We were all indoctrinated early. Living anywhere in the civilized world (but especially in the grain-obsessed US) it was ingrained in us: Carbs are a dietary staple. Eat 6-11 servings of carbs per day. etc etc
There's now a lot of evidence showing that this long-running carb-dogma is actually quite misinformed.
Carb-restricted, high-fat diets are growing rapidly in popularity and deliver excellent results for a ton of people. The best high-fat diets of today are a world better informed and more sophisticated than early carb-restricted diets of the mid-to-late 90's (Atkins, etc).
In fact, I believe that a switch to a high-fat diet can potentially be one of the most transformative nutritional practices a person can adopt. Speaking personally, the switch to a dialed high-fat diet has completely revolutionized the performance of my own body and mind.
Here's some things to consider:
1. Evolutionary Evidence
There are a few pretty convincing points that show the majority of our evolutionary history was spent eating a high-fat diet.
- Anthropological Evidence - When anthropologists look at the diets of pre-agricultural societies, the vast majority of them got the bulk of their calories (somewhere around 60%) from fats. As hunter-gatherers, most of these fats were animal fats. This is significant, as animal fat is primarily comprised of short-chain fatty acids that the body uses very efficiently (we'll touch on this later).
- Diets Of Other Mammals - The diets of mammals vary widely, of course, but there are a few patterns to note. Carnivorous animals eat a very high percentage of their calories as fat, sometimes up to 80%.
On the other end of the spectrum are grazing animals (such as cows, horses). While at first glance it seems that they eat almost entirely carbohydrate, there is a critical difference in the way these animals process their food. Bacteria in the digestive system of a grazing animal converts fiber in the food into other types of nutrients, particularly short-chain fats. So although grazers eat primarily carbohydrate, by the time food is digested, it is primarily these short chain fats that are delivered to the brain and body. A cow, for example, eats almost entirely grass but gets close to zero carbohydrates in it's diet (as but bacteria transform the grass into short-chain fats).
Omnivorous mammals (like pre-agricultural humans) tend to eat around 60% of their calories from fat when food scarcity is not a factor and they can make choices based on preference.
So what can we learn here? First - in human history, diets with a large portion of the calories coming from carbohydrates is an entirely post-agricultural-revolution phenomenon. This means less than 10k years ago. Prior to that, diets were almost exclusively low-carbohydrate and high in animal fats.
Hominids first started to appear 22 million years ago and modern homo sapiens around 200k years ago, so that gives you a sense of what a small percentage of our evolutionary history has been spent eating high-carbohydrate diets. The evidence from the diets of other mammals only drives this point home.
While the evolutionary evidence is intriguing, it's admittedly meaningless without some more practical, applied evidence of the benefits of a high-fat diet. Fortunately, there is no shortage of this either...
2. Escape The Blood-Sugar Cycles
To understand why fueling the body with fats is so beneficial, it's useful to first consider what takes place in our bodies when we eat a carbohydrate-heavy meal. After you eat a carb-rich meal, over the next 30 minutes to 3 hours-or-so, your digestive system will break down the carbohydrates in your meal and convert them into simple sugars so they can be absorbed into the bloodstream. (how quickly or slowly this happens depends on the types of carbs and how much fiber, fat and protein were in the meal)
Correspondingly, blood sugar rises and metabolism (and thus, available energy) rises along with it. Insulin is released and tells your cells to start storing all of this carbohydrate (as glycogen or fat).
At some point, blood sugar peaks and then starts to fall. Shortly thereafter your brain notices that it no longer has enough blood sugar to fully function. Your cognitive performance dips, energy levels drop, you get moody and your brain triggers your hunger mechanism.
You eat again and restart the cycle: Eat. Blood sugar up. Blood sugar down. Repeat.
Your body has other potential energy sources it could mobilize - stored glycogen or fat - but it won't because by eating a diet heavy in carbohydrate, you've trained your body to use primarily carbohydrate from the food you consume for energy. Your blood sugar has to drop significantly for an extended period before your body will start to mobilize stored energy sources in adequate levels. In essence, you're trapped. If you don't continue eating carbohydrate regularly throughout your day, you're going to feel like shit.
If all of this blood sugar up, blood sugar down sounds like it would be taxing for the body, you're right - it is. Overall energy levels and cognitive performance end up being lower than if your brain and body had been fueled more stably throughout the day.
This is where a high-fat diet has the potential to be hugely beneficial...
3. Improved Energy Levels
Now that we have a picture of how a carbohydrate-dominanated diet affects the body, let's contrast this with how the body uses fats.
Fats and carbohydrates are both digested in the gut, although fats break down quite a bit slower. After digestion in the gut, most carbohydrates are absorbed directly into the bloodstream (as glucose, a simple sugar). Fats, however, go to the liver for an additional processing step, either for storage or conversion into ketones. It is these ketones that your brain and body are able to use for energy metabolism in place of sugars.
Where carbohydrate digestion is defined by a dramatic rise-fall of available metabolic energy as blood sugar peaks then falls, fats are converted into energy stably and consistently over many hours.
When your body is procuring the majority of its energy from fats, your metabolism is in a state referred to as ketosis. Everyone with a healthy metabolism will switch into ketosis at least once in a 24-hour period (generally during sleep). The fundamental idea behind a high-fat diet is to eat the foods that keep your body in ketosis for the majority of a 24-hour period.
Why? For one, the way you experience your energy levels while in ketosis compared to in carbohydrate-metabolism cycles changes dramatically. Gone are the dramatic swings in energy levels; the late-morning lulls, mid-afternoon drowsiness, etc. Gone too are the swings in mood that often accompany these swings in energy levels. For a lot of people, even their experience of hunger changes and lessens.
When your body is trained to operate efficiently in ketosis (nutritionists refer to this as keto-adapted), you experience energy as stable, consistent and abundant.
4. Better Cognitive Performance
No organ in your body thrives on ketones more than your brain. One of the most common benefits reported by people who switch over to a high-fat diet is improved mental clarity and cognitive performance. There's a few reasons why this is the case...
First, is a simple energy consideration. The brain accounts for around 2% of our body weight, on average, but can use as much as 25% of the body's energy in a given day. Because of this high rate of energy usage, the brain is stressed by cycles of high- and low-blood-sugar more than other tissues in the body.
The second reason the brain prefers ketones as a fuel is more specifically a neurochemical one. Glutamate is an amino acid that functions in the brain as an excitatory neurotransmitter. The brain will also convert glutamate into one of two things, GABA (an inhibitory neurotransmitter) or aspartate (another excitatory neurotransmitter). Maintaining a balance between GABA and these excitatory neurotransmitters is crucial to optimal brain functioning.
For reasons we're not quite sure of, a brain using ketones for energy preferentially converts glutamate into GABA, maintaining a healthy balance. A brain using glucose (carbs) for energy converts glutamate primarily into aspartate, resulting in an excess of excitatory neurotransmitters, a state that is mildly neurotoxic for the brain (or significantly neurotoxic depending on the degree of imbalance).
Finally, the metabolic processes that convert ketones into energy are a bit "cleaner" than those that convert glucose into energy. Glucose metabolism produces slighly more oxidative free-radical byproducts than ketone metabolism. In the rest of your body where toxins are cleared readily, this isn't a big deal. Your brain, however, a highly sensitive organ where energy usage is quite high making this a bigger concern. Higher levels of oxidative byproducts means more damage to sensitive neuronal membranes and negatively affected mental performance.
It's an interesting side note that recent studies have shown coconut oil to be a surprisingly effective treatment for alzheimer's and other neurodegenerative diseases. Coconut oil is a rich source of MCT's, a specific type of fat that converts readily to ketones and promotes ketosis in the body.
5. Improved Body Composition - This is somewhat counterintuitive at first glance - the idea that eating large amounts of fat could actually lower your overall body fat. But, indeed, this tends to be the case more often than not.
This is in part because the metabolic pathways that convert fats from your diet into energy are largely the same pathways that turn stored body fat into energy. When your body becomes keto-adapted, these metabolic pathways become more robust and your body "gets better" at burning its own fat stores.
Implementing A High-Fat Diet: Things To Consider
There's a lot to consider when embarking on a high-fat diet. Really, this deserves a whole article in itself, but for now, here are some pointers.
- Allowing The Body To Adapt - I've used the phrase "keto-adapted" a few times throughout this article, an important idea to consider when starting a high-fat diet. The metabolism of someone who is months or years into a high-fat diet looks quite different than that of someone eating a standard carb-dominated diet. Over the first few weeks of a high-fat diet, your body will up-regulate production of the enzymes involved in the digestion and conversion of fats into ketones.
- The Types Of Fats Matter - Certain types of fats are converted far more readily into ketones by your body. Specifically, short- and medium-chain saturated fats require minimal digestion in the gut before they can be sent to the liver for conversion. Because they are converted into energy so easily, these fats actually encourage your body to move into ketosis quicker and stay there longer.
Good sources of short-chain fats include butter and ghee (although anything not completely grass-fed/pasture raised should be avoided).
Medium-chain fats are found in a number of plant oils, but far and away the cleanest source for these is coconut. Coconut oil is about 65% medium-chain fats by volume. I am a huge fan of Cocotella, an artisan raw coconut butter. It is an excellent source of medium-chain fats plus a good source of soluble fiber to keep the gut flora happy. (Oh, it's completely delicious)