Official Sprocket Rockets Training Thread

[J. Barron DeJong]

My grade-school understanding:

Table sugar is sucrose, which is a 1:1 glucose:fructose disaccharide. Glucose uptake maxes out around 50-60 g/hr, IIRC. Fructose uptake happens via a separate metabolic pathway, but for a long time it was thought that fructose utilization during exercise was low so the focus was placed on glucose sources, such as dextrose and maltodextrin. When people started actually studying fructose utilization they found that it was actually much higher than anticipated, so the "ideal" G:F ratio has climbed from 3:1, to 2:1, and now 1:1 appears to be ideal, or at least below the tolerable upper limit for fructose intake.

Thanks. Couldn’t remember which sugars they were, and recalled hearing those higher ratios before.

[XtrPickels]

My grade-school understanding:

Table sugar is sucrose, which is a 1:1 glucose:fructose disaccharide. Glucose uptake maxes out around 50-60 g/hr, IIRC. Fructose uptake happens via a separate metabolic pathway, but for a long time it was thought that fructose utilization during exercise was low so the focus was placed on glucose sources, such as dextrose and maltodextrin. When people started actually studying fructose utilization they found that it was actually much higher than anticipated, so the "ideal" G:F ratio has climbed from 3:1, to 2:1, and now 1:1 appears to be ideal, or at least below the tolerable upper limit for fructose intake.

Pretty spot on.
Glucose is primarily transported out of the small intestine by SGLT1, and Fructose is transported by GLUT5.
All of the current conversation is centered around sugar molecule transport out of the gut. But, there are multiple steps in this process.

1. The sugar needs to be ingested into the stomach
2. It needs to leave the stomach (Previous research on "Tonicity" / concentration)
3. It needs to travel the gut (Previous research on "Tonicity" / concentration)
4. It needs to be removed from the gut and put into the blood-stream (This is the current conversation / new research)
5. It needs to be utilized for energy (metabolized) (This is the current conversation / new research)

What we know from the past is that too high of sugar concentration makes for slower gastric emptying and it can also cause issues as it moves through the gut as it needs to pull water in to lower the concentration. So, when we discuss these high concentrations, there is a risk of GI distress if an increase in fluid volume does not occur as well. For example if I'd doing 120g/hr, it works best with 750+ml per hour of fluid. I can do it in 500ml/hr, but I do notice slight stomach discomfort.

Additionally, the body is not innately able to transport these high sugar loads. It has to develop and improve the function of the transporters, so easing into it is preferable.

Fructose does still have some potential for GI distress and it's processed different via the liver, so Glucose is the safer bet.
Additionally, Fructose metabolism is relatively low UNTIL glucose transport is maxed out, then the body seems to (magically) oxidize more fructose.

Therefore, I like to keep my glucose toward the high end of absorption, so I vary ratios depending on carbohydrate intake, but more research needs to occur to know if this is strictly necessary.

Up to 60g/hr I do straight glucose / maltodextrin
from 60 to 90g/hr I shoot for a 2:1 Glucose:Fructose Ratio (60grams glucose + 30grams Fructose)
Above 90g/hr I shoot for 1:1. (60g glucose +60g fructose)

The research is mostly centered around 1:0.8, but this is likely so that companies like SIS can have a "unique" (ie not "table sugar") product to sell. However, it appears that functionally the 1:1 in sucrose is fine.

[Dantheman]

Glucose transport maxes out at pretty low intensities, right?

[XtrPickels]

Glucose transport maxes out at pretty low intensities, right?

Gastric emptying increases from rest through low intensity exercise. Once you approach threshold intensity, gastric emptying rates decrease.

I'm not aware of specific effect of intensity on carbohydrate transport across the gut lining, beyond an increase in transporter expression at low-intensities. On one hand it would make sense to increase as oxidation rates increase, however, with increasing intensity there is less blood flow to the gut and one would assume a decrease in transport. It's likely however that this is limited by the changing rates in gastric emptying and that the only way to study it would be to shunt carbohydrate past the stomach and directly into the small intestine which is both unpleasant and not representative of real-world conditions.

A quick google scholar search does not return anything definitive.

As a side note, gastric emptying is tied to fluid volume ingestion and rates increase up to a 600ml fluid bolus (volume at once). Above that rates level / decrease. So, if you want to move fluid quickly, it's best to drink more volume less frequently.

https://sci-hub.wf/10.1152/jappl.1974.37.5.679

This is another paper from Saltin whom suggests that transport rates do not change in severe intensity exercise. However, this paper also states that gastric emptying rates do not change which contradicts the findings of the above linked paper which he also authored.... so take it with a grain of salt.

https://sci-hub.wf/10.1152/jappl.1967.23.3.331

[XtrPickels]

This GSSI paper by Asker Jeukendrup does a great job of explaining theory and citing past work. However, Asker is in the camp of maximizing at 90g/hr and hasn't embraced up to 120g/hr.

https://www.gssiweb.org/sports-scien...their-benefits

[Dantheman]

Interesting. So, since you said fructose utilization is low until glucose transport is maxed out, what are the intensity levels for your <60 g/hr, 60-90 g/hr, and >90 g/hr thresholds?

[dcpnz]

Are you all literally just putting table sugar in water?
Nothing else, no flavor, no electrolytes ?

Just tried to down a glass full and that really ain’t gonna work for me without something else in there to make it more palatable

[climberevan]

I've posted my recipe before, but here you go:

600g table sugar (slow white death)
10g salt (maybe a bit more if you're a very salty sweater)
1 packet unsweetened Kool Aid Lemon

It's sweet, obviously, but the lemon mellows it out a bit. You could do 1.5 packs if you like the sour.

80-100g of this per 750ml bottle does a body good. As noted you need to build up to this--start with 60g.

[fool]

Following DTM’s recipe I added true lemon to mine, and I’m also going to add citric acid for the next batch. Honestly pretty tasty.


Sent from my iPhone using TGR Forums

[XtrPickels]

Are you all literally just putting table sugar in water?
Nothing else, no flavor, no electrolytes ?

Just tried to down a glass full and that really ain’t gonna work for me without something else in there to make it more palatable

I use typically Sodium Citrate instead of table salt. No flavoring for me.

[XtrPickels]

Interesting. So, since you said fructose utilization is low until glucose transport is maxed out, what are the intensity levels for your <60 g/hr, 60-90 g/hr, and >90 g/hr thresholds?

Personally, no restrictions, but I also only fuel this high for multiple hour XC rides, so the intensity it typically held to base / tempo with excursions to threshold and above as needed.
If I'm out mountain biking with friends then I'll do 30 to 60g/hr plus more regular food as we're typically more stop and go.

[fool]

The weight gain when you have some carbs (especially when you’re already restricting carbs) is literally 80% water, the rest is glycogen stored in your muscles. Keep fat intake low when you're in a high carb consumption phase and there won't be much to store as body fat.

Can you expand on this? I'm interested in how to consume carbs vs. protein vs. fat in general, and relative to different phases (and what they are - high-carb, etc.). Years ago I was more inclined to high-fat (OFM) but have been more carb friendly for last few years. That being said, I sometimes will consider 100 cals of almonds better than 100 cals of oatmeal, though I think that's more muscle memory than anything.

GCN has a video with Skye's head of nutrition from five years ago emphasizing protein (in addition to carbs). And I also thought Dylan Johnson's video on losing weight was good too (three years old).

[bean]

Can you expand on this? I'm interested in how to consume carbs vs. protein vs. fat in general, and relative to different phases (and what they are - high-carb, etc.). Years ago I was more inclined to high-fat (OFM) but have been more carb friendly for last few years. That being said, I sometimes will consider 100 cals of almonds better than 100 cals of oatmeal, though I think that's more muscle memory than anything.

Glycogen is stored with 3-4 parts of water per part of glycogen. I don't understand what causes the range, XtrPickels probably does.

The vast majority of body fat is stored dietary fat. For de novo lipogenesis (creation of new fat from carbs) to take place you have to go HAM on the carb intake - like in excess of 400g/day while being completely sedentary. The rapid swings in weight from carb restriction/consumption are changes in water weight. So if you want to get super lean, look to what bodybuilders do on a cut - high protein, moderate carb, low fat, along with good amounts of base-level cardio. Low fat intake means there's not much that can be stored. And the low-intensity cardio primarily burns fat.

But all that is assuming you're trying to cut, or you're in a demanding training block and need to fuel it without putting on fat. For most people walking around most of the time, some degree of carb restriction can be helpful. Low-carb diets can help with regulating hunger and make it easier to maintain (if you're already around where you want to be) or lose (if you need to) fat. When I'm training hard I'll have oatmeal almost every day, but when I'm on vacation and at a low level of activity I'll skip some of the simple carbs and load up on more eggs and meat at breakfast, for example.

Unfortunately there's not a lot of great research on carb-restriction. There's some that's worthwhile but most of it is confounded by problems with the test subjects, durations, studied outcomes, and often advocacy (either pro- or anti-) on the part of the researchers. Nutrition science is really, really hard to do because subject adherence is poor, it's expensive to provide food, if food isn't provided the food surveys are unreliable, finding the right subjects is nearly impossible, the list goes on.

I have a relatively controversial position on protein calories and it's this: protein calories don't matter and the body will just waste what isn't needed. Gluconeogenesis (conversion of protein to glucose) is a thing but it's driven by demand, not supply. There are a few good studies on the issue but this one is my favorite: https://www.tandfonline.com/doi/epdf...ue&role=button

They took a bunch of gym bros (IMO the only cohort that can be reliably counted on to do a good job with food/macro logging) and randomized them into two groups, one averaging 1.8g/kg/day (about 138g) and one averaging a ridiculous 4.4g/kg/day (about 307g) for 8 weeks. The high-protein group consumed around 800kcal more per day (including so-called protein calories) than the normal-protein group and still lost fat mass.

[Dantheman]

For de novo lipogenesis (creation of new fat from carbs) to take place you have to go HAM on the carb intake - like in excess of 400g/day while being completely sedentary.

This is correct if you are insulin-sensitive. Per this Peter Attia interview with Gerald Shulman de novo lipogenesis ramps *way* up in insulin-resistant individuals (which is probably a very low percentage of people reading this thread, but a huge percentage of GenPop): https://podcasts.apple.com/us/podcas...=1000586933595

[bean]

This is correct if you are insulin-sensitive. Per this Peter Attia interview with Gerald Shulman de novo lipogenesis ramps *way* up in insulin-resistant individuals (which is probably a very low percentage of people reading this thread, but a huge percentage of GenPop): https://podcasts.apple.com/us/podcas...=1000586933595

That's a great interview. That they can induce insulin resistance in minutes with lipid infusions is amazing.

And yes, my bias and perspective is focused towards healthy/athletic people because that's where I am and there's also complexity and nuance to things. For T2Ds it's really simple - cut out the carbs, eat less in general, and get on a regular exercise routine.

[J. Barron DeJong]

This is correct if you are insulin-sensitive. Per this Peter Attia interview with Gerald Shulman de novo lipogenesis ramps *way* up in insulin-resistant individuals (which is probably a very low percentage of people reading this thread, but a huge percentage of GenPop): https://podcasts.apple.com/us/podcas...=1000586933595

I may be misunderstanding, but you’re saying that excess carbs in this case are not being turned into stored fat?

Does that mean the carbs aren’t being absorbed by the body at all, just passed through? Or are those extra carbs being used for metabolism and displacing fat use?

[Dantheman]

Or are those extra carbs being used for metabolism and displacing fat use?

Nailed it. If you're insulin-sensitive excess carbs don't get turned into fat unless you are eating almost no fat and eating a metric shit ton of excess carbs. But, if you are insulin-resistant you'll turn excess carbs into fat quite easily.

[bean]

I may be misunderstanding, but you’re saying that excess carbs in this case are not being turned into stored fat?

Does that mean the carbs aren’t being absorbed by the body at all, just passed through? Or are those extra carbs being used for metabolism and displacing fat use?

If you're insulin-resistant you're more prone to turn carbs into fat.

If you're lean/fit/active consumed carbs are more prone to be used for energy.

[climberevan]

Mixing bottles for tomorrow's race. It will be 6 hours-ish. 500g of sugar in bottles and another 2, 100g bags for refills in case I'm slow.

[XtrPickels]

Damn - Bean Dropping knowledge and Dan coming in with the 1-2 punch.

[bagtagley]

Damn - Bean Dropping knowledge and Dan coming in with the 1-2 punch.

Agreed, really well explained.

For the insulin sensitive, what happens to excess carbs, typically? Are you all avoiding fat intake when you’re drinking sugar water?

[bean]

For the insulin sensitive, what happens to excess carbs, typically? Are you all avoiding fat intake when you’re drinking sugar water?

The gallon and a half of blood we have only carryies about 4g of glucose at any given time which means anything we eat has to get used or stored. If you aren't generally overeating (which if you're insulin-sensitive, you aren't) you'll probably have storage capacity in your muscles and liver. Fructose intake specifically goes through the liver (though 25-50g can be directly absorbed in the small intestine) and so chronic excessive fructose consumption can lead to NAFLD - but it's less of a concern in fit active people.

For me slamming sugar is an infrequent thing on big rides/mountain days and in those cases eating fat isn't going to help performance. In day to day life I try to avoid mixing fat and carbs (especially sugar) too much, but that's not to say I don't have pizza and ice cream with the family sometimes - incidentally two of the most easy-to-binge foods on the planet.

[fool]

The vast majority of body fat is stored dietary fat. For de novo lipogenesis (creation of new fat from carbs) to take place you have to go HAM on the carb intake - like in excess of 400g/day while being completely sedentary. The rapid swings in weight from carb restriction/consumption are changes in water weight. So if you want to get super lean, look to what bodybuilders do on a cut - high protein, moderate carb, low fat, along with good amounts of base-level cardio. Low fat intake means there's not much that can be stored. And the low-intensity cardio primarily burns fat.

Thanks for this, Bean. The whole post was great but this in particular is super insightful. I’ll start adjusting my diet accordingly. I’d like to get more lean - maybe lose 5-10 pounds - and currently doing 3 hours of strength and 6-10 hours of riding/running per week. Any good, readable books that cover the basics more in-depth? Would love to read a well-written book that has the latest reserach/studies in a more reader-friendly format.

On the diet note, does anyone have any favorite non-whey protein powders that are sold in bulk? I eat meat/dairy but I don’t think my body loves whey (though iirc it’s a slightly more effective protein powder than alternatives.)

This is correct if you are insulin-sensitive. Per this Peter Attia interview with Gerald Shulman de novo lipogenesis ramps *way* up in insulin-resistant individuals (which is probably a very low percentage of people reading this thread, but a huge percentage of GenPop): https://podcasts.apple.com/us/podcas...=1000586933595

I just got my A1C measured - 5.1 - so based on Attia, it seems like I’m good on insulin sensitivity and type 2. If anyone has other thoughts on those numbers, I’m all ears.

In day to day life I try to avoid mixing fat and carbs (especially sugar) too much, but that's not to say I don't have pizza and ice cream with the family sometimes - incidentally two of the most easy-to-binge foods on the planet.

Is this avoidance based on biological mechanisms or (easier) emotional control on consuming carbs and fats more deliberately? It sounds like the latter.

[Supermoon]

On the diet note, does anyone have any favorite non-whey protein powders that are sold in bulk? I eat meat/dairy but I don’t think my body loves whey (though iirc it’s a slightly more effective protein powder than alternatives.)

I use orgain which is vegan and relatively cheap from Costco.

[bean]

Any good, readable books that cover the basics more in-depth?

…

Is this avoidance based on biological mechanisms or (easier) emotional control on consuming carbs and fats more deliberately? It sounds like the latter.

I don’t have any book suggestions, I’ve mostly built my knowledge and opinions through the internet. Lots of little pieces over a couple decades. Your three hours of strength is plenty and my opinion on cardio stuff is, generally, one hard workout a week, one long endurance session a week, and then as much base volume as you can fit in. Life throws too much at me to try to stick to some complicated training calendar, but my “plan” got me to a sub-3 marathon, sub 9 Leadville MTB and had me on track for probably a 22 hour Leadville run if my knees had held up.

I’m not fully up to speed on all the hormonal interactions that make it way too easy to eat an entire pizza followed by a pint of ice cream but it’s clear from looking at the general population how dangerous ultra-processed hyper-palatable foods are and how easy it is to overdo it. There’s clearly more to it than carbs+fat together = obesity or the French would be a profoundly unhealthy population. I just try to pay attention to it when I’m planning what I’m going to eat.