Question on calorie replacement?

Walrus said:

[font=Helv]I found this article and thought it looked like a reasonable method of calculating calorie replacement, taking into account ride time, weight, speed & ascent. However, I don't quite understand one part of the formula, and I was hoping to get some opinions on it.

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The part I don't understand is steps 5 & 6. Why, after calculating the calorie needs, you then aim to replace between 30% and 50%? Does this mean that my body is burning x calories, but I only want to replace between 30-50% of that? If so, why? If not, what am I missing? The article talks about people overestimating calorie replacement, but I thought the idea was to replace what you use?

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There is an upper limit how much carbs can be absorbed per hour, in the litterature are values like maximum of 50 - 70 grams of carbs per hour given. I assume the percentages are calculated for not to exceed those levels. And as a lot of energy is coming from the fat stores anyway, there isn't need for 100% replacements either.

Walrus said:

[font=Helv] Does this mean that my body is burning x calories, but I only want to replace between 30-50% of that? If so, why? [/font]

In addition to Sidewind's comment about absorbtion rates there's also the question of carbs, fat and protien breakdown. If you're trying to maintain weight then replacing all the calories burned in your ride plus all calories burned during the rest of the day(your basal metabolism plus any other activities) over a 24 hour period is in order.

A lot of folks use these calories burned during exercise tables to aid weight loss. If you're trying to drop pounds but still want to support an exercise program you have to replenish your glycogen but don't want to replace all the calories you burned. Weight loss requires you to be hypocaloric but if you don't replenish most to all of the glycogen you consume you'll deplete your glycogen reserves over consecutive days and run out of steam for training purposes.

My take on the recommendation to replace 30-50% of the calories burned is that it attempts to replace the glycogen but not the fat. That's because you burn different ratios of fat to carbs depending on workload with higher fat ratios at low workout intensities. So at an easy L2 endurance pace you'd be primarily burning fat and you'd want to replace a lower percentage of your total calories burned say 30%. If you're working in higher levels say L4 work at your max 1 hour pace you'll be burning more glycogen and need to replace a higher percentage of your overall calories burned with carbs.

This assumes you're trying to stay hypocaloric but still replenish your glycogen stores to sustain future training efforts. If you're happy with your weight and actually trying to maintain or even build weight then you'd want to estimate your basal metabolic rate, the sum of all other activities add these to your training caloric load and replace the whole shebang each day.

Good luck,
Dave