial hydrogenation process in food manufacturing
- Manufactured Trans Fats are universally considered to be unsafe for consumption and are being phased out of processed foods in the US
- The only true definite in this post: manufactured Trans Fats are bad for you. Full stop. I won’t even elaborate on this. Don’t eat them.
We’ll get into some more detail on each of these in a minute.
A Brief History of How we Think About Fat
It wasn’t long ago that the official recommendation was to keep dietary fat as low as possible – the idea being that “fat makes you fat,” and low-calorie/low-fat diets were best to maintain a low bodyweight. Fat, after all, is the most calorie-dense of the macros, like we said above.
In the 1940s and 1950s, a series of studies showed correlation between diets high in saturated fats and cholesterol and cardiovascular disease. In response, the American Heart Association began promoting low-fat diets to those at risk for heart disease as a preventative measure – most notably the “Mediterranean diet” popularized by Ancel Keys and his Seven Countries study.
But notice – this was a diet change aimed specifically for those with or at risk for heart disease. Not for the general population. That all changed in the late 80s, when the federal government started publishing the US Dietary Guidelines. It was then that the idea of low-fat diets became mainstream. To capitalize on that change, food manufacturers started adding low-fat versions of their products – so in addition to skim milk products (now recommended for everyone over whole milk), there was a steady increase in the number of low-fat processed foods on the shelf, like cookies, crackers, ice cream (somehow), etc.
At the same time, obesity and metabolic disease in America was steadily climbing.
Something wasn’t working. Many of the major diets of the day followed the low-fat approach for weight loss and overall health, assuming that low-fat would also equal low-calorie. This was a false premise. When manufacturers removed the fat from their foods, they had to replace it with something to make the food taste good. That was typically sugar.
At the same time, the science was showing the limitations of low-fat diets. The super low-fat Ornish Diet, proven to lower cholesterol in heart disease patients, still only brought cholesterol down 5-10%. In addition, more was being learned about the Essential Fatty Acids, making it clear that not all fats are created equal. Nutrition is a young science – we’re learning more every year, and there isn’t always consensus among nutrition scientists.
And now we can see how the swing towards high-fat, low-carb diets came to be. If low-fat, high-carb didn’t work, than the opposite must be “the way.” The Atkins diet resurfaced and gained huge popularity in the 1990s, and when that fell out of vogue, other high-fat, low-carb options surfaced throughout the 2000s and 2010s, like Keto and Paleo.
Applying it all to Real Life
The general takeaway from the above history lesson – all diets are individualized, and moderation is probably the key for most of us.
We’ve learned a lot about fats in recent years:
We now know that the Omega-3 and Omega-6 Fatty Acids are ESSENTIAL for health, and must be consumed in the diet (your body can’t make them on its own!). It’s encouraged to pay particular attention to the Omega-3 fats. You’ve probably seen fish and krill oil on supplement shelves that proclaim that they’re a great source of Omega-3 fats called DHA and EPA. These two are a real powerhouse for the body – they have been shown to disperse LDL cholesterol in the bloodstream (that’s the cholesterol you don’t want) while raising the amount of HDL (the good type cholesterol). They’re also anti-inflammatory, which is a great bonus for athletes that put their bodies through a lot of inflammatory stress.
We also know that the old take on dietary cholesterol is overblown for most people. Those original studies demonized dietary cholesterol, assuming that consuming it would automatically lead to higher cholesterol levels in the blood, which is correlated with high risk of heart disease. First, cholesterol is not automatically bad. You NEED it – to produce enough steroid hormones; to synthesize Vitamin D; as a component of literally ALL of your cells. Second, in most people (some people are genetically predisposed to be hypersensitive to dietary cholesterol) eating cholesterol does NOT mean your blood cholesterol will increase. The more you eat, the less your body produces. The less you eat, the more your body produces. It’s a tightly regulated system. So eat some eggs (but probably not a dozen a day).
Those are just two examples. Again, the science on lipids is always evolving. We can only base recommendations on what we already know.
My take on all things eating is always to prioritize the nutrients that are health promoting and be reasonable about everything else. So in the case of fats, that means trying to get lots of mono- and polyunsaturated fats, especially for those Omega 3s.
That means aiming to eat a lot of wild-caught fatty fish (hello, salmon and sardines) that are a great source of EPA and DHA. It also means prioritizing fats like olive oil, avocado, and nuts like walnuts and almonds. So put some homemade olive oil and balsamic vinegar dressing on that salad – it’ll help you absorb some of the vitamins in your greens and veggies. Top it with seeds and walnuts. Enjoy it.
(Yes, there’s a lot of research out there saying that vegetable oils are the devil. They typically are very high in certain Omega-6 fats, and an unbalanced intake of Omega-6 vs. Omega-3 can cause inflammation. I typically avoid them for the most part, for no other reason than there are SO many other options that are more filling than just oils.)
When it comes to saturated fats, I don’t prioritize them, but certainly don’t cut them all the way out. I encourage leaner cuts of meat most of the time, and fattier cuts high in saturated fats occasionally. We’re all just living, and if a life without corn-finished fatty ribeye is not the life for you, that’s okay, just don’t forget to add some of those extra nutritious options too.
When it comes to overall amounts of fat in the diet, that’s highly personal. For myself and most athletically-minded people I work with, I aim for an upper limit on fats at 30% of total caloric intake – not a low-fat diet by any stretch. It typically ends up being between 20% and 30% for most, depending on activity level and training that day. I look at 30% as an upper limit for a pretty simple reason – there needs to be plenty of room for proteins and carbs for athletes!
And again, I cannot emphasize enough that this is all highly individual. Some people do very well with higher fat intakes, and some do better with lower fats than this. I can use myself as an example here: for my 21st birthday, instead of legal shots with my friends, I had my gall bladder removed. I now have to be a little extra careful with my fat intake, or I’ll face the consequences. I worked with a Registered Dietitian to figure out what those limits would be, and have used that information to figure out my own dietary needs since then.
This was a quick overview, and I didn’t mention a TON of information that others delve deep into – Omega-3s in grass-fed vs. corn-fed beef, is coconut oil good or bad, is MCT oil the holy grail energy source for endurance athletes, etc. I encourage you to seek that out if you want to get down in the nitty-gritty of what’s going on with nutrition.
Finally, the TL;DR:
Fat is ESSENTIAL in the diet, and we need to prioritize eating foods high in Omega 3 and Omega 6 fatty acids. A diet that consists of up to 30% of calories from fat is probably a well-balanced one that leaves plenty of room for the other macronutrients. Eggs will not kill you. Avocados are awesome. Trans Fats are out. Don’t be afraid of fat. The end.