Do regular exercisers really benefit by eating a load of bread and pasta?

*Do regular exercisers really benefit by eating a load of bread and pasta?*

Posted By _Dr John Briffa_ On November 20, 2009 @ 5:57 pm In _Exercise
and Activity_, _Low-Carbohydrate/Carbohydrate Restriction_ |

I have been doing some lecturing this week, and part of the information
I imparted concerned the potential advantages of eating a diet
relatively low in carbohydrate. It's not uncommon for individuals to ask
about the potential effect of low-carb eating on sporting performance.
This question is usually rooted in the notion that those engaging in
regular sporting activity or exercise need to maintain their stores of a
starch-like substance called glycogen (found mainly in the muscles and
liver), which provides relatively ready fuel during exercise. Glycogen
is a carbohydrate, and so exercisers are often encouraged to 'carb-load'
in an effort to fill up the glycogen stores so that plenty of ready
energy will be available during exercise. People downing plates of pasta
the day before a marathon is borne out of this theory.

However, is carb-loading really necessary for most mere mortals? Let's
work through some figures. A 30-minute jog will burn about 250 calories
in addition to those that would be burned sat still. A significant
proportion of the fuel for this exercise will come from fat. Let's
imagine, that during the jog, 150 of the calories come from carb. Each
gram of carb contains 4 calories, so in theory to replenish the glycogen
lost during exercise is going to need the consumption of about 40 grams
of carb. That's about the same amount of carb found in a couple of apples.

In other words, for most individuals engaged in recreational exercise
that doesn't go on for hours, glycogen depletion is unlikely to be an
issue unless carb consumption is cut to very low levels.

For endurance sports, low-carb eating is potentially more of an issue.
If you're training for a marathon, for instance, and racking up 50 miles
or more a week, then glycogen depletion is a real risk. However, one
thing that needs to be borne in mind is that when carbohydrate is
restricted, the body automatically turns to other fuels (principally
fat) to make up the difference. This adaptation can take time, so
adopting a low-carb diet is not the thing to do a week before a
marathon, particularly if your goal in not just to 'get round' but crack
your personal best.

At lower intensities of exercise, however, adopting a low-carbohydrate
diet does not appear to be an impediment to activity. A major review on
the subject concluded that "…endurance performance can be sustained
despite the virtual exclusion of carbohydrate from the human diet." [1].

There is no doubt in my mind that the very physically active can
tolerate more carb in their diet than those who are not. If this applies
to you, then aim to get your additional carbohydrate into the system
within an hour or so after a sporting event or training session (this
help replenishment of glycogen in the muscles for future use).

If you do feel the need to do this, I would counsel against using bread,
pasta and white rice as your carbohydrate sources. Not only are these
foods generally disruptive to blood sugar, they also offer precious
little from a nutritional perspective. Generally slower sugar-releasing
and more nutritious forms of carb include fruit, vegetables and legumes
(beans and lentils).

*References:*

1. Phinney SD. Ketogenic diets and physical performance. Nutr Metab
(Lond). 2004;1:2

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