Hi all,
I just wanted to share this study, just released today 21. January 2026. As a 60+ athlete and and former diabetes patient (in remission since 2024), I cannot overstate the value of this findings. I’m fat adapted, live a <20g/d COH and do not use any COH on any ride or event. But that’s just my personal N=1 experience.
Carbohydrate Ingestion on Exercise Metabolism and Physical Performance
It appears to say carbs before and during exercise will supply muscles with usable energy but you can get exercise induced hypoglycaemia anyhow. And something about fat as a fuel increases towards the end of prolonged exercise. This is just my uneducated explanation - don’t take it as anything serious. That was one long article of a lot of the same thing.
Carbohydrate intake during exercise helps mainly because it prevents blood glucose from dropping, not because it “refuels” muscles. Across more than a century of research, the review shows that:
Exercise‑induced hypoglycemia (EIH) is the strongest trigger for fatigue, while low muscle glycogen alone does not stop the body from working.
Eating carbs keeps blood glucose stable by reducing liver glucose output, even though it can increase muscle glycogen use.
Athletes adapted to high‑fat diets can perform just as well with lower glycogen, showing carbs aren’t an obligatory fuel.
Carbs improve performance even when glycogen is low because they eliminate EIH, especially in long events.
Overall, the real benefit of carbs during exercise is protecting blood glucose, which reshapes how athletes should think about fueling strategies.
It makes sense but it is somewhat different than saying taking in carbs spares muscle glycogen, which is what I have often read. This actually says the opposite. Still sounds like taking in carbs is a good thing which I can agree with.
Nothing new about not being able to replenish muscle glycogen during exercise or even using it less by ingesting carbs – Tim Podlogar has been talking about this for a long while. Similarly about bigger carb intakes actually increasing the use of muscle glycogen stores. My coach always prescribed eating slightly less carbs in the first 1-2h of a big race / workout to combat this.
One question I would have is, whether it’s reducing EIH or being used as fuel what difference does that make to the end user? If having X amount of carbs per hour is optimal, the athlete shouldn’t care too much about why it’s working.
I’m sure it’s still interesting from a research perspective.
The practical difference is your X would be different. They are saying preventing EIH only requires 15-30g/h, with no further benefits for higher intakes. Whereas the “fueling” hypothesis says more carbs is better up to the limits of your digestive capacity eg 100g/h.
I appreciate your healthy skepticism. It took me 6mon+ to get fat adapted and without taking this time, it would be likly to to have negative effects on performance. That one reason, why people are not changing. They are stuck in the CHO system unless they really see the benefits of breaking free. Suffering from health issues like depression (cyclist call it seasonal depression) and elevated blood preassure levels are often the first indicator. Diabetes is only detected decades later when insulin is no longer able to keep blood glucose in check. Adding some more decades, there is macula degeneration, Alzheimers, cancer and lots of other diseases potentialy lingering. Almost all are linked to metabolic disfunction which cann be triggered by overloading the body with sugar and starches.
The topic is not easy and touches on the acquired believe systems of us. Nevertheless, I made my risk analysis and concluded that I may be happily dropped in a group ride (or drop some of my fellow age group competitors) without consuming high amounts of sugar and starches (Maltodextrin) but keep my eye sight and a functional brain till I die. Hope to ride my bike till the day before this happens.
The current research does not point to high carbohydrate intake being a risk factor to depression, diabetes, alzheimers or cancer (or metabolic syndrome). In fact, national guidelines all over the world recommend that carbohydrates make up 50-60% of your daily calorie intake. What does increase your risk of metabolic syndrome according to current research is high BMI, abdominal obesity, low amounts of daily exercise and high amounts of saturated fat.
I’m not trying to change you or your thinking. I just wanted to share some new knowledge with fellow cyclists. In the end, it’s curiosity and the courage to question our current beliefs that help us gain wisdom and move forward on this journey of life.
Carbohydrates (CHO not COH) are not a cult that you have to break free from.
Every reasonable sports nutritionist I’ve heard talk about the issue has always suggested a sliding scale ingestion (small amounts of carbs on endurance rides to higher amounts for intervals to very high amounts for Tour de France racers).
The other thing is that carb ingestion should be matched to FTP. An elite with a 450 watt FTP is burning a ton of kilojoules just cruising around in their zone 2 at 300 watts. A mere mortal with a 225 watt FTP is burning way less carbs riding around at 150 watts.
People are getting type 2 diabetes, not because they exercise a lot and drink CHO, but because they don’t exercise and have a crappy diet and lifestyle.
Everyone is different- explore and see what works. I used to abide by the old rule of nothing but water during events less than two hours. Upping my CHO to 50-70 was a performance and recovery benefit, I’ll never go back to only water.
Got to love generalizations and one size fits all dogmas. nuance is often lacking, but often makes the difference. goals are an important factor and choosing how much or how little to partake in a particular practice and the extremity of your goals may affect both short term and long term effects. And everyone’s biology is slightly different.
Personally, I believe sugar helps performance. I used to max out intake for workouts and group rides. It helped or at least didn’t hurt. Particularly for longer efforts. Side effect for me was that I always felt extremely hungry. With some experience, decided not to max out carbs, maybe do 1/3 or 1/2 of what I used to do. I find I can hang with my groups fine and don’t think I’ve failed any workouts because of not fueling yet, but that may come. Anyways, much less hungry. So long story short. If you are searching for peak performance you need the fuel. Professional athletes are almost certainly NOT healthy as pushing yourself to those limits has consequences. If you aren’t trying to be a pro, then maybe don’t train like a pro, but also don’t assume that training doesn’t mitigate some of the health concerns that sedentary people with a bad diet experience.
Look up David Roche and the Leadville 100 trail run. He did a great podcast with Rich Roll and stated that he was able to break the record because of his ability to process a large amount of CHO during the race. I finished the Mohican 100k mtb race last year in 10 hours 25 minutes and felt good at the end (didn’t bonk). I was very tired but still functional. I couldn’t have completed that event without eating carbs constantly during the event. And if it makes any difference I was 70 years old.
The study in the OP isn’t just about low carb performance or keto or whatever. They’ve taken a bunch of well known studies that were used to form how carb and fat oxidation interplay, and parsed out of those studies (and the included data) a theory about where/what fatigue during exercise actually comes from and try to use the information in those studies to support their main hypothesis that the carbs you intake alleviate the fatigue you are feeling (as a result of low blood sugar) by satisfying some signaling in/from the brain, rather than oxidation of the carbs in the muscle alleviating the fatigue.
It’s very long (I’m only halfway through it), and covers a lot of different angles. You can tell by the names in the study that the authors are the usual big names of low carb. It seems to be a follow-up from the study that came out a year or two ago, that concluded you could, when properly fat adapted you can do whatever level of endurance on 10g of carbs/hr. They certainly do make a case for intake of carbohydrates while exercising, but how much is needed vs. what you can get from burning fat is what they are working through.
I’m not advocating for it, but am finding it interesting reading (including the historical studies they are reviewing as part of this study), and it’s all food for thought for a non-racing overweight old guy like me. I tried keto, and found no joy in riding my bike on that diet. Consistent intake of carbs since has certainly changed my riding, and trying to optimize how much and when, without overloading the system and possibly harming myself as a result is what is important to me now.
