For those of you who are totally lean, terrific fat burners and never have any GI issues, stop reading this article. But for those of you who want to become, in the words of former fitness expert Covert Bailey, a “better-butter-burner,” read on.
This is not new science, but could be considered reemerging science. The Crossover Theory has been around since the 1930s and in the 1970s and 1980s, there was a large amount of research on aerobic training in relation to fat burning. High mileage weeks and long, slow, distance training was the norm. It wasn’t until later that quality became the standard in training over quantity. And with higher speeds (intervals) and constant “hammering” in training, the need for more immediate carbohydrates (aka immediate energy) brought about enormous developments in the sports nutrition product industry. Hence was born the carb-driven ultrarunner.
So, what’s wrong with carbohydrates? I personally have been writing and encouraging athletes to include plenty of healthy carbohydrates (whole grains, fruits and vegetables) in their training diets and recovery snacks for years. Nothing is wrong with carbohydrates; we just may have lost sight of one of the most important parts of our nutritional training…the BASE training. Metabolic efficiency guru Bob Seebohar says, “What puzzles me as a coach and sport nutritionist is that athletes do not put in half as much effort planning their nutrition as they do constructing their training plan. Why is this important? For the simple reason that the best training plan is worthless if the nutrition plan fails.”
Signs that your plan may not be working can be anything from GI distress (bloating, cramping, vomiting) to poor recovery and fatigue to out-and-out bonking. Ever suffered from any of these? Read on.
“Efficiency” is usually thought of as doing something well with the least amount of effort. One definition is the “measure of a machine’s energy effectiveness.” In ultrarunning nutrition, this boils down to being able to use more fat for energy while using less carbohydrate for energy. Why would we want to do this? Because at any given time, most trained runners are carrying about 1,500 – 2,000 calories of carbohydrates and 80,000-plus (!) calories of fat. (Even the leanest runners.) Yes, we need carbohydrates to activate fat-burning enzymes to burn fat for energy, but think of it this way: One fat-burning enzyme burns a little fat; a bunch of fat-burning enzymes ignites a bonfire. Metabolic efficiency training builds a stockpile of fat-burning enzymes. Voilà – the ultrarunner becomes much less reliant on consuming mass amounts of carbohydrates during the race and has less chance of GI distress.
What Is Metabolic Efficiency Training?
Sometimes it is easier explaining something by explaining what it is NOT. Metabolic Efficiency (ME) training is not a calorie-deficient diet and it is not a low-carbohydrate, Atkins-like diet. It is rather macronutrient partitioning – or manipulating your macronutrients (carbohydrates, fats and proteins) – AND exercise adaptation – or manipulating your exercise with correct aerobic training – that allows us to reap the benefits of increased fat utilization.
To do this, we need to understand the cross.over concept and learn our own crossover point. By effectively manipulating our aerobic training, we will increase mitochondrial capacity (the number of mitochondrial enzymes). By manipulating our diet to control blood sugar and our insulin response, we will be able to fuel with fewer calories during training and racing, thereby reducing our reliance on consuming simple sugars and increasing utilization of our internal body fat.
According to Seebohar, “This will benefit any athlete in any sport of any duration both in the short- and long-term.” Powerful, but the key is that you must manipulate both diet and exercise together.
How long does it take to become more efficient at burning fat? Results can happen in as little as four weeks. Most protocols are six to 10 weeks. You may want to start every season with an ME base when you experience the results.
The Crossover Concept
The crossover concept describes the relation.ship between exercise intensity and the use of fat and carbohydrate for energy during that exercise. Even though we burn a mix of both carbohydrate and fat to fuel exercise up to maximal intensities, as the intensity of your exercise increases, your body prefers to use more carbohydrate for fuel. There are several biochemical mechanisms contributing to this increased use of carbohydrates that are beyond the scope of this article, but suffice it to say, these mechanisms decrease your fat oxidation or usage.
The crossover point – that intensity at which you start to burn more carbohydrate than fat -can be measured or defined in terms of speed, pace, watts (if cycling) or heart rate. This gives you -the ultrarunner -a pace or heart rate to train below in order to increase your fat-oxidizing capacity (i.e. become a better fat burner). In the chart below, this crossover point occurs at 65 percent of VO2 max.
By wearing a heart rate monitor during an ME test, you can accurately correlate your cross.over point to your heart rate at that time. The goal of improving ME training is to “push the crossover point to the right,” in other words, to teach your body to use more fat (and therefore less carbohydrate) at higher intensities (higher heart rate). How do you teach your body to do this? Read on.
Exercise Training – The 30 Percent Effect
ME training lets your body use fats and carbohydrates more efficiently. It manipulates cellular processes through aerobic training by increasing the size and number of mitochondria in your cells.
So? Turns out that if you also continue this aerobic exercise without a lot of available carbohydrates, your body adapts by increasing its workforce of enzymes that metabolize fat (that “stuff” around your middle…) for energy. Ahh! So that’s why we want an aerobic base.
Many ultrarunners ignore or “skip over” setting up an aerobic foundation because we don’t see the immediate benefits as we do in speed training. This is not to say that interval training or hill repeats do not produce positive changes – they do – they just don’t improve fat burning. You will be more metabolically efficient if you work on fat-burning (aerobic exercise) first, and then add in the other training regimes.
Of course, you can get around this by relying on a constant source of carbohydrates coming in to fuel your muscles (aid stations, carrying lots of calories, spiking your insulin by eating simple carbohydrates…all the time) but you will still be carrying around some of that fat in your body.
Think of it this way: you know what goes through your mind when you see a runner carrying two full bottles of water during a race that they never drink, “Why carry all that weight around if they don’t use it?” Hmmm. Exactly.
So now after our ME test, we have our heart rate (or pace) to stay under. This may be hard, training at these lower intensities – believe it or not, when you are not metabolically efficient, it is easier to run at a higher heart rate – but it is very important to stay at the lower intensity to induce the cellular responses. This means a 10-mile run may take you two and a half hours because when you get to a hill, you will probably need to walk. Keep tabs on your heart rate.
Frequency is the key to ME training. You will need at least six to seven hours per week in this zone for results, but it is critical to have most of your training in this zone. Most of you are exercising a lot more than six or seven hours each week. This means that you can take one day a week off from ME training and run intervals or your regular group run, allowing your heart rate to exceed your ME training intensity, but your results will be delayed a bit. Remember, we are not talking about that long – you can see results in four to 10 weeks.
Implementing The Nutrition Plan – The 70 Percent Effect
The nutrition component has by far the biggest effect on your fat-burning capacity and it is here that you must make changes to your diet to see results. The bottom line is that you remove, or drastically reduce, all grains from your diet. I didn’t say “all carbohydrates,” just grains. Your nutrition during this time will consist of lean protein, good fats and plenty of fruit, beans and vegetables. Your nutrition during your runs will change too. More about that later. Eating too many refined carbohydrates or eating a large amount of carbohydrates at one time leads to an increase in usage of carbohydrates for energy. This may be fine if you are already a “lean-machine,” but not if you are trying to get there. Processed or refined carbohydrates (and even whole grains somewhat) cause an insulin response or spike. As insulin increases, fat break.down and oxidation (burning) significantly decreases and eventually “turns off” while this same insulin increase turns up carbohydrate oxidation. This causes us to seek out more carbohydrates and suddenly our diet becomes unbalanced as we become “carb-driven.”
According to Seebohar, “Controlling blood sugar through proper food selection is the key nutrition take-home message. Research proves that eating lean protein and fiber (fruits and vegetables) together has a blood sugar-stabilizing effect as well as being very successful in weight loss strategies.”
Remember, this is not a low-carbohydrate diet; it is a balanced diet. This means your meals will look different from the usual bagels, oatmeal and pasta. Breakfast might be black beans, spinach and eggs (or egg whites), with some feta cheese or salsa on top. It might be yogurt with lots of berries and nuts added in. Lunch and/or dinner could be a huge salad with steak, salmon or tofu on top. Or maybe a lean piece of meat with lots of vegetables and some fruit, along with a small bit of cheese for dessert.
If you cannot go cold turkey on grains, then add a small bit of quinoa or brown rice to your dinner. Snacks can be cut-up veggies with a yogurt-based dip. Try soup, chili, stew, lettuce wraps – be creative!
What about during your workout? If we can’t use refined carbohydrates -sports drinks, gels, bars and pretty much everything we normally eat – what can we consume? The answer is: water and electrolytes.
Yikes! What about that “one gram of carbohydrate per minute, 240 calories an hour”? Will I bonk? Will I die? No. You will lose fat. Your fat. Why? Because you are not training at a high intensity, remember? You are not going through your carbohydrate stores; you are burning fat by staying under your crossover point.
The only reason you would bonk is if you are going too fast, or you completely deplete your fat stores, with the latter being quite unlikely. If you are running over two hours or so, you can add some non-grain-based carbohydrate such as fresh or dried fruit, fruit-nut bars such as Lara bars, or nut butters.
Once you are finished with your run, should you hurry to make that “30-minute window” for refueling? Not necessary. What? You did not deplete your carbohydrate stores…you only made a dent in your fat stores. So rehydrate and have a balanced snack or meal.
Where To Get Tested And Why Be Tested
Is it possible to predict an athlete’s metabolic crossover point without a formal lab metabolic test? It may be possible, but not advisable if you can possibly afford to have it professionally measured. Phil Maffetone uses his “180 Formula.” He subtracts an athlete’s chronological age from 180 and then adjusts it according the athlete’s current fitness and health by using four categories that add zero to 10 beats.
This may be close, but it probably won’t give you your precise heart rate when you make that switch from burning more carbohydrates than fat nor will it tell you your calorie expenditure.
Fortunately, from one simple sub-maximal metabolic test, you can find out how many calories you are burning at different intensities (paces), how many of those calories are coming from fat, and how many from carbohydrates. You will have a visual as to where you need to keep your pace for fat burning. In addition to being more metabolically efficient while running, there are other positive benefits from “becoming ME,” decreasing your body fat, lowering your triglyceride level, controlling insulin levels and bettering your blood lipid profile among them.
The actual test consists of using a metabolic cart and usually a treadmill, but a bicycle can also be used. After fasting for about four hours, and after a thorough warmup, you will be fitted with a mouthpiece, noseclip and headgear to capture your breathing. The test itself may take between 30-60 minutes but is not a maximal test.
You will almost certainly start out walking and every five minutes the speed of the treadmill will be increased (by about 30 seconds per mile) until you have reached your crossover point, and then a bit longer to make sure.
There is a list of Metabolic Testing Centers in the back of Bob Seebohar’s book, Metabolic Efficiency Training. You can do an internet search to find a testing center in your area, and many gyms are also beginning to have this equipment. Just be sure the person administering the test under.stands the protocol to be used. A very cost-effective way to be tested is to go to a college or university that has an Exercise Physiology Department. Graduate students are always looking for guinea pigs…I mean…runners, for research projects.
If you change your diet – the 70-percent effect and if you train at a low intensity (maybe lower than you need to, just to make sure you are not above your crossover point) – the 30-percent effect you will get some results. But to maximize leaning-down in the shortest time frame, get the test.
Metabolic efficiency training can help you stabilize your blood sugars, give you steady energy, lose body fat and allow you to run faster at a lower heart rate. All great results, so think about incorporating ME training into your base training. All you really need to start your ME training once you get the test, is your running shoes, a heart rate monitor and your body fat.
The chart below, from Seebohar’s book, Metabolic Efficiency Training, shows the results of an athlete’s metabolic efficiency sub-maximal test with each line representing a five-minute stage increase with the associated heart rate, calories expended per hour and the amount of fat and carbohydrates of those calories. Looking at the last column, you can see this athlete’s optimal fat-burning intensities were between a 9:32 and 11:46 pace, or a heart rate of 143-165. The lower heart rate and pace would give this runner the most “bang for the buck” – burning the most fat while preserving carbohydrate stores.
|Pace||Heart Rate||Calories per hour/minute||CHO (grams/ calories)||Fat (grams/ calories)|
References And Recommended Readings
Achten, J., Jeukendrup, AE. Optimizing fat oxidation through exercise and diet. Nutrition, 20(716-27). 2004.
Bailey, C. The New Fit or Fat, Mariner Books, Revised Edition 1991.
Coyle, EF, Jeudendrup, AE, Oseto, MC, Hodgkinson, BJ and Zderic, TW. Low-fat diet alters intramuscular substrates and reduces lipolysis and fat oxidation during exercise. Am J Physio Endocrinol Metab 280:E147, 2005.
Flemming, T. Endurance Performance Training Center, Mill Valley, CA, enduranceptc.com/ services/elab
Maffetone, P. The Big Book of Endurance Train.ing and Racing. Skyhorse Publishing Inc., 2010. Schulman, D. Fuel on Fat For the Long Run.
Marathon and Beyond. Sept/Oct. 2002. Seebohar, B. Metabolic Efficiency Training:
Teaching the Body to Burn More Fat. Self-published. Fuel4mance, LLC. 2009. Seebohar, B. Nutrition Periodization for Athletes: Taking Traditional Sports Nutrition to the Next Level (2nd ed.). Boulder, CO. Bull Publishing. 2011.
I’m new here and may be looking at the crossover figure incorrectly, can someone help? It appears to say that at rest 100% of energy needs are met by burning fat for fuel. That cannot be correct. What am I missing….
It is a correct statement, although it doesn’t sound so. At rest, the body does, in fact, burn its largest percentage of calories via fat, but you have to remember that’s a percentage. So you might burn 50% or more of your calories via fat, but it’s 50% of almost nothing.
I dont entirely with this notion that using a greater percentage of fat is beneficial to performance. While the our bodies can be trained to burn more fat, thus sparing muscle glycogen, it comes at a price since burning fat requires more oxygen. So, for any submaximal pace there would be an increase in heart rate until threshold is reached, in which case it’s not going to matter because the working muscles will use almost exclusively glucose for fuel.
Hey Sonny… Thanks so much for this article. When looking for a testing center you mention “Just be sure the person administering the test under.stands the protocol to be used” but I am not clear what I should ask for when I contact one of these centers. Any help?
I just read this article today, and have a question. My understanding is that quinoa is a seed not a grain. So is it okay to be consuming more than the “small bit” you recommended?
“ME training lets your body use fats and carbohydrates more efficiently. It manipulates cellular processes through aerobic training by increasing the size and number of mitochondria in your cells.”
There is very little to support what Seebohar is selling. Endurance training in general is ME training. The idea that you’ll push that cross-over to the right by doing more low intensity training after you’ve already been training a year or more is nonsense. In fact the research is pretty clear; if you want more mitochondria, interval training does it best.
You can, however, very quickly alter your fat burning quickly. One is to spend a few days eating more fat and less carbs; as little as one high fat meal can do that, as shown by Noakes more than a decade ago. Another way is to exercise longer. A short duration test performed after say an hour of easy to hard training will show you a very different result than that same test performed from a resting state.
FYI: Most good exercise physiology labs at a college or university can do this testing, though you may find many questioning the value like I do.
I agree with ESP PODCAST. Several studies have shown no performance benefit to MET as described by Seebohar.
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