CHO uptake and limits, seriously?

stormer94 said:

It seems to be common lately to read that maximum CHO uptake for most fit humans is around 1gr/kg of body weight per hour. And the gastric absorption, or emptying rates of fluids into the system, is between 17-28 fl oz per hour.

Here's the question. Based on those numbers and a good 5-6 hour ride for myself, I'm gonna lose like 6-10 pounds on a ride (nice, hot, sunny day). Is it seriously okay to do that???????? I've been trying to weigh the same, +- a pound after a long ride.

If I'm buring 700-900 calories per hour for 5 hours, that's 4200-5400 calories out the window. and I can only uptake about 240-280 calories an hour through calorie oxidation and gastric absorption, I'm in a serious problem.

I can't eat enough in a day, based on hours of being awake, and say 250 calories an hour, to get those back. Even if I choke down 500 calories every 2 hours, that's short 200 calories per hour, and you're eating like a homeless junkie, ALL DAY!

So how is it recommended to survive long rides? I had been drinking about 40-48 ounces an hour on long hot rides, I'm reading 17-28 is all that the system can empty. Is it possible on last Saturdays 4.5 hour ride I over drank by 100 ounces? how can that be? I came home 2 pounds light. Add to that, those 48 ounces are cytomax and 300 calories per hour, and toss in 1.5 power bars per hour, that's 700+ calories per hour I've been trying to take in. Usually pretty successfully, but I still come back lightweight after a long ride. Now I'm reading I should eat and hydrate even less, by like HALF :eek:

I'm having trouble wrapping around this, Should I be withered and 10 pounds lighter after a long ride??? Doesn't seem right to me.

Briefly, as there is a lot of info on this in other threads and it would be easy to write a thesis in response to this.

You only need to replace carbohydrate (CHO), as fat is essentially unlimited in its metabolic availability, and protein/amino acids are not normally used as a fuel source provided sufficient CHO is available. As such, it is better to count CHO consumption rather than raw calories. Since you will not oxidise exclusively CHO (also fat), you do not need to replace all your calories burnt while on the bike. Your main concern is to maximise your body's ability to uptake and process CHO. You do this by consuming the right amount and type of fluid, CHO and electrolytes.

Oxidation rates of up to 1.75g/minute of exogenous CHO have been reported from consumption of mixed CHO solutions (glucose/maltodextrin + fructose). Some studies suggest that you need to eat more than you will oxidise, perhaps 2/g mixed CHO/minute, 120g an hour, in extreme conditions.

Body weight loss of 2-3kg is commonly reported in sustained endurance exercise. While you should try to replace fluids and electrolytes, I don't think it is a major concern as long as it is within those limits.