Fat Burners and Sugar Burners

Next week I have a camp here in Scottsdale, Ariz which focuses on getting the athletes started on their Base training with a solid plan. I also do this for each of the athletes I coach. Part of the procedure involves a determination of how the athlete's body prefers to fuel itself. This is a critical issue for long-distance athletes regardless of sport. So with this in mind I went back and dug up an article I wrote for a magazine on this topic a couple of years ago. You may not have seen it so here it is...

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Are you a fat burner or a sugar burner? Most athletes don’t know, yet this is valuable information, especially if you compete in four-plus-hour races. A limiting factor for such events is carbohydrate intake. If you don’t take in enough sugar during the race you are likely to run low which ultimately means your name in the results will be followed by the letters ”DNF” (did not finish). On the other hand, take in too much sugar and your gut can’t process it possibly resulting in bloating and nausea.

To further complicate the matter, there is a fair amount of individuality when it comes to using carbohydrate during such events. Some people’s bodies burn more carbohydrate as a percentage of total calories used. They are “sugar burners” and need to be very concerned with carbohydrate intake. The “fat burner” has a body that prefers to use fat for fuel and so spares sugar stored in the body. This person is metabolically designed for long endurance. That may be the result of fortunate genetics or effective training.

How do you know if you’re a sugar-burner or a fat-burner? And how do you determine if you are taking in the right amount of carbohydrate? Ultimately you need to experiment during your long workouts to find what works best for you. But you can narrow it down by discovering your “Respiratory Quotient” (RQ) which is sometimes also called the “Respiratory Equivalency Ratio” (RER). (They aren’t exactly measures of the same thing but close. You can read about RQ here and RER here.) Once you know your RQ rate you have a better idea of what your carb needs are during exercise. If you find you’re a sugar burner it may even be possible to change your body so that it relies more heavily on fat. More on this later.

RQ may be found by doing a metabolic assessment or VO₂max test. It used to be that you had to go to a medical clinic or university lab to have such a test done, but now there are boutique testing centers popping up around the country in health clubs, bike shops, and running and triathlon stores. You can probably find such a test facility somewhere near where you live. The test generally costs between $150 to $250. It can be done on your own bike using the test center’s indoor trainer (this is preferable to using a stationary bike) or on a treadmill for running. If you’re a triathlete and can afford only one test I’d suggest doing it on the bike as your nutrition here generally has a greater impact on your performance than when running due to the duration of the bike portion.

The typical test protocol starts you at a very easy effort and increases the intensity every few minutes until you fatigue and can no longer continue. In order to get good data you need to treat the test like a race by resting for a couple of days before. Doing this test tired will muddle the results and what you do with them.

There will be several pieces of information resulting from such a test. One is RQ. As the intensity of the test increases you will gradually burn more carbohydrate (glycogen) for fuel. The RQ closely estimates how much of the energy came from carbs and how much fat. The following table may be used to determine your percent of energy burned from these two nutrients throughout the test.

RQ	Carb %	Fat %
0.71	0.0	100.0
0.71	1.1	98.9
0.72	4.8	95.2
0.73	8.4	91.6
0.74	12.0	88.0
0.75	15.6	84.4
0.76	19.2	80.8
0.77	22.8	77.2
0.78	26.3	73.7
0.79	29.9	70.1
0.80	33.4	66.6
0.81	36.9	63.1
0.82	40.3	59.7
0.83	43.8	56.2
0.84	47.2	52.8
0.85	50.7	49.3
0.86	54.1	45.9
0.87	57.5	42.5
0.88	60.8	39.2
0.89	64.2	35.8
0.90	67.5	32.5
0.91	70.8	29.2
0.92	74.1	25.9
0.93	77.4	22.6
0.94	80.7	19.3
0.95	84.0	16.0
0.96	87.2	12.8
0.97	90.4	9.6
0.98	93.6	6.4
0.99	96.8	3.2
1.00	100.0	0.0

The fat-burner will start the test with an RQ of around 0.80 meaning that he or she is using about 33% carbohydrate and 67% fat for fuel. That’s good. I like to see that in those I coach. An otherwise similarly fit sugar-burner may start the test at the same low intensity but with an RQ of 0.90. At this RQ he or she is burning 67% carbs and 33% fat. That’s not so good. I see very few of these but they are out there. When both athletes reach their anaerobic or lactate thresholds they will be at about 1.00 RQ which means 100% carbohydrate and 0% fat. (Total fatigue will end the test at an RQ of about 1.1 to 1.2 for both.)

Notice that the sugar burner has a much narrower RQ range (0.90-1.00) than the fat-burner (0.80-1.00). So at moderate intensities, as are common in long-distance events, the sugar burner needs to be very aware of carbohydrate intake as he or she risks running low on this precious fuel. Some athletes are such gigantic sugar burners that they find it difficult to take in enough carbohydrate during the competition. They’re using sugar faster than their stomachs can process it from sports drinks. That often means a gut “shutdown.”

If you discover from a test that you are a sugar burner you may be able to modify this condition somewhat. I say “may” because there is some research indicating that there is an element of genetics involved [1]. This probably has to do at least in part with your muscle make up, especially your percentage of slow twitch or “endurance,” muscles [2].

Another chief determiner of RQ is your diet. Simply put, the more high glycemic load carbohydrate foods you eat (starches are the most prevalent in this category) the more your body will rely on sugar during exercise [2,3]. Conversely, the more fat and protein in your diet the lower your RQ will be. Eating starch or taking in glucose in a sports drink before the start of the test or the race may also shift your RQ to the sugar-burning side whereas fruit juice will not have this effect [4]. (Lesson: Best not to rely on sports drinks or starches before races.) The other known influencers of RQ are related to training. As you become more aerobically fit your RQ will drop [5], and related to that, research has shown that as your training volume increases RQ is also reduced [2].

It is even possible to determine how much carb you need to take in during a race from a test. All you need to do is find your goal race intensity—heart rate, power or pace—for your race in the test’s raw data results and determine, also from the results, how many calories you were burning at that point. Then check RQ at that same intensity to see what percentage of those calories came from sugar. You will need to replace most of this expended energy during long events (this is not a big deal for short races). The test technician can help you figure this out.

Knowing your RQ and, more importantly, keeping it on the low side through diet and training has the potential to improve your performance in long-distance endurance events.

 References

1. Toubro et al. 1998. Twenty-four-hour respiratory quotient; the role of diet and familial resemblance. J Clinic Endocrin Metab 83(8):2758-2764.
2.  Goedecke et al. 2000. Determinants of the variability in respiratory exchange ratio at rest and during exercise in training athletes. Am J Physiol Endocrinol Metab 276(6):E1325-E1334.
3. Hughson and Kowalchuk. 1981. Influence of diet on CO2 production and ventilation in constant-load exercise. Respir Physiol 46(2):149-160.
4. Decombaz et al. 1985. Oxidation and metabolic effects of fructose and glucose ingested before exercise. Int J Sports Med 6(5):286-288.
5. Kiens et al. 1993. Skeletal muscle utilization during submaximal exercise in man: effect of endurance training. J Physiol 469:459-478.

Comments

[Roberto]

Dear Joe,

Simply put: a superb post.
...as usual.
Regards,

Roberto from Chile

[Sheila]

Joe - So glad to see youu address this critical part of an athletes' training. As a Registered Dietitian specializing in sports nutrition I have seen first hand that this works. I provide metabolic testing in the Sacramento area. www.MyNutritionZone.com

[Pat]

Is it possible to test this on the road as opposed to a lab? Is there some kind of correlation between how long someone can sustain something like a zone 2 or 3 power output without any caloric intake and the percentage of fat their body is metabolizing? It would be neat if I could go for a long ride, and see after that my power dropped off at a given point and then find that that correlates to a particular RQ...

[Joe Friel]

Hi Pat--Thanks for your comment. No, there really isn't a way to do a field test for RQ short of seeing how long it takes for you to bonk at a given intensity.

[Laura Wheatley]

Joe- I echo Sheila's thoughts. Of all the metabolic and fitness assessments we can do in our lab (Illinois State University), I feel that the results from our "FUEL" test are the most useful for endurance athletes. Athletes walk away from this test with custom training/race nutrition plans, and a better understanding of their "metabolic efficiency" during exercise.

This is also a great assessment for those seeking weight loss through exercise - by looking at the fat/carbohydrate breakdown, we can determine the optimal intensity for "fat burn" as well.

We provide this assessment at the Illinois State University Exercise Physiology Lab- open to the public! It costs $100. Check out our website at http://kinrec.illinoisstate.edu/lab/service/
or contact me: lavedee at ilstu dot edu

[Ted]

Joe, I have a client in the Portland, Maine area (an orthopedic practice with a performance center) that would be interested in having you speak on this topic. How can I best contact you to provide you with the details?

Ted Darling
tdarling@ethos-marketing.com

[Hans]

Hi Joe, thanks for a great article and many great books.
I did a VO2 max test a couple of years ago (running on a threadmill).
I then got a RER of 1.16 (My VO2 max was 60.3)
What can i read out of my RER number?

Best regards
Hans from Norway

[Joe Friel]

Hans--Almost everyone stops the test between 1.1 and 1.2. So your 1.16 tells us that you are normal in that regard (for an athlete). It's how fast RER ramped up early in the test that tells the story.

[Cookie]

Interesting post Joe.
I switched loosely to the "Primal Blueprint diet" about 6 months ago so my body could learn to utilise fatty acids more effectively. Just 2 weeks ago I competed in the World 24 MTB solo event and feel it was a key to my performance and enable me to ride 24hours with minimal stops.
I will say that changing your diet lifestyle can be tough initially as "my" body was programmed to need the sugars. My cravings were bad for a few weeks but now I find so much stuff overly sweet. Its good to not need all that sugary stuff (gels) on long road rides etc.

cheers!

[Paul]

Hi Joe,

Thanks for the post, really great information! So what is the prognosis for a sugar burner for long distance -- Ironman or ultra runs? Can a sugar burner still excel at these events?

Thanks again!
Paul

[Joe Friel]

Paul--Being a sugar burner is one strike against you before you even start. Trying to stay fueled becomes more challenging--not impossible. Just more challenging.

[Ron Arroyo]

Great info Joe thanks for hitting this topic it's easier for me to print out your explanation than for me to try to explain it. We are team testing at bike ranch the 13th and 14th if you are in town stop by.

Thanks again,

Ron A

[wayne]

Great articule Joe - I have recently done a couple of ramp tests and got the RER results along with figures for how much carbs and fat I was burning in each target training zone (the training zones were provided as well). In summary I started with a RER of 0.91, which makes me a carb burner based on your article, but in the training zones my recovery zone has me down as burning .12 grams of carbs and 1.12 grams of fat. In my endurance zone it was .8 vs 1.16 carbs vs fat. Are these results consistent?

[Dani]

Great info, very in depth

I'd never really considered how much sugar I was taking in but the bloated and nausea feeling is familiar, maybe I should cut back

[burner]

Almost everyone stops the test between 1.1 and 1.2. So your 1.16 tells us that you are normal in that regard (for an athlete). It's how fast RER ramped up early in the test that tells the story.

[cholesterol lowering diet]

I have stumbled upon your blog and this post is exceptionally informative. My friends told that by having the right food and exercise will help. I have always been thinking of lowering my cholesterol level through biking as I like to ride on bike. Do you think it will help? Does fat burning help to lower my cholesterol level?

[Joe Friel]

Cholesterol--Adequate levels of exercise through activities such as endurance cycling tends to raise HDL ('good' cholesterol) and lower LDL ('bad').

[deri ceket]

Great info Joe thanks for hitting this topic it's easier for me to print out your explanation than for me to try to explain it. We are team testing at bike ranch the

[Victoria sallas]

I really enjoyed the info.i have been running for a year.i ran my first marathon in march.during training I found using 2 accelerade gels worked.i felt as if I needed more and more carbs.i wasnt losing any more weight despite all the training runs.so I decided to do the paleo diet fo athletes and started really trimming up.i also modified it to my schedule ,more calories for my biking swiming and running.it takes some tweaking and good info from other athletes.best in health,vy

[Ole Cyclist]

Hi Joe!

Very informative! I'd barely thought about this. I have three questions.
1. For how long races is this information adequate?
2. So, if I am a fat burner, what should I eat during long races?
3. Will a fat burner be as fast as sugar-burners on shorter events?

[dinle]

Great info Joe thanks for hitting this topic it's easier for me to print out your explanation than for me to try to explain it. We are team testing at bike ranch the 13th and 14th if you are in town stop by. thankss

[Joe Friel]

Ole Cyclist - The longer the event is the more important it is for your body to preferentially use fat for fuel. Short events (let's call that those lasting less than an hour) are not limited by fuel type. Of course, there are always individual exceptions such as extremely low aerobic fitness or depleted glycogen stores from previous extensive exercise.

[Rachel Peacock]

Joe,
Great info! But I am really interested in knowing what to eat before a short race or during a long race, as a fat burner. Please share! Thanks!

[Joe Friel]

Rachel Peacock - That's a short question but takes a very long answer--as in a chapter in a book. There are so many "it depends." I'd suggest you read my book, The Paleo Diet for Athletes. Available at Amazon.

[Amateur]

I did a VO2max test at my school, but for confidential reasons I'm not allowed to have the data. Anyway I was able to determine that I had an RER of 1.0 at an HR somewhere around 185-186bpm and an RER of 1.11 at 193bpm. Would these values correspond with AT and LT thresholds fairly close? They don't do lactate testing. Max HR which probably isn't important I think I got 202bpm.