I was having a discussion with a guy who was gonna be doing an ironman. I was telling him there’s a limit to how much you should eat, considering you can only absorb so much food while you’re out exercising. I said it was probably between 150 - 200 calories (i.e. kCal) an hour, but he seemed skeptical, which made me skeptical too.
So I was wondering: are there any studies out there that measure how much food can be:
Digested
Absorbed and converted into usable energy
On a related note, how can this be subdivided into:
Sugars (simple carbs)
a. Between different types of sugars, e.g. glucose, sucrose, di / oligo saccharides
Starchy foods (complex carbs)
Protein
Amino acids (digested protein)
Fats
Would such combinations increase the amount of energy replenished? E.g. would sugar + protein (a la accelerade, and other protein + sugar drinks) allow you to absorb more calorific energy per hour?
And how would this be affected by what physiological state you’re in? i.e. exercising (in different zones?), bumming around, sleeping…
Comprehensive question, hoping to obtain comprehensive answer from the slowtwitch experts out there…
[That said, you don’t want to go through your glycogen stores early in the race—you’ll need them later. This is because the critical factor is not how much you ingest during the race. Yes, this is important, but more important are your burn rate and your absorption rate. Your burn rate is going to be higher if you go harder. And remember, you’re burning about the same amount of fat riding a slower pace as you are riding a faster one, and all the additional fuel required to go faster is much-needed carbohydrate.
This is important for two reasons. First, when you run out of carbohydrate, as we discussed, you really run out of two fuel sources: carbohydrate and fat. And when you’re riding harder you’re going through carbohydrates very, very quickly. ]
Cut and pasted a little segment from it. Highlighted a section which is very pertinent.
My thinking is even someone very well trained could burn off their glycogen stores pretty fast if they go really hard. That has been an experience I found,…holding back is tricky when you feel so strong…or at least it is a mistake which is easy enough to do.
According to two different nutrition books it can even go as low as 100 calories per hour depending on the heat etc. But they mention the same thing an average athlete can burn about 300 calories per hour but body can absorb anout 150 to 200. Most people make the mistake here they aim for 300 and the problems start…
According to two different nutrition books it can even go as low as 100 calories per hour depending on the heat etc. But they mention the same thing an average athlete can burn about 300 calories per hour but body can absorb anout 150 to 200. Most people make the mistake here they aim for 300 and the problems start…
I think the average athlete can burn more than 300 calories per hour.
The higher your exhertion rate, the lower your absorption rate
The higher the stress level to your gut (heat, mental stress, physical stress), the lower the absoption rate
The higher the osmolality (closest to 300 best), the lower the absrption rate.
So, how many cals absrbed per hour depends on your exhertion, stress level and what you are eating/drinking
Of course, clinically, there is a lot more happeneing here than this. getting too deep into the clinical end of it gets confusing.
Trial and error is the way to go. The average person can take in 150-300 calories per hour during IM intensity, but you will not know until you practice it.
Pay attention to where your calories are coming from. I like to have my athletes shoot for about 7 carbs to 1 protein. Don’t worry about the fat so much, if you are eating bars the fat you need will be in them. I just wouldn’t look to add any extra fat.
Simple sugars are not the best idea until the last 1 -5 miles of the race. Think of simple sugars as rocket fuel, burns fat, gives great energy, but burns up quickly.
Amino Acids don’t do much if anything if taken during a race, this is because of their absorption rate in supplement form. It’s VERY poor.
According to two different nutrition books it can even go as low as 100 calories per hour depending on the heat etc. But they mention the same thing an average athlete can burn about 300 calories per hour but body can absorb anout 150 to 200. Most people make the mistake here they aim for 300 and the problems start…
I think the average athlete can burn more than 300 calories per hour.
It all depends on the level of the effort and the size. it could be much more than 300. But no matter how much you burn the consumption is a lot lower than it.