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In many ways,
dietary carbohydrate is the one macronutrient that's most
apt to be manipulated during the year by strength athletes.
Protein can be held steady effectively at around one gram
per pound of body mass and research suggests dietary fat
should be kept at about 85-100g daily for many men to maintain
higher testosterone levels.(2, 14)
But as a readily
dispensable and fluctuating fuel, carbohydrate can differ.
Its insulinogenic and muscle (glycogen) expanding properties
make it attractive during mass building phases but there
are also times of the year when fat loss becomes a goal.
(Insulin stimulation is not conducive to fat loss at all.)
Beyond this, there are a number of factors that influence
and hamper dietary carbohydrate "handling".
Some of these
are modifiable (self-induced and environmental) and some
are non-modifiable (genetic and age-related). Let's review
them…
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1. Muscle Soreness
It's not really up
for debate anymore that sore and micro-traumatized muscles (from
eccentric contractions, or "negatives") don't take-up
blood sugar well. They have perturbations in the biochemical insulin
pathways and just don't accumulate glycogen as well as "non-sore"
muscles do.(3, 16, 18) Are you someone who is routinely sore,
nearly from head to toe? I am.
And I wonder if, coupled
with a family history of Type II diabetes, that this makes me
someone who might do better on a 40-50% carbohydrate diet than
the oft-recommended 60-70% carb diets promulgated by many "sports
nutritionists".
I mean, if my sore
and recovering muscles aren't taking-up the resulting blood sugar,
where might it be going? (The liver can only store so much, typically
70-90 grams, so is triacylglycerol [fat] storage the net result?)
Hence, these days I tend to consume breads and pastas as treats
rather than staple foods - and know what? I find myself eating
more vegetables because of it.
2. Middle Age
It has been stated
that the consumption of sugars and fats are associated with the
glucose intolerance seen in mid-life.(13) Indeed, reductions in
"carb handling" such as impaired insulin sensitivity
and beta cell function by middle-age are not unheard of by any
means.
Yet aging isn't a modifiable
risk factor is it? If you don't want to turn 40, tough cookies.
And yet there is hope (beyond avoiding cookies). Many of us are
already aware of it: Both aerobic conditioning and resistance
training strongly compensate for the glucose intolerance seen
during aging (even "middle-aging").(15)
Muscle contractions
can maximally take up blood sugar without insulin's presence ("GLUT-4
translocation" for you nerds), blood flow goes to where it
should (muscle should be receiving 70-80% of ingested carbohydrate),
muscle mass is maintained and central body fat is reduced, and
long term glucose tolerance is improved (except during periods
of eccentric soreness). The take home message? Lift and do your
cardio.
3. Family History
Researchers have documented
that relatives of those with Type II diabetes are themselves poorer
"carbohydrate handlers".(5, 12) This is another one
of those un-modifiable risk factors. (Perhaps you should have
chosen your parents more wisely?)
And so we are left
correcting for a certain genomic propensity towards glucose intolerance
and/or hyper-insulinemia. Fortunately, researchers have also provided
some potential answers. In a famous study by Jenkins and colleagues,
nibbling several small meals, as opposed to "gorging"
on three big ones each day decreased insulin concentrations 28%
(and cortisol 17%, a nice bonus).
This really rolls
with my mantra of daily meals: "Eat it… burn it…
eat it… burn it". Your body runs continuously, not
intermittently, so why not consider feeding it thusly? I think
it's also fascinating that soluble fibers, such as that of oat
bran, slows the movement, digestion and absorption of food - much
to a poor "carb handler's" advantage. We're talking
about decreasing post-meal insulin concentrations 35%, and glucose
levels 50%.(17)
And before you think
that you have no family history - and are thus in no need of smaller
frequent meals or oats - consider this: At least 20% of the population
has metabolic syndrome (a collection of insulin insensitivity
and various cardiovascular risk factors). Plus, 6% of college
students are in a similar boat.(7)
4. Eating Late on Non-exercise Days
The tenets of "Temporal
Nutrition" are based in part on the premise that even healthy
persons' glucose tolerance is not very good at night.(4, 10, 19)
Have you ever heard of the nurse's health study in which nighttime
eaters gained more weight and fat than similarly-eating daytime
counterparts? It's still further support of this temporal concept
in my opinion.
But what to do?
We can't stop the daily clock!
Well, as noted above
under the "Middle-age" heading, exercise is a great
modulator of glucose metabolism- and it helps on those evenings
of the week when we are actually in the gym. But who can - or
would want to - work out seven days per week?
I suggest that, if
you feel a carb reduction (of say 10%) in your daily diet is warranted,
you first consider removing bread and pasta from your "off
day" dinners (perhaps 2-3 nights each week). As I said above,
you may find yourself eating more veg - thus improving overall
diet quality - because of this simple change.
5. Dieting Phases
As a nutritional biochemisty
professor, I see a real trend in many textbooks (check out the
paperback, Biochemistry Primer for Exercise Science by Mike Houston
as a good start) that supports potential problems with chronically
high carbohydrate diets (and their accompanying hyper-insulinemia).
These diets induce gene changes over time that produce lipogenic
("fat building") enzymes in the body.
You see, not long
after learning that insulin is a hormone that "pushes sugar
out of the bloodstream and into tissues", an avid student
learns that it's a storage hormone that is also strongly involved
in triacylglycerol (fat) storage. It simultaneously inhibits the
biochemical "fat breakdown machinery" in cells.
Overall these are good
things, maintaining body weight and keeping us from being diabetic.
Trust me, you don't ant to rapidly and seriously lose huge amounts
of both muscle and fat in the way an uncontrolled Type I diabetic
person does.
Nonetheless, for
the "dieter", reducing carbohydrate can be a primary
tool in reducing body fat. This can be as simple as not drinking
sugary carbs with meals (1), keeping carbs out of the "fat
burning" pre-cardio period (11), switching to higher fiber
foods such as oat bran over oatmeal, or removing bread and pasta
from meals a few nights each week.
Since protein needs
will be maintained or increased as one diets, and going to a super
low-fat diet can have the aforementioned hormonal consequences,
this is a sane approach to "nutritional periodization".
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Hopefully this little
exploration of the scientific literature and the practical aspects
of carbohydrates was helpful. Of course, for those enduring frequent
and long bouts of training, keeping carbohydrate intake up is
important to fight fatigue, overtraining, muscle "flatness"
and other reasons. But for those readers who experience a collection
of this article's five cautionary factors, the potential solutions
herein may be just the ticket.
For references,
see below...
