Keto Targetted Carbs for Workouts/Races

I’m currently testing out a keto diet, with a view to making it a ‘targetted keto diet’ once fat adapted. Couple that with the ability of Xert to report estimated fat/carbs burnt, I’m wondering if there is a way to use the Xert info to plan pre, intra and post ride carb requirements.

The objective is to have enough carbs to properly fuel the workout/race, but no more, so as to get back into a fat burning state ASAP.

Anyone have any ideas, thoughts, experience.

I’m hoping by looking at past similar rides, I can use this to plan future carbs, eg. a VO2 workout, Zwift race or long weekend group ride. Take for example the two rides below from my Xert history:

Group ride, 3 hours with a few 10 min climbs:

  • Calories 1626
  • Carbs 191g
  • Fats 86g

60 min zwift race:

  • Calories 662
  • Carbs 70g
  • Fats 38g

Have you had a look at “Eatmyride”? I noticed Harry Sweeny of Lotto Dstny using it during his preseason which had an app that can be used in realtime when on the bike. It had a carb burn rate on it so he knew exactly how many carbs to eat relative to his workload.

If that is any help?

[quote=“asillars, post:2, topic:42709”]

Interesting, eatmyride seems to give you a ‘carbs per hour’ estimate, differs based on inputs, eg. carb loaded or of some use, thanks.

I want to start off by saying I am not an expert on carb/fat utilization and fueling, or keto, but I will explain what I do and why.

I use past rides and the Xert carb estimate in the workouts as a source of data. I use that data and the the number I calculate from the chart below to make a decision. Also, I think there is some personalization required depending on how much carb you can physically consume.

Based on your long ride data, you burned 191g/3hr=63g/hr of carb. From the chart below, it recommends 60-90g/hr for 3hr rides. The numbers seem to correlate well at the lower end of the range. I personally would try for the higher end of the range to maximize performance, but you would probably be perfectly fine to fuel at the lower end of the range.

For the 1hr Zwift race you burned 70g of carb. From the chart below, for a 1hr ride, it recommends up to 30g/hr. You would probably be okay with nothing, but personally if it is a really high intensity ride, I try to consume 20-30g of carb about 15 minutes ahead of the ride and that is all (something that is quick for your body to absorb like a gel, and I’ve recently been drinking grape juice). If it is a moderate ride, I try to consume between 30-60g/hr. For me, the decision comes down to how much I can physically consume due to the intensity.

I don’t remember where I got this chart from…but I think it has to do with the fueling required over given excercise durations to ensure you don’t use up your stored glycogen. Please note, the body seems to be able to absorb a maximum of 60g/hr of glucose without causing gut distress, anything above this is recommended to be a different source, mainly fructose.

Hope this helps, and I would be interested in what others do.

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Interesting, therefore for a one hour intense workout, or zwift race only a small amount of quickly absorbing carbs are required, timed quite close to the race.

Since posting I’ve heard on a podcast estimates of:

  • Pre ride 1-4g per kg body weight
  • Intra ride 60-90g / hour
  • Post ride 10-12g per kg body weight over 36 hours

I’ve also listened to targetted keto atheletes having some carbs post exercise, but from something like purple potatoes, chickpeas, etc.

I assume if I had 60g carbs before a zwift race/workout, then I wouldn’t need anything the ride.

IIRC this is a graphic from Precision Hydration. Someone correct me if I’m wrong.

yes, I’ve heard this as well. Anecdotally, I have found 1g/kg/hr for each hour before the race to be a little too much for me as it feels like i still have too much food in my stomach. This year I’ve been trying 0.75g/kg/hr before the race and it seems to be a good amount. I am 71kg, and try to fuel 3hrs before the race, so I consume around 160g of carb. As part of this, I try to eat easy digesting carbs, which includes some grape juice.

Anecdotally, my goal is to eat my daily calories, plus the kilojoules I burn biking. On biking days, I try to consume 1.65g/kg of protein, 0.75g/kg of fat, and the rest low GI carbs (other than the easy digesting carbs pre-ride). Protein and carbs are 4kcal/g, and fat is 9kcal/g.

Hope this helps.