High Carb intake a risk for diabetes?

If you guys with better brains/educations than mine could humour me here-

Just thinking out loud here on the whole Glut 4/exercise translocation thing.

Am I right in thinking it happens at even quite low exercise intensity?

And am I right that one of the problems with using insulin for treating diabetes is that you are in effect ramming glucose into cells that are already full?

So- how does it work when you stimulate Glut 4 transporters with exercise and the cells are likewise already “full”? (Thinking abut sedentary obese people specifically).
In effect, is there a mechanism by which insulin is pro-active and exercise induced translocation passive? Ie insulin can “overfill” a muscle cell but exercise will just keep the pathway open as required?

I’ve been trying to explain to a diabetic friend in his 70’s how important exercise (and diet) is to moderate his blood sugar is and I was just wondering if I’m missing something in my very simple understanding of the comparative effects.

I still don’t buy that Glut4 works in the absence of insulin. I do agree that we are more insulin sensitive when exercising, but insulin is required to open the door. The links posted above seemed to prove my point.

I think one of the biggest benefits of exercise is the increased insulin sensitivity after exercise has completed - for a period of up to about 36 hours I think based on what I have seen looking at my constant glucose monitor when I’ve used them.

Again, I think it comes down to genetic predisposition - some people are just a lot more prone to T2D, and yes, you still get T2Ds with BMI of 21 so if you’re worried, best thing is to have yourself tested as I describe above.

@Dr_Alex_Harrison… 300-700grams of sugar a day is crazy! 700grams of sugar is about 2,800 calories which is a LOT to burn. Glad you have a low HBA1C but for sure I’d never ever do this since I’ve become aware of my predisposition to T2D.

My point is that there is a behavioral aspect to it. High sugar intake for a recreational athlete may be harmless in the moment, but I know plenty of once great cyclists that are overweight or obese now because their habit of eating continued when their serious training stopped.

I’m suggesting that the median recreational cyclist likely doesn’t have the discipline to stop the sugar when they ride less or stop because of habit formations. Taste buds and the brain get desensitized to sugar. It just doesn’t immediately revert when your training goes down. There are plenty of studies showing how salty and sugary food are addicting and how overeating is a psychological/ mental health problem.
I agree that sugar improves endurance performance, but it is not a cost less benefit. There is always a trade off, that’s just the way life is. So that said, it might not be worth it for an average recreational cyclist to consume sugar as if they’re riding in the TdF because the benefit may not meet the cost

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Wait, why not?

Glut4 translocation from inside cell to outside cell is well substantiated to be caused by two things:

  1. insulin
  2. Muscle activity.

As long as you’re burning what you consume, when you consume it, there is no known risk.

I add the word “known” purely out of respect that we as humans do not foresee the future. But in non-researcher-speak… there is no risk.


A human body is a masterful thing at seeking homeostasis.

And I would never ever recommend it to someone with current or past blood sugar dysregulation. Just to be clear!

I’d posit that endurance athletes who become obese after their endurance career ends probably become so because of an unhealthy restrictive tendency for which the “on” switch was finally shut off.

If we collected data on these folks, I’d bet there is an inverse correlation between hourly fuel intake reported during pro endurance career, and pounds gained after career.

I posit it actually works in their favor. Drinking sugar water on bike → habituation of drinking sugar water on bike. Remove bike, remove sugar water habituation.

NOT drinking sugar water on bike → habituation of “eat everything in the fridge, off the bike.” Remove bike, habituation to eat everything in the fridge still exists.

100% correct. Did an experiment once. At 600g carbs post-workout, via frosted flakes. By the end of the mixing bowl of frosted flakes, they tasted like corn chips in milk. Can confirm!

It does, if it’s constrained to on-bike.

It does not if it’s not constrained to on-bike.

Yes. Overeating. Not drinking sugar-salt-water on bike.

We agree. No truer words. There are no solutions. Only tradeoffs.

We disagree. In fact, increasing, and then optimizing, sugar-salt-water consumption has been one of the primary ways I’ve been able to help endurance athletes lose weight and improve blood panel results. So much so that I made a couple memes about it.


I was surprised too, at first. Until it became such a reliable pattern that I could not get clients, no matter how thoughtful and well-written the rest of the diet plan was, to eat appropriate kcal around the clock, if they were under-fueling training.

Turns out, hypoglycemia during and after training has lingering hunger effects hours after kcal needs have been caught up on. Hypoglycemia also leads to reduced activity intensity, duration, and if experienced regularly, it leads to habitually reduced frequency of training, eventually.

Since body composition issues and inactivity, and not sugar consumption during and only during exercise, are the leading predictors of T2D, it turns out that I can make a very strong case that increasing, then optimizing, sugar consumption during training, actually prevents T2D in the endurance athlete population.

“optimizing” = somewhere between 0-140g/hr, depending on duration, intensity, body comp history, satiety needs, total weekly volume, + a dozen other things.



n > 500 endurance athletes.

PPS. Many folks still did not lose weight. Weight loss and future maintenance is intensely challenging. I’m not saying “drink more sugar and you’ll definitely lose weight.” Just pointing out a compelling correlation that is a large “n” to counterpoint “sugar during exercise causes problems.” I posit that when done optimally, it solves more health problems than it causes.


Agree with @Dr_Alex_Harrison on this one. I used to under fuel on bike then in the hours post ride was starving and eat anything and everything, usually junk! Now I fuel much more during the workout (just usually with sugar water and some squash for flavour) and do 20 mile runs or 3hr rides and come back and pretty much just eat normal (even though still calorie deficit at 90-100g sugar an hour). Just nowhere near as hungry so now just eat pretty constantly off the bike regardless of training (fairly stable and healthy diet) since on bike/run fuel so much more.


I no longer take in extra carbs on the bike on rides less than 2hrs. Unless you have a monster FTP and are doing >2hr rides, the math says you should be able to eat 2-3meals a day sufficiently to maintain expenditure or have a slight deficit without much challenge.

I’ve done the >100g bottles before and while I was fast (3.8w/kg and 314ftp) I was always insatiable 30min after getting off the bike. Since switching the intense hunger no longer occurs and I’m much happier for it


Yeah, I see a trend towards folks wanting to use >90g/hr for 1-2hr rides, and I think in 90% of cases, that’s inadvisable. In >50% of cases, much much less is better for shorter & easier rides.


Couldn’t agree more. I’ve alternated over the years from eating next to nothing to stuffing myself with carbs and in the process got myself totally confused as to what and how much to eat. Just prior to the pandemic I had a metabolic test done and to see what my FAT & CHO burning was. I’ve finally used that data to produce a spreadsheet where I’ve split my rides into the 5 zones and applied the average fat burning in g/min to those zones, added up the total fat burned and converted it into calories. In that way I get an estimation of the carbs burned on the ride. With an FTP of 226W I’ve found that on my Endurance rides I burn between 40 & 60g of CHO/hour depending on the intensity of the ride. I use the XERT Fat/Carb Garmin app on the bike and found that it under reports the CHO by a consistent 20/25g hr which I can obviously account for (I suspect the discrepancy is due to my particularly low efficiency in converting chemical energy to mechanical <20%)

. It’s not perfect but short of wearing a VO2master mask on every ride its the best i can think of.


Tl;Dr of this thread is it doesn’t.

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Yes, since I’ve started to be more specific about fueling on the bike, I’ve been eating much more healthily, less processed foods off the bike, without the excuse of eating junk to fuel.
It’s helped my training, helped me loose the menopause belly, supported my immune system.

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Worth listening to this: https://podcasts.google.com/feed/aHR0cHM6Ly9mYXN0dGFsay5saWJzeW4uY29tL3Jzcw/episode/NzVkNzQzNGMtYzM2Ni0xMWVkLTkyNTYtZjdhYmJiMWQxNDYz?ep=14