Eating carbs/how fast are they stored?
So most of the carbs are stored as glycogen in the muscles (right?). Lets say i have zero carbs/glycogen/fructose whatever in my system and i start eating carbs. How long it takes for the body to make them ready to use?
Even though i asked that question, im never in that situation because i fuel after workouts so obviously im not really “empty”, but just asking…
The same applies for during and post-workout: our bodies can absorb/metabolise about 60-90g/h. Limiting step is the transfer from the intestine to the blood stream. Hence, it can’t go faster then this.
Transfer from the blood system to the muscle is faster in the first hours after a workout and declines gradually.
If you do not have a second workout scheduled for the same day it does not really matter. Whatever and whenever you eat does not matter, as long as muscles have some storage capacity free carbs go in there.
nice readable overview of glycogen utilitsation and replenishment. What I like about it in particular is that the reviewed data is on trained subjects only. Not active or untrained like in many other studies.
Macklin et al.2019.A Meta-Analytical Review of Muscle Glycogen Replenishment.pdf (811.2 KB)
Does how insulin sensitive you are have a bearing on it as well. i.e. if you are relatively insensitive to insulin a greater proportion of the carbs would be converted to fat rather than to replenish glycogen stores?
Dangerous bro science terrain
First of all: one of the key adaptions of endurance training (at already very low doses) is becoming more insulin sensitive. The body makes sure that you have the proper infrastructure for repleneshing your stores. So being insulin insensitive is not really such a big issue for healthy, active people. But I know, we live in a world where everyone is gluten and lactose intolerant. So it’s only a small step to being insulin insenstive as well … I’m talking now about healthy, active people. I don’t want to offend the (few) people with a real condition.
It is generally advised these days to schedule your carb intake according to your activity level. Periodized carb intake (not talking low-glycogen training now).
When you exercise muscles get glucose without the help of insulin (GLUT4). This mechanism is still active post-workout. Therefore, the recommendation to eat carbs around your workouts. Furthermore (if I remember correctly), the body is more insulin sensitive post-workout. Add this to the already gained chronic sensitivity due to endurance training. This all adds up and makes sure glucose gets into your muscle to replenish glycogen.
Of course, once your stores are full all the sensitivity does not help further and carbs go (potentially) to fat. That’s why only moderate carb amounts are suggested for easy training days. Not much to replenish.
This is probably an oversimplification but I believe this is one of the models currently discussed in physiology.
Thanks. I’m getting very confused with all the information that’s available nowadays. It may be an oversimplification but sometimes that is needed to make it understandable to the likes of myself.
My physiology texts in college all said it takes about 3 hours for CHO to go from the gut to be stored as muscle glycogen, or to end up in the liver. Not used after 5 hours, converted to body fat.
Hence the rationale for the pre-competition meal to be 3-5 hours before the event. Or, ideally you eat your pre-training meal 3 hours before your workout.
I don’t split hairs about this CHO or that CHO. Eat minimally processed food* and avoid the simple sugars unless it’s right after training.
Don’t know if that’s bro science – I’d prefer “uncomplicatedly sensible.”
- I do eat a couple of Clif bars every day, but apart from that its oatmeal, sandwiches, veggies and fruits and eggs and crap.
Wow, that’s slower than I would have expected. Don’t gels act quicker than this?
gel, syrup, honey – all that is going to act quickly.
the 3-5 hour window assumes you’re eating moderate-glycemic stuff that you have to chew – which, really, is how you should be eating anyway. sucking down a lot of simple sugar is a pretty crap way to fuel yourself. Colby Pearce had some thoughts on this in the last VeloNews podcast.
When I started in the early 80s, it was still the era of bananas, ham sandwiches, and flaky pastry tarts in the feed bag or jersey pocket. Then things swung to energy bars and squeezy packs (ick).
Hopefully we are swinging back to a middle ground.