Utilizing fat for fuel

The text below or something similar appears in most or all of the endurance workouts (from 60 minutes out to 4+ hours). I copied this out of Putuo which is a 4:15 endurance workout included in the full triathlon build. I can probably make it through a 90-120 minute endurance ride without any fueling, but doubt that I can longer than that. If I take in carbs (sugar), then doesn’t my body switch to using that for fuel rather than my fat stores?


“Aerobic Endurance workouts are aimed at improving your aerobic (i.e. non-sugar) power producing capabilities in a low-stress manner. By riding for increasingly longer periods of time, your endurance muscle fibers become more efficient at utilizing fat for fuel and sparing sugar stores for more intense efforts.”

Carbs are required to burn the fuel, no matter the type.

The trick is not to consume an abundance of carbs allowing for the fuel supply to switch.

Just wait, there’s better answers on the way!

I’d suggest this is debatable: Dr. Mike Eades - ‘Does Fat Really Burn in the Flame of Carbohydrate?’

But I do agree, if you’re going to bonk on an endurance ride, specifically one focusing on training fat metabolism, the trick is to take as few carbs as possible to make it through.

We’ve been told all our lives that we need sugar, must refuel every 20mins blah blah blah and now people are discovering that this isn’t entirely true. The thing is, it’s hard to switch our minds over to this, and we still convince ourselves that we need to fuel all the time when perhaps we don’t need quite so much…that plus it takes time to slowly build the endurance and fat burning/glycogen preserving. You won’t suddenly be able to go 2 hours if you haven’t before…but you may go 2hrs, then 2:15, 2:30 an so. Keep training and eating a lower glycemic/lower and better carb diet and you will improve vastly.

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Loads of good content about this topic from Coach Chad on the pod. I recall a recent conversation in terms that made sense to me :thinking:.
Your body does not a switch from fat to carbs at a certain intensity level. But gradual supplements the fat burning engine with your carbs burning engine, as the intensity level increases.
That individual intensity level depends on your fat burning engine capacity. So even though you might need to take on carbs during an endurance intensity workout, you’re still using and enhancing your fat burning engine throughout the workout.


There is a new calculator out for cyclists which works out your fat use vs glycogen use for each ride. Cant comment on its accuracy. link https://goo.gl/zRGui8

As mentioned, you burn a mixture of Fat & Carbs (not solely one or the other, generally) and this ratio changes given on intensity, duration etc.

Check my post here for an insightful article in to how fuelling affects this preference.

Ingesting a mixture of carbs & fat during your rides and tailoring this to both the length and profile of the ride can help reduce your dependence on carbs. As can not consuming lots of quick carbs prior to a ride.

I.E. on a long ride: fuel geared with a fat bias and switch this to a carb bias closer to the end. If your ride is quite sedate with maybe a climb or two then fuel more ‘carb heavy’ around (before/during/after) the climb or efforts.

A progression for this could be to switch from ‘fast’ carbs, to more moderate or ‘slow’ carbs. Then to begin introducing a mixture of moderate/slow carbs & fat.

I think a fair part of this is mental too, believing that you will or should ‘bonk’ if you don’t ingest Xg of carbs per hour.

I regularly complete endurance rides in the region of 4hrs fully fasted. Having a good resilience to bonking is quite nice. I have found on century rides where I have under-fuelled that I don’t bonk but rather my power reduces inline with my aerobic threshold and producing or holding much more than this for more than a short duration is quite difficult.


Thanks for the responses everyone.

You can train the body, it takes time.