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“While low-carb diets have their merits for a select population, a nutrition program higher in carbohydrates is much more appropriate for you as an athlete.” --Chris Carmichael’s Food for Fitness (Putnam, 2004)
Carol and I are fans and admirers of Lance Armstrong as an athlete and a cancer survivor. I greatly enjoyed his best-selling books, It’s Not About the Bike and Every Second Counts. Needless to say, we followed every stage of his record sixth victory in the Tour de France. In the course of watching Lance’s commanding performance on OLN, I learned that Chris Carmichael, his longtime personal coach, has just come out with a book on nutrition. Food for Fitness, written with Jim Rutberg and Kathy Zawadzki, is unique in that it’s not about losing weight or preventing some life-threatening disease. To quote an editorial review from Publishers Weekly, it’s written for “a minority group living in a society struggling to cope with serious health issues,” namely athletes and active people. An excellent book, it explains in straightforward, easy-to-understand language the how and why of eating to fuel an active, performance oriented lifestyle. Well researched, it covers what athletes and active people need to know.
Rather than a complete review, I want to discuss several topics I found especially interesting: intensity and fat burn, low-carb diets, and periodization of nutrition.
Intensity and Fat Burn
Having written about the so-called fat burn zone (article 10 above and Challenge Yourself), I was eager to read Carmichael’s take on the topic. “It’s important to realize that you burn carbohydrates, protein, and fat simultaneously whenever you exercise, regardless of the intensity,” Carmichael writes. “There’s no such thing as an exercise that only burns fat.” The proportions do change with the intensity of the exercise, however.
Three primary energy systems are involved every time you exercise--immediate, aerobic (with oxygen) and anaerobic (without)--and the percentage of energy supplied by each system shifts as the intensity of the workout changes. Your diet and fitness level also influence the energy source.
The immediate energy system isn’t a major energy supplier, because it can only supply energy for about 8 to 15 seconds. The aerobic and anaerobic systems are the main producers.
At low intensity, 20 to 25 percent of maximum effort, most of the energy is supplied by fat, from food and mobilization of fat stores. “It’s important to note, however, that in order for your muscles to burn fat in the aerobic system, carbohydrate has to be present,” Carmichael explains. “In conditions where your body is depleted of carbohydrates, the rate at which you burn fat decreases, and your capacity for high-intensity disappears.”
At 40 to 50 percent of maximum effort, you burn roughly 50/50 fat and carbs, almost all through the aerobic system. “The percentage of energy derived from carbohydrate increases as intensity increases, in part because you need energy more quickly than it can be liberated from fat,” Carmichael continues. “If it were possible to only burn fat for energy, you would be limited to exercise under 60 percent of your maximum effort.”
The shift to burning more carbs than fat occurs when the anaerobic system comes into play. “Fat can only be oxidized through aerobic metabolism, but carbohydrate is burned aerobically and anaerobically,” writes Carmichael. When the aerobic system can no longer keep up with increasing intensity, the anaerobic system kicks in and fat-burn percentage goes down. The relative contribution from carbs, of course, increases with the intensity.
From 50 to 85 percent intensity, the contribution from fat continues going down. The aerobic system is still providing a large portion of the energy, however. Above 85 percent, the proportion of energy from fat decreases even more.
Hmmm. Sounds like the fat-burn-zone crowd may be onto something. But wait.
“You’re still burning a lot of fat,” Carmichael assures readers. “You may derive the highest percentage of your energy from fat when you exercise at low aerobic intensities, but when you increase your intensity, you burn more total calories and more fat.”
Finally, Carmichael adds another fundamental point: “Low intensity exercise is also less likely to induce enough of a training load to improve fitness.” To become more fit, you need overload. Greater fitness enables you to do more work aerobically and anaerobically—and burn more fat.
As you’ve probably figured out by now, the energy systems are also central to the low-carb issue.
Chris Carmichael: “Low-carbohydrate diets were devised to help overweight and obese people lose body mass in order to improve health. They were not devised with the intention of improving performance.” To the contrary, such diets inhibit athletic performance.
As noted above, high intensity exercise is impossible without adequate carbohydrates; fat simply cannot supply energy fast enough to support maximum performance. That doesn’t mean low-carb diets have no merit, however. “Considering the fact that low-intensity exercise can be beneficial for primarily sedentary people and that low-intensity exercise may be sustainable on a low-carb diet,” Carmichael reasons, “sedentary people may benefit from low-carb diets.” That’s not true for active people and athletes, however.
The basic idea of the low-carb diet is that depriving the body of carbohydrates will force it to burn fat. As low-carb dieters know, this is called ketosis. In the absence of carbohydrates, your body transports fatty acids to the liver to be converted to ketone bodies. Ketones provide the brain and central nervous system with the steady supply of energy required for survival. Ketones are also capable of supporting low-intensity aerobic exercise. Carmichael warns, however: “You can’t generate energy anaerobically with ketones, which is one of the reasons athletes on low-carbohydrate diets struggle to sustain even moderate-intensity exercise.”
This explains bonking or hitting the wall, which usually occurs hours into a long workout when blood sugar starts running low. Glucose, blood sugar, is the preferred fuel for your brain and central nervous system. “Bonking is your body’s way of forcing you to stop exercising while there is still enough glucose in your blood to maintain normal bodily function,” Carmichael writes. “Athletes eating low-carbohydrate diets bonk earlier than normal because they start workouts glycogen-depleted. As a result, they have far less fuel than needed to supply energy for muscles and the central nervous system.”
There’s more, but this should be enough to provide substantial food for thought.
Most of our visitors are familiar with the concept of periodization as applied to training; see article 8 above and Ripped 3. Generally speaking, in strength training, volume starts high and intensity low, and reverses over several periods, with volume low and intensity high at the end of the training cycle. Chris Carmichael defines the concept more broadly: "Periodization is the process of breaking the year into segments so you progress through a planned series of steps." He breaks the training year into four big segments: Foundation, Preparation, Specialization, and Transition periods. The basic idea is the same, however. What's new is that he extends the concept to an athlete's nutrition.
"Different training periods require different fuel mixtures, and when the fuel matches your demands, you reap huge rewards," Carmichael maintains. Calorie consumption, of course, changes as the cycle unfolds. "Beyond the number of calories you're eating, your training also influences the kind of food you eat," Carmichael continues. As we've seen, the amount of carbohydrate you burn increases with intensity. It should come as no surprise that protein and fat requirements change as well.
Carmichael gives recommended ranges for carb, protein, fat and calorie consumption for each of the four periods: Carbohydrate 2.5-3.0 (grams per pound), Protein 0.5-0.6 (g/lb), Calories (for a 165 pound man) 2500-4200. Recommended fat intake is between 12 and 30 percent of total calories, with saturated fat limited to between 6 and 10 percent.
Carmichael admits that his recommendations are not written in stone. "It is nearly impossible to doggedly adhere to fixed macronutrient intakes and percentages," he acknowledges. "It's not practical or necessary, to weigh your food or pre-plan every meal."
Focus on the big picture, the trends, says Carmichael. "For instance, caloric intake increases as training volume and intensity increase," he explains. "While changes in carbohydrate and protein intakes track together, fat intake rises through the Foundation and Preparation periods, and then stays constant or falls during the Specialization Period."
I used the computerized diet analysis from my last trip to the Cooper Clinic (article 128) to see how I track with Carmichael's recommendations. I'm definitely in the ballpark, especially in the carbohydrate department, which Carmichael considers the most important. My carb intake is 2.45 grams per pound, a hair under his recommended range, but probably about right considering that I'm not an endurance athlete. My protein intake is 0.83 grams per pound, a little over, but probably right on for someone who emphasizes weights and aerobics equally. My fat intake was 30%, with only 3% saturated. At 2735, my calorie intakes is at the low end of Carmichael's recommended range. My weight is stable and, again, I'm not an endurance athlete.
I can confirm that it is quite possible to stay in the recommended ranges without counting calories or weighing your food. As those who have my books and videos know, I plan my meals and eat mostly whole or minimally processed foods. I also record my weight and body fat every week, on my Tanita scale. If I'm hungry I eat more, but I make no effort to vary my calorie intake from day to day, or based on where I am in my training cycle. I do fine-tune my diet and training when the mirror and/or Tanita body weight/fat scale tell me I should.
Chris Carmichael's periodized nutrition program makes sense in theory. I'm sure it works for Lance Armstrong. How close you chose to adhere to it is up to you. Your decision should probably be based on your fitness level, your circumstances and your goals.
One thing is certain: Chris Carmichael's Food for Fitness is a book worth reading.
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