One of the fitness indicators that we hope to improve in the Base period has to do with using more fat and less glycogen (carb) for fuel during long endurance events. As your body becomes better at using fat to produce energy essentially your aerobic fitness improves. This is especially important for very long, steady-state events such as half- and full-Ironman triathlons, century rides, marathons and the like.
I once coached a triathlete whose fat metabolism was so ineffective that he would have had a hard time finishing an Ironman. This was discovered during a VO2 max test by looking at his Respiratory Exchange Ratio (RER). (You can read more about this topic in a previous blog post. ) He would not have been able to take in and process enough sugar to keep the engine running that long without going very slowly. He was by far the worst athlete I’ve ever seen when it comes to fat burning.
So what influences your ability to use fat during exercise? There appear to be several. Here they are.
• Genetics. I’ve never seen any research to confirm this, but it stands to reason that how well we do at preferentially using fat for fuel must be some how related to our parents. This could be as simple as how much type I (slow twitch) muscle we have, to perhaps how abundant our aerobic enzymes are and probably many other variables. Unfortunately (or perhaps fortunately) it’s too late to do anything about this. You have what you have. Life isn’t always fair.
• Training. There are several studies and reviews that support the notion that endurance training causes a shift in metabolism toward greater usage of fat for fuel [1, 2, 3]. Trying to nail it down any tighter than that to what type of training is most effective is pretty complex. The research here is not in agreement. For example, one review of the research suggests that training below 75% of VO2 max is the best way to become a fat burner [4]. Another review suggests it’s even lower than that – 59-64% for trained athletes and 47-52% for sedentary subjects [5]. But to further muddy the water a third found that untrained subjects doing 4-minute intervals at 90% of VO2 max, 3 times a week for 6 weeks saw significant improvements in fat burning [6].
This is a critical area for athletes, especially in the Base period, so I’m currently doing an experiment with n=1 (me) to see how various chronic training intensities may affect RER. It’s a 5-month project which I’m only 2 months into. But I’m seeing some interesting results already. I’ll share them with you when it’s done.
• Pre-Exercise meal. Most of the research shows that if you eat a high-fat meal before exercise (as opposed to high-carb) endurance at low-intensity improves but high-intensity usually suffers [7, 8, 9, 10]. The bottom line here is that if you eat a lot of carbohydrate before a workout your body will have little need to use fat as a fuel. It’s probably best when doing workouts that are short (for ssome numbers to perhaps give you a reference, let’s say that means less than 3 hours on the bike, under 2 hours of running, or shorter than 90 minutes of swimming) and fully aerobic (below threshold) to eat a low-glycemic-index (LGI) meal or snack prior to the workout. LGI means foods high in fat and/or protein, some fruits (apples, peaches, pears) some grains (rye bread), legumes (soy, lima beans, lentils) and others. Such a meal or snack eaten no less than 2 hours prior to exercise will encourage your body to rely more on its fat stores thus improving metabolic efficiency.
There are lots of variables that go into how much you eat pre-exercise and how long the workout is. How much depends on when your last meal was, how much you ate and what you ate. The suggested workout durations above are more likely to work for experienced athletes who train a lot (more than 12 hours per week, perhaps).
• Pre-Exercise fasting. There is some research suggesting that fasting before a workout causes the body to use more fat for fuel during exercise thus training it to become more metabolically efficient [11, 12]. This may or may not be a good idea for you. I would definitely not recommend this before very long workouts (relative to what you are well-trained for). The risk of bonking could be very high. I think a better option is to eat a LGI meal a couple of hours before the workout and then use water only during shorter exercise sessions. As with fasting, I think this would cause the body to become better at using fat for fuel. But again, how long the workout is that you use water only is determined by the individual. Your shortest workouts should not be a problem at all. The question has to do with at what duration you use sports drinks, bars, gels, blocks or whatever. The suggested durations under “Pre-Exercise Meal” above may help you decide here. Regardless, when doing any length of workout it’s a good idea to have sugar handy, such as in a back pocket – just in case. Better safe than sorry.
• Chronic diet. Most studies show that chronically (for several days, weeks, months or perennially) eating a diet that is low glycemic index (some day I will write about the difference between this and “glycemic load,” which is probably a better standard but less understood) causes a shift in metabolism favoring the use of fat for fuel [13, 14, 15, 16, 17]. This is what Loren Cordain, PhD and I suggest in our book, The Paleo Diet for Athletes. It’s the type of diet the athletes I coach follow and it nearly always produces good results. I should point out that not all of the studies listed here show better performances – only improved fat utilization. I’ve come across only one study that found no improvement in RER with a low LGI diet [18].
Conclusion. There are four options suggested here to improve your body’s capacity for using fat for fuel (changing genetics isn’t an option – yet). No one knows for sure, as I suspect this has never been studied, but I believe the most effective are your chronic diet and training. I’ll have a bit more to say about training in a few months after I complete my semi-scientific, personal study. Until then I’d suggest that training in zones 2 and 3 are probably the most effective for improving fat utilization through training.
References
1. Askew, E.W. 1984. Role of fat metabolism in exercise. Clin Sports Med 3(3):605-21.
2. Gollnick, P.D. 1985. Metabolism of substrates: Energy substrate metabolism during exercise and as modified by training. Fed Proc 44(2):353-7.
3. Martin, W.H. 3rd. 1996. Effects of acute and chronic exercise on fat metabolism. Exerc Sport Sci Rev 24:203-31.
4. Holloszy, J.O., W.M. Kohrt, P.A. Hansen. 1998. The regulation of carbohydrate and fat metabolism during and after exercise. Front Biosci 3:D1011-27.
5. Achten, J., A.E. Jeukendrup. 2004. Optimizing fat oxidation through exercise and diet. Nutrition 20(7-8):716-27.
6. Perry, C.G., G.J. Heigenhauser, A. Bonen, LL.L. Spriet. 2008. High-intensity aerobic interval training increases fat and carbohydrate metabolic capacities in human skeletal muscle. Appl Physiol Nutr Metab 33(6):1112-23.
7. Wu, C.L., C. Williams. 2006. A low glycemic index meal before exercise improves endurance running capacity in men. Int J Sport Nutr Exerc Metab 16(5):510-27.
8. Vukovich, M.D., D.L. Costill, M.S. Hielly, etc al. 1993. Effect of fat emulsion infusion and fat feeding on muscle glycogen utilization during cycle exercise. J Appl Phsyiol 75(4):1513-18.
9. Okano, g., Y. Sato, Y. Takumi, M. Sugawara. 1996. Effect of 4h preexercise high carbohydrate and high fat meal ingestion on endurance performance and metabolism. Int J Sports Med 17(7):530-4.
10. Griffiths, A.J., S.M. Humphreys, M.L. Clark, et al. 1994. Immediate metabolic availability of dietary fat in combination with carbohydrate. Am J Clin Nutr 5(1):53-9.
11. Montain, S.J., M.K. Hopper, A.E. Coggan, E.F. Coyle. 1991. Exercise metabolism at different time intervals after a meal. J Appl Physiol 70(2):882-88.
12. VanProeyen, K., K. Szlufcik, H. Nielens, M. Ramaekers, P.L. Hespel. 2010. Beneficial metabolic adaptations due to endurance exercise training in the fasted state. J Appl Physiol [epub].
13. Staudacher, H.M., A.L. Carey, N.K. Cummings, J.A. Hawley, L.M. Burke. 2001. Short-term high-fat diet alters substrate utilization during exercise but not glucose tolerance in highly trained athletes. Int J Sport Butr Exerc Metab 11(3):273-86.
14. Goedecke, J.H., C. Christie, G. Wilson, S.C. Denis, T.D. Noakes, W.G. Hopkins, E.V. Lambert. 1999. Metabolic adaptations to a high-fat diet in endurance cyclists. Metabolism 48(12):1509-17.
15. Lambert, E.V., J.H. Goedecke, C. Zyle, K. Murphy, J.A. Hawley, S.C. Denis, T.D. Noakes. 2001. High-fat diet versus habitual diet prior to carbohydrate loading: Effects of exercise metabolism and cycling performance. Int J Sport Nutr Exerc Metab 11(2):209-25.
16. Hawley, J.A., F. Brouns, A. Jeukendrup. 1998. Strategies to enhance fat utilization during exercise. Sports Med 25(4):241-57.
17. Burke, L.M., J.A. Hawley. 2002. Effects of short-term fat adaptation on metabolism and performance of prolonged exercise. Med Sci Sports Exerc 34(9):1492-98.
18. Roltsch, M.H., J.A. Flohr, P.B. Brevard. 2004. The effect of diet manipulations on aerobic performance. Int J Sport Nutr Exerc Metab 12(4):480-9.
Interested to see how your research goes. I've always wondered whether skipping intervals all together was a good idea during base. I can't see the harm in 1-2 per week sprinkled in at moderate intensity.
Also, the references at the bottom of the post is why we all look to you for good solid info Joe. Thank you for your professionalism.
www.catskillscycling.com
Posted by: Michael Wentland | 01/03/2011 at 11:51 AM
thanks Joe. BTW, where does efficiency fit into the equation? Doesn't zone 2/3 work improve your efficiency thus reducing the effort required to perform at a particular speed /pace?And then would training/racing at the lower intensity burn more fat than carbs ?
Posted by: neeraj | 01/03/2011 at 09:56 PM
Hi Joe
I just read Jonas Coltings new book on health. Jonas is a well known triathlete around the world and a "health-guru" in Sweden (were I also live).
He argues that fasting is a good thing, for many reasons:
1) Your insulin levels drops significantly
2) Your energy level becomes steady
3) Fatburning increases (especially when the insulin level is low)
4) weight loss
5) Human growth hormone (hGH) secrete in higher levels. He calls this "human/natural doping"
6) You break a habit of always wanting food (especially sugar).
7) Your digestion get to rest and blood is directed to other parts of your body
He recommend a 24-36 hour fasting every third or fourth week, and that you do a short interval session at the end of the fasting period. He is also pro-paleo.
So my question is if you are as positive to fasting as he is?
Keep up your excellent work and writing!
/Anders
Posted by: Anders | 01/04/2011 at 01:09 AM
Anders--Sounds interesting. I have no experience with it and never seen research that addresses these points. Thanks for your post.
Posted by: Joe Friel | 01/04/2011 at 05:15 AM
Neeraj--The more efficiently you move the fewer total calories you burn at any given intensity. And yes, an improvement in efficiency would theoretically increase fat burning. Good point.
Posted by: Joe Friel | 01/04/2011 at 05:17 AM
As an amature , I can say that one reason for not burning fat so well, is the fear of the bonk. I had one bonk that was a dreadful experience, very close to home, and the world went topsy turvy. For the next 6 months I was drinking those carb loaded sugar loaded vitamin loaded drinks that are aimed at all of us sports types. I realised that even though my training was increasing, so was my weight. It was on a 3 hour ride, when I had 2 litres of sports drink on the bike, and a couple of gels in my back pocket, and bars, that I noticed the lean guy beside me had one tiny bottle. It had watered down grape juice in it. I thought about this. I went home and read. I realised that being 6kg over weight I didn't need to drink 500mls in a hour of swim training when I was getting thirsty. Water fine, even with a big of sugar or an isotonic tablet perhaps but certainly not the full energy replacement drinks. Once I cut back on those, I noticed a significant difference.
Posted by: Collie | 01/04/2011 at 05:59 AM
Joe,
According to Mark Allen, he made the leap into Ironman history by dropping the high intensity regime until after he had maxed out his base training (months of workouts at or below his aerobic threshold). Noakes even mentions in his book Lore of Running, that this approach to training is rarely used by many athletes and might also explain how Allen sustained his success for so long.
http://www.duathlon.com/articles/1460
Chuckie V echoed the same sentiments in his blog about how the body responds to high volume low intensity running (55% max V02). http://chuckiev.blogspot.com/2007/08/hadds-approach-to-distance-training-run.html
From what I've read, the goal of training is to signal to your body the need to build mitochondria, slow twitch fibers, and blood vessels. These components are the basis for improving the conversion of oxygen and fat into ATP. Diet, recovery, age, and genetics all play a part, but they each play a complimentary role to the base which is training. Or perhaps I have it wrong and the order varies based on the individual as some athletes have different genetic limiters and their training must reflect those limiters?
So I guess my question is that the key to becoming a fat burning machine different based on the individual, or is this more of a one shoe fits all process. That despite our genetic variation, all athletes would benefit from "X" style of base training?
Posted by: Travis | 01/04/2011 at 05:54 PM
Travis--Some will benefit more from base training--esp those who are new to intermediate level. Highly experienced elite athletes will reap less of a reward.
Posted by: Joe Friel | 01/04/2011 at 08:07 PM
Curious what the "worst ever" athlete's numbers were? My fat burning is also poor. My last test showed RER above .9 and 50/50 %CHO/%FAT at ~66% of VO2 power and uptake (35.8 against a max of 60.2). Being a masters bike racer and 10k runner, this doesn't hurt me so much, but I can't "ride off" weight so easily either. I theorize that I've been too diligent about post-workout glycogen replenishment and thus "trained up" my glycogen stores to very high levels. Since you did not mention post-workout routines as a factor, I thought I'd ask. Thanks!
Posted by: Dave F | 01/06/2011 at 05:13 AM
Why would you suggest training in zones 2 and 3 to improve fat utilization? It seems most studies agree that the most efficient fat burning heart rate is below 75% of VO2 max... wouldn't this be HR zone 1?
Posted by: Jay | 01/06/2011 at 03:11 PM
Interesting study about the benefits of training in a fasted stated compared to fed state (eating a meal). Training in a fasted state resulted better ability to use fat during the exercise.
Karen Van Proeyen, Karolina Szlufcik, Henri Nielens, Monique Ramaekers, and Peter Hespel. Beneficial metabolic adaptations due to endurance exercise training in the fasted state. J Appl Physiol 2011;110 236-245
http://jap.physiology.org/cgi/content/abstract/110/1/236
Posted by: Jaakko Mursu | 01/14/2011 at 09:03 AM
Joe, Its pretty common knowledge about the "fat burning" zones and most gym trainers go on about it. What my question is, if you are a very low % bodyfat person will training at high/er intensities lead to a loss in muscle mass above and beyond the fat burning amount? If so, what would fueling before and during offset that?
thanks
Posted by: cookie | 01/14/2011 at 04:01 PM
Cookie--Even the skinniest endurance athlete has plenty of fat to fuel a workout of any duration.
Posted by: Joe Friel | 01/15/2011 at 03:51 AM
Some points in your outline about fat need clarification, Joe:
Its a myth that the body will slowly adapt to fat burning when deliberately shifting the ratio from carbs to fat. Also its a myth that omega fatty acids such as from fish can be used as a major source of energy in human beings although some dietary experts may want us to believe this.
Instead, what it takes is an abrupt halt to ingesting carbohydrates and a special diet based on certain triglycerides and cholesterols to successfully switch to burning fat without leaving any counter-productive residues such as ketones in your body. For an athlete it is of utmost importance that he goes through a process of 100% sugar/starch deprivation until his body will accept metabolising fat and its by-products efficiently. Once done that its a mighty tool for any sports longer than an hour. Since 1998 I publish and conduct a form of fat diet labelled CREAM DIET many long distance athletes took successful advantage of. That's why I dare to say that no, switching to fat metabolism should exclusively be done under the guidance of a skilled practitioner, a naturopath or someone at least trained well in the field of medicine. Reason? Because many residues of former medication store in our fat tissues Now they come up soon his owner decides to diminish his percentage of body fat. Old symptoms may occur and unless they don't get properly re-treated they may cause unwanted side effects such as Collie referred to in his post which can make fat burning a rough trip rather than a mighty tool for anyone performing at sub-threshold for a prolonged period of time. Should you want to obtain more information and deeper insight in the art of fat training don't hesitate to get back to me under: info@biomac.biz
Götz Heine
naturopath
Posted by: Götz HEINE | 01/26/2011 at 10:25 PM
Goetz--There's an old saying in science that may apply here... "In God we trust. All others must provide data."
Posted by: Joe Friel | 01/31/2011 at 03:50 AM
Hi Joe,
why don't you get yourself a volume and gas sensor the type available on the fitness market. Experiment with it and you will soon find out that what I state is valid. To prove what I state I do offer you a 10-day course you can do from home and you will see it works very well - like all my ideas and recommendations so far.
Your's in Sports physiology,
Götz
Posted by: Götz Heine | 11/03/2011 at 06:45 AM
Hi Goetz--I'm afraid my memory fails me. Could you please tell me again what it is you propose as far as diet? And, secondly, provide any data to support it. Thanks.
Posted by: Joe Friel | 11/03/2011 at 09:39 AM
Cream, whipped cream it is. I published the diet ín few words on my site. Like when we met in Phoenix in 2006 I do this diet once a year. Remember I didn't drink and had no food with me. During the diet my body fat drops below 10% and after a recovery of two weeks I start flying.
As a result of the Cream Diet an athlete stays notably longer in fat burning zone, produces significantly less lactic acid in comparison to before the diet, sweats less, his ketone production is close to if not at zero and his ability to exercise without getting hungry is increased. I stopped monitoring lab data as the process became so familiar but I can ask athletes who went on the diet recently whether they want to share insight in their improvements.
Posted by: Götz Heine | 11/04/2011 at 03:30 PM
Hi Joe,
I read with interest your Blog and messages
from Götz.I recently competed in the Race around Ireland considered the 2nd toughest endurance Race in the world after RAAM. I was very kindly helped by Götz HEINE. I completed the Cream Diet and still trained with a reduced Volume of about 50 percent for about 10 days.I had a skin fold test done prior and about 2 weeks after the diet. Not that I need one as the mirror told me every thing I needed to know. I went from 12 percent down to 7 and a half percent body fat. I did a pre and post power test and no loss of power. I went on to compete in the RAI with using a diet of cheese,nuts, fruit,and dark chocolate. I have since had a full medical with blood tests and all is normal. I think this is enough evidence to support this theory. I also trained and raced using the mid cleat shoes that I bought from Götz.The Diet works try it for your self!
Posted by: Jim Doyle | 11/04/2011 at 04:56 PM
Hi Joe,
I read Gary Taubes' book and started following his dietary guidelines. We are training for a multi-stage endurance race (Cape Epic) with long hours in the saddle. My experience is that the body runs very well on fat provided you remain aerobic. I am amazed at how little one needs to eat and still remain strong and full of energy. It is obviously a complex issue with each of us reacting differently, but I would say it is worth trying going onto a low carb diet and trying to get your body to run on fat for long multi-stage events.
Posted by: Jean Hubert | 02/06/2012 at 10:24 AM
Jean H--Yes, diet certainly has the potential to shift metabolic RER to a lower value for any sub-threshold intensity. Eating starch and sugar only at the right times is the key to this. I haven't read his bok but if that's what he's saying then we're on the same page. Good luck!
Posted by: Joe Friel | 02/06/2012 at 02:53 PM
I would say that the relationship between VO2 max and fat-burning is the single most controllable, and therefore most important aspect, to any fitness program intended to assist with weight loss. My two cents....
Posted by: Mark Lorie Fitness | 04/05/2012 at 05:34 AM
Hi Joe,
Just wanted to write and say that I completed Gotz Heine's cream diet about 4 months ago. Since then my carb intake is absolutely minimal, I can go for 4 hour mountainous group rides with my mates and now win where I used to get a kicking. I consume considerably less water on rides, no carb drinks, bars or gels only fruit. My weight has gone from 79 kgs to 72.5 kg and bodyfat down from 18% to 8% . In short I have never felt belter on and off the bike. This may go against the common modern thinking of endurance athlete fueling however, for those of us who have now converted we know there exists other options.
Cheers and love the blog.
Christian
Posted by: Christian | 05/01/2012 at 09:44 AM