High Carb intake a risk for diabetes?

Whilst I appreciate the calorie benefit to training I am a little concerned that all that mega- carb intake ( pre, intra and post ride) may cause health problems in future me. Thinking inflammatory diseases such as rheumatoid arthritis and vascular diseases ( through inflammation of vessels) and of course diabetes.

Can anyone reassure me that this is an unnecessary concern?

I have type 1 diabetes, and as long as my carbohydrate intake is centered around my training, my insulin sensitivity remains high and my blood sugars remain in control!
And by the way I’m on the extreme high carb intake end of things during training at upwards of 140 to 150 grams of carbs per hour during high intensity training!


Score 1 for reassurance. Might I ask how old you are? ( I am 50 and I’m beginning to look at the next phase of life with more circumspect).
As a type 1 diabetic your insulin is all exogenous.
My concern with a high carb intake is “burning out” the pancreas and so turning me into a diabetic too?

I think it’s going to be individual. How are your numbers? Personally, I think some people over do it. You don’t need to slam carbs before, during, and after every easy workout. Before a workout, glycogen stores should sufficient from your normal healthy diet. Fueling during a ride seems like a good strategy because the glucose is taken up directly by the muscles with maybe less impact on overall metabolic health. Post ride, you need protein and carbohydrates from your normal food. You don’t need to eat a gel after a ride.

You can also periodize your carbs. For an easy endurance ride, you can probably just do that on normal food - no need to drink sugar. If you do one or two interval sessions or a race per week, then you can fully carb up for just those sessions.


Yes I like your approach, it sounds sensible. Despite the much talk about high carbs to fuel rides, recovery drinks etc, I do think that as we get older we move from racers to riders and our carb intake must reduce accordingly

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There are always risks but being active and not obese is a good way to fight off many diseases/conditions. None of us have crystal balls or can predict the future or what effect it will have on you.

If you’re fuelling the work correctly I can’t see that diabetes should be a problem - risks are listed on various sites but consuming a high carb diet isn’t listed as a singular risk factor in itself from a quick look though being overweight is.

Do some research and question the validity of what you find. If you think there are risks then change what you need to address those risks. In truth you may already have a genetic disposition to something and none of us would be able to predict that.

I’m 55 and fuelling with various foods depending on the intensity of the ride/workout. I feel way better fuelling harder rides with a home made mix than the flapjacks on the longer days but it’s always a caloric defect until I get home. :grin:

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If you’re concerned (and I think more athletes should be), buy a blood glucose meter and do some spot checks. Most meters come with 10 or 20 strips to get you started, and it’s cheaper than a single doctors appointment. Things you’re looking for: <100mg/dl 2 hours after a meal; post-meal peak of <160mg/dl; fasted morning reading <100mg/dl. Be aware that exercise can raise you blood sugar levels even if you’re not eating.


Type 1 diabetes is an autoimmune disease from damage to the insulin producing cells, which differs greatly from type 2 diabetes associated with loss in insulin sensitivity thought to be caused by carbs. They really shouldn’t even have the same name.

Now in terms of carb risk to diabetes development insulin doesn’t spike from carbs taken during exercise so there is likely minimal increase in risk there.

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Diabetes isn’t caused by carbohydrates.

I repeat, diabetes isn’t caused by carbohydrates.


Exercise causes insulin-independent glucose uptake in the muscle cells. As such, high sugar intake during exercise will not increase your insulin resistance.


What makes refined sugars unhealthy is if you eat too much of them. That is not the case if you consciously consume them during or around your workouts, staying within the limits of what you can absorb per hour and what you have burned during the workout.


I’m wondering if all that demand on the pancreas to produce insulin can eventually “burn it out”?

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low-med gi carbohydrates of no concern. very beneficial.

high gi carbohydrates (all gels, maltodextrins, sports nutrition generally) of very high concern. use these sparingly and only when necessary. high risk of atherosclerosis, inflamation, pre-diabetes.

if concerned you might try a constant glucose monitoring system for a month or two. otherwise, learn the gi levels of foods.

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Now your view is very different to some others expressed above and it does echo some of my concerns i.e. inflammation etc.
I am well aware that the TR coaches are strong on high carb diet and fueling; I am just beginning to wonder if that advice should be stratified according to age? Is it “no worries " for the young and otherwise healthy athlete, but " a significantly different approach is needed for the ageing, say > 50years” ??
I wonder if coach Chad has some insights here that can lead to either reassurance or reassessment?

Tim Noakes raised this on a recent Fast Talk Podcast.

He seemed to think it could be an issue, and that people overconsume sugar and carbs in general.

He’s from more of a running background so framed it as ‘people running a 4 hour marathon don’t need high carbs to do it’, which I’d interpret similar to those above, i.e. you don’t need a load of bars, gels etc to get through an endurance ride.

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I am Pre T2 with shockingly bad family history. I wear a CGM all the time. T2 is a long term energy surplus disease. Carb restriction can be used to mitigate the acute symptoms but does not treat the underlying root cause.

If you are not showing signs of metabolic syndrome, you frequently exercise with high and low intensity and are vaguely in energy balance there is nothing to this, dont worry about it.

If you have a scary family history or other reason to think your insulin response may be abnormal, wrap your carbs in exercise or fiber. If I have a bowl of white rice, my glucose goes to high and the overproduction of insulin often but not always makes it go too low. If i have the same rice and get on the bike, it does not happen. If i have a big handful of carrots and add some form of fat to the rice, the effect is blunted significantly.

The carbs are not the problem but the delivery rate can sometimes be not ideal. Fat, protein and fiber all slow the rate.

Exercise opens up a physical pathway for cells to take up glucose and it can work much faster than the chemical pathways. This means you can take up all that glucose without any insulin being added by your beta cells. I can drink country time pink leomaide 10 min before, during and up to 20 min after without any major glucose excursions. If i tried that outside of a workout i would feel like crap for 4 hours.

So, to sum all this up: Eat full meals made of actual food. Dont make a habit of eating pure carb things by themselves (without some fat or protein or fiber) unless its around a workout. Treats every once in a while wont kill you, ice cream and beer all by itself every single night just might.

btw, beer does odd stuff to blood glucose. I only understand 1/3rd of what I am seeing but it has resulted in me drinking more athletic brewing company IPA and a bit less (but not none) real IPA.

If your A1c is even a little high in the pre range ask your dr for a CGM script and wear it for a month or 2. You will learn so much by watching your body respond to stuff that this will all become super obvious.


Very interesting and useful information, clearly gained through experience. Thank you for sharing !

This is my first year being conscientious about fueling rides and workouts. I take in anywhere from 20-80 grams/hour on the bike. Mostly by energy drink – a 1:1 maltodextrin to fructose mix. Toss in fruit, dates, and gels occasionally. I had my annual physical about 1.5 months ago and my A1C reading was good, my instantaneous blood sugar was borderline.

Away from the bike I strive to stay away from the high GI stuff. However I eat alot of white rice and the wife is a temptress and knowsy weakness for oatmeal cookies–with raisins!

I’m a mid 50 yo guy who started cycling late in life.

This is your N+1 report.

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When I go out on endurance rides I definitely reduce my rate of carb intake, but never to zero.