Facts on Carbs for Active People
and Periodization of Nutrition
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
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
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
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
Periodization of Nutrition
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
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
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 intake 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
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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