In Rewriting The Fat Burning Textbook – Part 1 you discovered how eating a high fat diet doesn’t make you fat, and may actually increase the amount of fat you burn as fuel at both rest and during exercise, allow you to exercise or function for longer periods of time while eating relatively few calories, massively improve your health and not limit performance in the least.
But much of that information is theoretical, and not grounded in hard, sweaty numbers. Sure, there are videos such as this that suggest high-fat diets and ketosis-adapted performance can aid with things such as fat loss and high-altitude resilience, but there is scant data related to the pointy end of human performance potential.
However, what if we could actually prove that eating a low-carb, high-fat diet for a long time, becoming fat-adapted and even avoiding carbohydrates during the one time when we’re most encouraged to consume carbohydrates (during exercise)…
…could actually turn you into a fat-burning machine without losing a shred of performance capability or causing any metabolic damage?
That, my friends, would rewrite the fat-burning textbooks.
Let’s find out if it can be done…
Enter The Exercise Nerds: The FASTER study at the UCONN Human Performance Laboratory
As you’ve already learned – from controlling cancer to reducing your waistline to biohacking your brain – a high fat and low carb diet has been shown to massively enhance health, energy levels, and focus while reducing risk of disease. But what does a high-fat diet do to the body when you’re exercising? Does it actually cause you to burn more fat as fuel? Does it mess up your gut? Does it drain precious muscle and liver energy stores?
And most importantly: can you turn yourself into a complete fat burning machine without losing a shred of performance capabilities?
These are all complete unknowns.
Just several weeks ago – after following a strict high fat diet for 6 months – myself and a group of other fat adapted athletes walked into the prestigious Human Performance Laboratory at University of Connecticut for a battery of unpleasant tests that would answer these questions, including:
-defecating into a collection tray so that scientists can inspect how a high fat diet affects gut bacteria and microbes…
-running at an extreme incline on a treadmill until complete volitional fatigue while bleeding lactate out the fingertips…
-taking an X-Ray radiation scan for visualization of body fat mass and skeletal structure…
-having a cannula inserted to collect blood samples throughout a day of exercising to investigate cholesterol, triglycerides, inflammation, glucose and white blood cells……
-getting a biopsy needle jammed into the muscle to extract 200 milligrams of tissue, and another biopsy needle jammed into the butt to extract samples of fat tissue…
This will all culminate with a 3 hour endurance run sufferfest on the lab treadmill, while continuing to bleed into test tubes, salivate onto cheek swabs and breathe into a gas-analyzing mask.
The results will eventually be published in a scientific paper by high-fat diet guru and researcher Jeff Volek. But I’ve been given exclusive permission by UConn researchers to jump the gun and write an blog post about the entire experience and the results. In this post, I’ll provide everything: the gory photos, the lab rat details and most importantly, whether the average exercise enthusiast can really benefit from a high fat diet.
To make things easy to understand, I’ve broken the entire study process into 13 steps.
Let’s jump right in, shall we?
12 Steps To Turn Yourself Into A Fat Burning Machine and Prove You Don’t Really Need Carbs
Step 1: Follow A High Fat Diet For 6 Months
The UCONN study enrolled highly trained male and female ultra-endurance athletes (e.g. ultra-marathoners, Ironman triathletes, etc.) who have strictly consumed a low carbohydrate diet (defined as less than 20% of calories from carbohydrate) or a high carbohydrate diet (defines as more than 55% of calories from carbohydrate) for at least 6 months.
As you’ve probably guessed by now, I was one of the low carb guys.
In my article at “How Much Carbohydrate, Protein and Fat You Need To Stay Lean, Stay Sexy and Perform Like A Beast?”, I describe how to practically pull off a 20% or lower carbohydrate based diet. In another article, “The Great Ketogenic Ironman Experiment” article, I describe how to tweak a low-carb diet to go as low as 5% carbohydrate intake (also known as ketosis).
But in case you’re purely interested in the food porn, and how one pulls off a high-fat diet for 6 months without being married to a coconut milk subscription on Amazon, here are some sample staple meals I ate during those 6 months:
1. Beef bone marrow – one of the most nutrient-dense fat-packed foods on the face of the planet, photographed here with broiled carrots, onion and kale. Click here to read more about the wonders of bone marrow.
2. Eggs n’ avocados – this omelette, avocado and pitcher of olive oil were photographed on my hotel room bed the day I arrived at UCONN, about 24 hours prior to the onset of testing.
3. Smoothies – I travel quite frequently, and have found that hotel buffet breakfast bars often have blenders. In a case like this, I ask for things like an avocado, spinach or kale, coconut milk, butter, olive oil, seeds, and nuts, and simply have them dump it all into the blender. In a case like this, photographed at a hotel in Cancun, Mexico, the green slosh wound up in a bowl, topped with pumpkin seeds.
Is there potential for low hormones, low blood pressure or metabolic damage while following a strict low carbohydrate diet?
Step 2: Test Oxygen Utilization and Blood Lactic Acid
To set a baseline for the 3 hour treadmill run that was to take place the following day, I underwent one of the most brutally intense exercise science tests that exists: a V02max treadmill protocol. This was to me on the research study waiver as “a incremental treadmill test that will continually increase intensity until you achieve volitional fatigue”. In other words: I was expected to run until I would nearly pass out and fall off the back of the treadmill. After warming up, this test usually takes about 12 minutes, with significant increases in speed and grade every two minutes.
Before each two minute stage, I took a brief stop for needle-yielding researchers to take single drop of blood from my finger to analyze blood lactate concentration. Blood lactate is the gold standard for determining when your muscles begin to produce more lactic acid than they can actually remove. Blood lactate levels during exercise are also a parameter that’s never been measured during exercise in fat-adapted athletes. Since a fat adapted person is burning less carbohydrate, they should theoretically produce less lactic acid, resulting in less burn and less discomfort during exercise – a convenient biohack indeed…
For you physiology nerds – here is a .pdf download the VO2 Max Results. Notice the significant carbohydrate utilization only during the final two minutes of extremely intense exercise.
Step 3: 24 Hour Urine and Stool Collection
It’s known that your macronutrient ratios (carb/fat/protein ratios) drastically affect the bacteria in your gut, and that influences everything from neurotransmitter production to performance to propensity for obesity (hence the current pursuit of a bacteria-based “fat drug”).
So for this study, I was not only required to collect 24 hours of urine in a fancy, orange container (to strictly monitor hydration status, and also to measure nitrogen content of my urine)…
…but I was also required to poop in a yogurt-carton sized plastic container and hand in a stool sample so that the researchers could look at bacteria and microbes from my gut. The fecal samples will be used to analyze my microbiome using (and this exactly how it was described to me by the researchers) “next generation sequencing techniques which target the bacterial 16S rRNA gene”. Apparently this is very similar to type of testing being utilized by the fascinating American Gut Project.
Step 4: DEXA Scan
Believe it or not, those electronic scales you step on for body fat measurements can be notoriously inaccurate. Instead, the gold standard measurement for body composition (fat percentage, muscle percentage, and bone weight/density) is determined by using a machine called a “DEXA scanner” . That’s right: the same type of scanner used to diagnose osteoporosis can also tell you how fat you are. During my DEXA scan, I lay quietly and completely still on a table while a certified X-ray technician directed a scanning arm to pass over my body from head to toe, taking about 5 minutes to analyze my entire fat content.
You might be interested in the results you’ll find on the table below if you would like to allay any fears that a high fat diet will make you fat. I’m actually far leaner than when I was eating a low fat diet.
Warning: If you decide to get a DEXA scan to measure your own body fat, muscle percentage and bone density, you will be exposed to a very small amount of radiation by the scanner used to measure your body composition. Exposure to any amount of X-ray radiation, no matter how low, may cause abnormal changes in cells. However, the body continuously repairs these changes – and the amount of radiation is very low in just one DEXA scan The total exposure for the whole body scan is approximately 125 times less than the average radiation from a standard chest X-ray.
Here is a .pdf download of my DEXA results. Do you find it interesting that a 60%+ fat based diet still results in 5.2% body fat? Shocking, eh?
Eating fat doesn’t make you fat, folks.
Step 5: Muscle and Fat Biopsy
Now comes the fun part – a pre-workout muscle and fat biopsy to determine carbohydrate storage, and whether a high-fat diet has left me “carb drained”. In addition to measuring carbohydrate storage, the muscle analysis can look at how my fat-adapted muscles could support a theoretically larger-than-normal level of fat oxidation. The biopsy allows for measurement of muscle glycogen, triglycerides, fiber type, markers of inflammation and immunity, and even specific expression patterns for some genes.
Here is exactly how the muscle biopsy was described to me by the researchers:
“For this procedure you will lie down on a comfortable hospital bed before exercise. We will use a local anesthetic to numb an area of your skin and thigh muscle before obtaining a small amount of muscle via a muscle needle biopsy. This is the first of three muscle biopsies that will be taken, including one immediately after exercise and one two hours after exercise.
While Lidocaine does a good job of eliminating the sharp pain of an incision, it cannot fully eliminate the dull pain associated with doing the biopsy. The biopsy needle is about the same diameter as a Bic pen. After the incisions in the skin and fascia are made, the needle will be inserted through them into the muscle. The biopsy needle will likely cause the muscle to cramp for a second. Once in place, the needle will be used to make three or four “snips” in the muscle, which will be removed from you. The total amount of muscle removed will be between 50 and 200 mg, or a total amount about the size of an unpopped popcorn kernel. After this, the needle will be withdrawn, some pressure will be put on the site to control bleeding, and the incision will be closed either with one suture. You will not notice this muscle missing, either cosmetically or functionally. There are studies where more than 400mg have been removed without problems.
After the procedure, you will have a pressure dressing applied to the site and your thigh will be wrapped with a compressive wrap. It will be tight, but should not be painful. The night of the procedure, you will be instructed to keep your knee bent as much as possible, apply ice to your thigh, avoid heat or massage, and avoid anti-inflammatory medication.
It is vital that you understand that your thigh will hurt after a muscle biopsy. The pain you will feel will be like a deep “Charley Horse” and will typically improve over 48-72 hours. It is impossible to quantify the pain for you. Everyone's experience with pain is unique, and one's sensation of pain is influenced by multiple other factors than just the procedure itself. The exact same procedure, done the exact same way, will be felt differently by different people. It will even vary in the same person if they have multiple biopsies over time. There have been situations where people have hurt for more than a week. The more accurate expectation is 48-72 hours of tolerable aching in your thigh. After the first night, you will be allowed to exercise in any way you tolerate.”
Want the short version? They jam a needle into your leg, cut out muscle to freeze dry, and it hurts like a mother-f&*#er. Especially later that night.
The fat biopsy (AKA cheap liposuction) was relatively similar, and described to me as follows:
“Prior to each of the three muscle biopsy procedures, we will obtain a small piece of fat beneath the skin from the outer upper quadrant of the buttock under local anesthesia using a needle. The buttock area is chosen because the participants in this investigation are lean, and this area is likely to yield greater access to fat relative to other common sites (e.g., abdomen, quadriceps, etc.). A 16 G needle (about as thick as a penny) will be adapted to a syringe filled with sterile normal saline in order to apply suction. The needle will be inserted into the subcutaneous fat and the tissue will be “suctioned” by the syringe. The needle will be repeatedly inserted and retracted a couple of times in the fat layer to obtain at least 2 mg tissue (about a drop of water) up to about 100 mg (equivalent weight of a toothpick).”
Despite promises of just a toothpick size portion of fat, this one also hurt like a mother-f&*#er. All gory photo details below.
Step 6: Blood Draws
I’ve always been a big fan of self-quantification, and for the past 2 years have done regular blood testing via WellnessFX to track parameters such as “What Kind Of Damage Happens To Your Body After You Do A Hard Workout, Triathlon or Marathon?” and “What Happens When You Combine Low Carb and Extreme Exercise?”. So a fasting blood sample was nothing new to me.
But it was certainly a new experience to give 12 different three-tablespoon sized blood samples at multiple intervals throughout the day, including 4 times during a 3 hour treadmill run. By the end of the day, I felt like a pincushion, and had arms peppered with so many needle dots that I looked like a relatively fit heroin-addict.
For this study, the blood test was for basic health related blood markers such as cholesterol, triglycerides, glucose, insulin, and inflammatory markers, and white blood cells.
You can click here download a pdf blood testing results., which show typical results you’d see from an athlete or someone who exercises a lot: high BUN and high creatinine from muscle breakdown, high RDW (Red cell distribution width) and low alkaline phosphatase from constant turnover of red blood cells. These are not big red flags, but just a natural consequence of beating up the body day-after-day.
Step 7: Resting Metabolic Rate (RMR) Test
Your body burns a specific number of calories per day for vital organ activity, such as automatic functioning of your heart and lungs, nervous system electrical activity, kidney function, liver detox, digestion, hormone production, subconscious muscle contractions, and skin temperature. Your resting metabolic rate (RMR), is the total amount of energy you expend daily on these type of functions – without taking into account physical activity such as climbing a flight of stairs, exercising, standing up, sitting down, etc..
A resting metabolic rate test measures your carbohydrate and fat oxidation by calculating a number called an “Respiratory Exchange Ratio” (RER). Your RER is determined by the ratio of carbon dioxide (CO2) you exhale to oxygen (O2) you consume. The RER range for most living organisms ranges from 1.0 (which represents pure carbohydrate oxidation) to around or just below 0.7 (which represents pure fat oxidation).
In other words, the closer your resting metabolic rate RER is to 0.7, the more likely it is that you are fat adapted, and burning pure fat as energy. If you’re curious about where your personal numbers are at, you can pretty easily Google “Metabolic Testing NAMEOFYOURCITY” and find a test at local university, sports medicine facility or health club near you.
Below is a timeline of every RER measurement taken throughout the day of my test. Notice the column marked “RER” and the column marked “% Fat”.
Yes, you are reading correctly – from the beginning of 3 hours of hard exercise, all the way throughout, and 2 hours after, my body was at nearly 100% pure fat utilization, at one point dipping into values the machine couldn’t even calculate (eg. 105% fat burning and 115% fat burning at 1 hour and 2 hours after the run).
Fat burning machine status, achieved.
And what about burning of protein?
That actually can’t be measured via RMR test. But it can be measured via nitrogen content in urine, which is precisely what was able to be accounted for in my fancy orange urine container. Those results aren’t in yet.
Step 8: Cheek Swab
Next came the cheek swab, for which I was given a special tooth-pick like device to scrape the tissue from the insides of both my cheeks. Cheek cells can be used to look at membrane fatty acid composition and researchers have identified specific essential fatty acids that track closely with carbohydrate processing, free radical stress, and fat utilization – all from your mouth!
These results are also not yet in, but based on the other data, promise to be fascinating.
Step 9: Pre-Long Run Meal
This is a point in the study where things strayed a bit from what I actually expected. See, in a “normal” situation, if I knew I were going to be pounding the pavement or running on a treadmill or doing any other form of relatively demanding exercise for 3 hours, I’d have a hefty portion of fats a couple hours prior, such as my 1000 calorie ketogenic kale shake.
Like I mentioned earlier, even a lean human body like mine still has tens of thousands of storage calories of fat to burn – but that doesn’t mean I’m not a fan of mowing down a huge fatty shake, and I’ve actually made that a habit before big workouts.
Alas – prior to spending my personal record longest time on the treadmill, I received the following paltry 400 calorie smoothie, served out of a paper cup (ironically adorned with a Dunkin’ Donuts logo):
-1 tablespoon olive oil
-0.5 tablespoon walnut oil
-17g unflavored whey
-1 ounce heavy whipping cream
-2 ounces water
I sucked this pink aperitif down in a couple seconds flat, then waited a very long and nervous two hours to begin my 3 hour treadmill run.
Step 10: 3 Hour Treadmill Run
Now comes the fun part.
I must admit I was a bit apprehensive about running on a treadmill for 3 hours. Like most folks, I can run on one of those boring black belts for about 20 minutes before I feel like blowing my brains out.
And to make matters worse, the longest I’ve ever previously run on a treadmill is exactly 1 hour and 34 minutes.
In addition, I’m a “minimalist training” guy. This means I rarely train for more than 10 hours a week and rarely run for more than 60 minutes or more than twice a week, ever. Most of my Ironman triathlon “long runs” are 2 hours in length, and extremely few and far between.
So I experienced a series of emotions during my virgin foray into running while staring the blank white wall of a lab for 3 hours, including:
1. Elation and excitement. The journey has begun! It is time to become the ultimate lab rat!
2. Extreme boredom. Glancing at the clock. 7 minutes in. Damn. Must remember to avoid looking at the clock.
3. Extreme difficulty getting motivated to run again after stopping 30 minutes in for a blood measurement. Too bad I need to do 3 more of those during the run.
4. More boredom. Staring at the red square of tape on the wall and wondering why it’s there. Music and .mp3’s not helping.
5. Slight hunger pang as an intern walks into the room with a dozen donuts and two cups of coffee. Extreme avoidance of both carbs and caffeine seem to affect one’s appetite when extremely bored on a treadmill.
6. A sudden urge for a plasma screen TV and good movie at 1 hour and 30 minutes.
7. At the 2 hour mark, a realization I was far past 50%. Just 60 more minutes of chronic repetitive pounding.
8. A growing inability to avoid clock-watching. 2 hours and 9 minutes. Must stop looking at clock.
9. More elation and excitement. Close to 3 hours. Hope that my post-workout smoothie is bigger than 4 ounces.
10. Pride and relief. Three hours. 22 miles. Note the treadmill dashboard photo below to prove it.
The worst of it was two completely worn away toenails, some serious crotch chafing, and the constant throbbing on my quad’s biopsy wounds with each step. I’ve decided to spare you from having to view those photos.
Although the data on the run is going to be pouring in for weeks to come, I want to share some preliminary results with you in the photo and table below.
But first, a quick explanation of what you’re about to see.
In regards to fat oxidation during exercise, there are a huge number of papers that have examined fuel substrate use during exercise. Some of the more comprehensive work is by Asker Jeukendrup You’d be hard pressed to find any evidence that fat oxidation rates can be increased to anything above 1 gram per minute (g/min). Period. That is simply what scientific literature accepts as the top end of fat burning during exercise. And once again, it’s important to remember that all this literature and all these textbooks are based off studies on non-fat adapted athletes who did not eat a high-fat meal prior to exercise with no fuel during exercise.
So upon hopping on the treadmill while wearing the very same mask I wore during the resting metabolic rate test, I was naturally quite curious to see the amount of fat I was oxidizing after becoming fat-adapted by eating a high fat diet for 6 months and then a pre-run high fat meal.
And as you can see in the photos and table below:
-I consistently burnt far above 1g/min of fat during the entire run, and often went above 1.5g/min, which is unheard of (notice the -0.16 g/min carbs in the photo below…I was burning so much fat the carb count registered as negative)
-My RER during the 3 hour treadmill slog showed a fat burning level higher than most modern carb-consuming people burn at complete rest.
-During the majority of hard, sustained exercise, I was burning close to zero carbohydrates.
-I continued to burn nearly 100% fat and 0% carbohydrate for hours after the run.
In the words of Dr. Jeff Volek, the head researcher in the study who e-mailed me a brief synopsis a couple weeks after my run: “Even the weakest fat burners in our cohort are above this threshold, and in fact most are more than 50% higher.”
Consider the textbooks re-written.
You’ve already seen this graph earlier. I will once again highlight the RER column and the % fat column. My body is not really relying upon carbs while I'm exercising.
Step 11: Post-Long Run Biopsy, Meal and RMR Test
One of the key components of this study was to do another muscle biopsy as soon as I finished running (to see how much muscle carbohydrate I burnt through) then feed me a complete replica of my tiny pre-run “Single Strawberry Smoothie”…
…and finally wait another 2 hours for a final biopsy and metabolic rest test to assess rate of muscle carbohydrate repletion and how my fat burning rates responded to that post-workout meal.
These post-run steps would answer three simple questions:
1) How much carbohydrate do you burn through during a long workout if you are fat adapted?
2) Do you replenish energy levels just as well if you are fat adapted?
3) If you’re fat adapted, how much fat do you burn as a fuel in the hours after you finish a workout?
As you can see from the table above, and as alluded to earlier, I continued to burn fat at an increasingly greater level for hours after the workout (see Post-60 min and Post 120-min rows, and then check out RER, %Fat and %CHO columns).
As expected, my post-long run meal certainly didn’t throw me out of fat burning mode. When the muscle biopsy results are in, we’ll see how rapidly that meal restored glycogen, and whether I burnt through much glycogen at all – although I did have a great hotel-room suspension strap training session before I hopped on the plane the next morning, and noticed no sluggishness or lack of energy.
Step 12: Final Biopsy
Did my post-workout smoothie get absorbed any differently by following a high-fat protocol?
What kind of inflammation occurred in the muscle tissue? More or less by avoiding carbohydrates?
Was there truly evidence of increased fat oxidation on the muscular level?
The only way to find out would be to go back in for one third and final scalpel incision and needle biopsy. At this point, after pooping in a yogurt container, getting chunks of muscle and fat taken out of my thighs and butt, running three hours on a treadmill and give many, many tablespoons of blood, I was pleasantly numb to the pain.
I’ll prove it. Just look at my facial expression in the photo below.
As you can see from just the preliminary data and from Part 1 of this series, there is strong evidence that:
-Eating a high fat diet doesn’t make you fat.
-Eating a high fat diet can increase the amount of fat you burn as fuel at both rest and during exercise.
-Eating a high fat diet can allow you to exercise or function for longer periods of time while eating relatively few calories.
-Avoiding high carbohydrate intake improves health and doesn’t limit performance.
-Someone needs to tell the folks a UConn to get bigger smoothie cups.
From the muscle and fat biopsies to the urine and stool samples to the cheek tissue results, the data from the FASTER study at UConn will continue to pour in, and as it does, I will report back in the comments section below.
I’m also happy to reply to any questions you have about this lab test, the process of becoming fat-adapted, eating a high-fat diet, exercising with a low carbohydrate intake, or achieving improved body composition, better health, and superior performance by turning yourself into a fat-burning machine. Simply leave your thoughts, comments and feedback below…
…and if you really dig this stuff and want to learn more about exactly how to fuel, perform and recover with ideal ratios of carbohydrates, proteins and fats, read chapters 11 through 17 of my book “Beyond Training: Mastering Endurance, Health And Life”.