When I lived in downtown Charlotte, NC, there was this great breakfast and lunch restaurant located directly beneath my apartment. Now it’s a food truck, but that’s neither here nor there.
"No, we don't serve tacos. Why does everyone keep asking that?"
It was one of those deals where you write what kind of sandwich and toppings you want on a brown bag with a sharpie and hand it to the guy behind the counter.
They had quality ingredients, and the owner was a great dude, so I’d pop in there a few times a week and always fire up a couple of breakfast sandwiches (salmon/cream cheese/eggs and pulled pork were my standbys), in a bowl without the bread.
One particular morning, a fairly young and extremely skinny guy, probably enrolled in one of the nearby colleges, looked at my bread-less order and said something along the lines of, “Dude, you know carbs are the body’s main source of energy, right? Why would you get this without bread?”
About 25 potential responses ran laps around my brain, ranging from jovially comedic to aggressively berating. I settled on something neutral, possibly even empathetic, which is super hard for me, by saying “Yeah man, that’s what they taught me in college too. But your body only runs on carbs if that’s what you train it to do”.
Although he was completely out of line by basically telling me how I should eat, he wasn’t entirely incorrect. The human body does run off of carbs as its main energy source…when carbs are continuously supplied. Most people don’t realize that once you restrict this supply, and adequately replace it with fats, the body does an amazing job of using fats and ketones instead.
Why don’t more people get this, why isn’t this concept adequately addressed in undergrad nutrition education, why do people “feel like crap” when they cut carbs? The answers to these questions could all be long articles individually, and I want to keep this as a semi-brief primer for people new to the concept, so I will try to answer these questions and more while embracing brevity to the best of my ability. Once we get to parts II & III, I'll be including links to some other websites that have already done a beautiful job of describing fat-adaption and keto-adaption.
To kick off the search for clarity around this misunderstood topic, I’d like to present the concept of a three-state metabolic continuum, which, over the years, clients have really seemed to enjoy as I sketch on a piece of paper, likely due to its simplicity. That came out wrong. Not because they're dumb, because this can easily go down the rabbit-hole of nuanced madness, and this continuum illustration drives home the key points while being easy to remember.
Basically, your body runs pretty well on either carbohydrates or fat, or sometimes, in some people, in some conditions, a combination of both quite efficiently. Think of it as a gasoline vs. electric vs. a hybrid car.
Now, in reality, the body is pulling from different energy stores, just in varying percentages, most of the time. So if you’re at work sitting at your desk watching Arrested Development on Netflix as you should be, you might be fueling yourself with 70% fat and your co-worker in the cubicle next to you might be fueling at 70% carbs (glucose). There are times when you might be pulling from 100% of one or the other. This is purely for clarification; I don’t want to get tangled up in the intricacies of substrate oxidation here, because that’s beyond the point I’m addressing. The body even uses protein as a percentage of fuel…but, yeah, yawwwwn. On to the three metabolic states:
Carb-adapted
This is the most common metabolic state. Why? Well, most people alive today have been raised on “balanced meals” consisting mostly of starches and a bit of protein because that’s what we’ve been taught to eat.
We think fats and oils are dangerous and should only be consumed “in moderation”.
Bread (whole-grain, of fucking course), cereals, rice, pasta, low-fat dairy, granola, oatmeal, or whatever, are all deemed safe foods that lower cholesterol and contain only microscopic amounts of super scary saturated fat.
Because of this mindset, everywhere you go, whether it’s the grocery store or a restaurant or a vending machine or a school cafeteria or MRE’s in the Army, carbohydrates are in abundance.
Even physique athletes, at large, still tend to gravitate towards chicken and rice over rib-eyes and butter. They just tend to have more on the line over the general CPA or soccer mom since they've dedicated a portion (or all) of their lives to being ripped. And/or those with the proper psychology for calorie restriction and insane willpower are drawn towards the sport like Dominicans are to playing shortstop. And then there are the drugs...which, is not the whole story, but it's a chapter.
No matter who you are, it doesn’t take a lot of carbs to keep the body in a carb-adapted metabolic state. It is, by far, the easiest metabolic state to be in based on our societal norms.
It’s just the default for us. If I drop you on a lowly populated island with a rifle, a fishing pole, and a basket…you’re going to have to work pretty hard to gather enough of these to fill up that basket every day to keep yourself carb-adapted.
Internet nutrition gurus love to argue back and forth all day long about exactly how many grams of carbs the Inuit people or whatever other primal-esque societies have had access to throughout each day of history, blah blah blah, I don’t care, the point is that we live in a society of carbohydrate abundance, it’s just normal to eat grains with every, single, meal. And this, my friends, will keep you carb-adapted.
For those of you that love to think in binary terms, I know you’re thinking, “So is carb-adapted bad?”
The answer to almost every question which embraces the logical fallacy of providing only two answers when more are available, is, “it depends”.
Some people can go their entire lives being carb-adapted and enjoy pristine health, praise-worthy blood lipids, seamless digestion, excellent performance, clear and focused thought, consistent energy, and low body fat levels. Genetics plays a huge role in this. To keep it simple, here is the ideal person that can rock out with their baguette out, all day every day:
Young + insulin sensitive + active + expend more calories than they consume
That’s four things. If you have all four going for you, you’re pretty much golden. If you have three, you’re probably still good, for a while. If you have two, you’re on short time. If you have one…ehhhh good luck. Better off than somebody with zero.
But what happens when one or more of these four dynamic factors starts to change? The diet that was working for you previously is now disastrous. That whole "once you stop working out muscle turns to fat" adage? Your fat ass just needs to eat less now that resistance training isn't part of your routine anymore, there's no muscle turning to fat.
High carb habits are super fun when you're young and can get away with it, then one day you wake up and see 30 candles on your birthday cake, and it's time to re-efucking-valuate.
Been blasting your cells with insulin your whole life and suddenly oatmeal and orange juice every morning make you fat? Ever tried forcefully spinning a Phillips screwdriver counter-clockwise over and over into a slightly stripped screw? Yeah, it doesn't just magically get unscrewed. Neither do you.
In this carb-adapted metabolic state, your body is super good at using glucose for fuel, and super bad at liberating and/or oxidizing stored fat. This is why a carb-adapted person can spend an entire day sitting on the couch watching TV, all but motionless other than changing the channel when an LPGA event comes on, and still become ravenously hungry several different times, a couple of hours after eating calorie-dense meals. How is it that you can eat half a pizza, seven breadsticks, text a few people, watch an episode of Game of Thrones, scratch your balls, then be starving again? What the hell did your body just do with those 2,500 calories? Why is your brain telling you that more food needs to get in your pie-hole asap when you’ve barely moved?
Your body is running on glucose, which has a limited storage capacity, and it can’t tap into fat, which has a figuratively endless supply of fuel for you to use, if you could sort out how to get at it.
Here’s a slide from one of my webinars:
My analogy, which I think I borrowed from either Peter Attia, or Volek & Phinney, or maybe I made it up, I wish I could remember so I could give proper credit…was that of a fuel tanker driving across the country. The driver has to stop and refuel the tiny tank represented by the small blue arrow on the left, quite frequently, even though he has this huge fuel tank (represented by the large blue arrow on the right), which he can’t access.
This fuel tanker truck is your body. The little tank is the combination of your liver and muscle storage of carbs (glycogen, or the storage form of glucose/blood sugar). The big tank is your fat cells.
Even if you’re lean, the big tank is huuuuuge in comparison.
I used to test Resting Metabolic Rate (RMR) on hundreds of clients, and this all starts making sense when you realize that the average RMR for U.S. adults is 1,400 – 1,600 calories. So just for your body to carry out its normal cellular processes to keep you alive, you’re burning let’s say 1,500 calories, and the average carb fuel tank is 1,400 calories.
Granted, as previously mentioned, you aren’t pulling 100% of your calories from carbs lying on the couch, nor does your body hit 0% glycogen before you start getting major hunger signals. But why are you getting an intense signal to eat, at all, when you have 50,000 calories of fuel in your fat cells ready to party? Because you’re carb adapted, and your body sucks at tapping into those fat calories.
I’ve already gone on longer here than I wanted to, so I’ll sum this up with some bullet points:
Advantages of Carb-adaption
You get to eat carbs, frequently, and carbs are delicious. Hence why IIFYM is so fucking popular.
Performance is typically great (relevant variables accounted for, if you suck at basketball you won’t be better at basketball by eating more carbs)
Certain genotypes will likely be healthier and run a lower risk of heart disease with a higher carb/lower fat diet (ApoE 3/4 and ApoE 4/4). This can be easily tested, and should. ApoE 3/4 and 4/4 folks also suck at excreting toxins like mercury, so this is something worth finding out. This is only a small percentage of the population, but it also explains why some people respond with polarity to certain nutritional interventions compared to others.
Disadvantages of Carb-adaption
You need to eat frequently, like every 2-4 hours. If you miss a meal/snack, you’re cranky, foggy; all you can think about is eating. So you’re basically a slave to food. (I have seen exceptions to this, carb-adapted people that eat 1-2 times per day and feel fine, but that’s certainly atypical).
You have to be quite strict with taking in fewer calories than you burn, to the point of constantly tracking it. This is not to say that in other metabolic states calories don’t matter, because they do, but neuroendocrine signaling tends to take care of this for you in fat-adapted & particularly keto-adapted states, where you automatically tend to eat less without even tracking.
Once you stop being young, insulin sensitive, active, or you begin eating more calories than you expend, you’re fucked.
If you’re not genetically predisposed to efficient utilization of glucose at the expense of fatty acids, your blood lipids and risk of things like heart disease, diabetes, Alzheimer's, Parkinson's, cancer, and Shark AIDS will be increasing on the reg. Not saying you’re going to get these things (well, except shark AIDS, you’re definitely getting Shark AIDS), but if you’re going the carb-adapted route, just do yourself a favor and keep an eye on blood work. And not the bullshit labs your doc throws at you, but the real-deal stuff like NMR lipid testing.