Nutrition plan for long event - fat oxidation rate?

Hi,

I am looking to do a fairly long race next week (Mallorca 312, around 10h on the bike).
I am looking at my nutrition strategy for this one, ie carb intake through bottles, bars and gels vs carb expenditure.
One of the variable to be fairly important is the fat oxidation rate. While looking at research papers, I am finding graphs like this:

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Or like this:

that seem to be pretty much what I am looking for to approximate my fat oxydation rate given my cycling ability (Vo2 max) and intensity at different moments of the race (climbing mountais vs riding in a peloton). And hence better approximate how much I will need to fuel at the different moment of the race.

The only issues I have are:

  • While I am finding a few graph, I have been unable to find any actual tabular values, even less so for trained cyclist.
  • How accurate are those values, are we talking ± 10% or this is so much person specific that unless a test is done this is completely useless?

Thanks!

Why do you want to know this? My take on nutrition on the bike for events like this, is as much as my stomach can handle per hour for the duration of the event.

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There is a lot of variability between people as to what substrate (fat vs carbs) makes up what percentage of energy requirement, at a given percentage of VO2max (or FTP).

In this paper the average point at which glucose became the predominant fuel source for submaximal efforts was 58.4%…

PLUS OR MINUS 21.1%!!! (so the range of values was ~37% to ~79%)

You would not be able to look at an average value for a sample of athletes and expect that this average would apply to you in a meaningful way.

If you have recent data about yourself somehow from lab testing, this could be useful.

I routinely do long/multi-day events, as this is the focus of my cycling. The goal of nutrition during a race (rather than during training) should be to consume as many carbs as possible, the whole time, regardless of what you calculate your energy requirements to be. Consuming sweet things reduces RPE independent of its calorie content. And it is unlikely that you’d be able to consume as many calories as you burn during the event anyways.

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Hahahaha this is the appropriate reaction to that variability range! Also +1 on carbs, carbs, carbs. There are great, simple recipes for making your own cheap carb mix all over this forum.

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Ah yes that is what I was expecting.
I am already making my own drink mix with maltodextrine and fructose, and regularly train with 100-120g/h.
My reasoning was also to check if my target powers on climbs (first half has 5,000m of elevation) vs my level and assuming this rate of fueling would have any chance to work or would lead me to bonking inevitibly by the end. I am not sure i want to significantly increase the fueling even if the last GCN video seem to suggest that now up to 200g/h could be ok.

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No matter what you do, you will be in a deficit. You can’t oxidize fat or consume enough carbs to not be spending more energy than you can create/replace. So, eat as much as you can.

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If I could ask, what is your average weekly volume and your average daily total carb intake?

Details aside, I wouldn’t be messing with your nutrition at this point. It’s a week away- stick with strategies you’ve trained with and what you know works. Depending on the race, your effort loves and when you’re able to take a drink might also be dictated by the terrain and those around you, so I’m not sure you’d be able to achieve that level of granularity in practise- as long as you’re getting something in regularly I think there are more impactful things to worry about.

If it’s something you want to work on, use this race as a baseline/learning opportunity to tweak your strategy in the future. Individual variations and practise matter hugely when it comes to nutrition, and experience is as good a teacher as any graph.

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Right now? It would probably average around 400-500g/d of carbs depending on what I’m eating and if I’m working or not. I’ve been doing ~15h/wk this month. It was closer to 10-12h/wk for much of the winter.

Interesting, forgot to ask your weight for reference.

I’m 65kg. Usually have ~250g carbs a day, except the days I do big rides where I do 400-500g. I’ve been trying to go lower on normal days but recovery gets affected. I’m doing about 10h a week. 5-6h of the in one ride.

I’m 79kg this morning.

250g/d of carbs seems maybe low on first glance? I think that’s almost less than the RDI for carbs for an inactive 70kg male. Ballpark rule I’ve used is take your total daily caloric intake, multiple by 50%-60%, then divide by 4 to get g/d of carbs. I’m typically averaging out to 3000-4000cal/d, which would be around 400-600g/d of carbs with that math.

Perhaps. If I were to up the volume and or intensity. I for sure would have to add 50g.

Personally at 8-12 hours/week, my target is 6g/kg of lean body mass (which I estimate at 75kg) or 450g of carbs per day.

Based on a number of sources, randomly pulling up this one first:

And this one:

https://www.gssiweb.org/docs/default-source/sse-docs/sse_231_005.pdf

has some good pics like this:

and a few others.

Yes, your numbers align with what I read

image

Regarding your lean body mass. Unless you do a proper DEXA test, you’ll likely underestimate your body fat. 20% is for a normal looking somewhat lean person. 25% -30% for a more robust person.

I’ve taken a very detail look at my nutrition, measuring everything and standardizing procedures, you would be surprised how the data differs from our perception.

Looking at my records from April, I’ve averaged 277g/daily. Averaged is pushed up by 3 big ride days where I consumed 550g.

Macros: 20% Protein, 35% Carbs, 45% Fat

I haven’t been this lean and muscular since High School.

Average 4.2g/bw….higher if I did lean mass. If I was 20y younger and all I cared was racing, I’ll probably maximize this, but I have competing interests with heart health. So trying to find a minimal effective dosage.

Estimates aren’t that hard, didn’t bother with a Dexa test. I simply used high school / freshman year college ‘not an ounce of fat on me, and generally considered skinny / not muscular’ weight. Have zero performance issues while training and am not guzzling carbs on the bike for workouts under 2.5 hours (fueling around 40-60g/hr depending on lunch carbs). Above 2.5 hours, yes, I’ll front load carbs at 90-120g/hr. Setting power personal bests that haven’t been touched since 2017 when I was ‘I can’t drive 55’ yrs old - a little shout out to Sammy Hagar :metal:

I’ve been wanting to loop back and verify my own carb consumption, so thanks for bringing this up.

According to wikipedia Chris Froome is my height (186cm) but only 68kg and he has no upper body mass. So likely less than 20%. Lets say 10%, so that puts his lean body mass at 61kg. Around 16 years old I hit 186cm but was skinny and weighed a little more than 68kg, hmm.

Now lets say Froome is only doing moderate exercise program, averaging out to an hour a day, or 7 hours/week. ACSM recommendation is daily carb intake of 5-7g/kg per day.

Now 5-7g/kg is actually fairly generous around 60kg, here is a chart I made:

so I’d say Chris Froome should be eating around 300-420g of carbs a day.

Lets say I have at least 5kg more muscle on my body versus Froome, that would put me around 65kg and not the 75kg of my early estimate (using 4-6g/kg/day). That puts me in the 325-455g/day range, its a pretty big range. Looking at my calorie/macro tracker

I’ve been roughly in the 300-450g/day range. Haven’t been tracking EVERYTHING, everyday, but on the days with compete data its 300+ grams.

Thanks for bringing this up! I’ve wanted to verify what I’ve been feeling is in fact matching up with the recommended range given my endurance focus and average 7-8 hours/week volume.

You don’t disclose your weight. So let me go ahead with 3 scenarios, based on 400g, since you don’t record everything, likely you are closer to upper boundary.

80kg > 5g CHO per kg
85kg > 4.7g CHO per kg
90kg > 4.4g CHO per kg

Which is fine according to guidelines. :+1:t3:

I’m at 4.2 and in the process of lowering. I’m training 10-12h a week, 2 intensity sessions, one easy Z2 and one big ride in the upper half of Z2, plus 2h of lifting in 3 sessions. This is sustainable for me with 4.2 g CHO per kg, but I think I can get away with less without affecting quality of workouts and recovery

Here’s the rub, the more you consume carbs, the more your body uses them. That tells me that there’s likely a lower optimal.

Given that you don’t want to do DEXA, I’d forget about fuzzy calculations of body fat. Given your age and likely weight you are between 25-35%.

Carb consumption recommendations are based on lean body mass, not total weight. Carbs are stored in the muscles and liver. I could be 175 or 200 or 225 or 250lbs with the same muscle mass. Same muscle mass, same storage capacity. Somebody correct me if wrong.

This highly cited paper, where I got the table I posted used body mass

Carbohydrates for training and competition
Louise M. Burke , John A. Hawley , Stephen H. S. Wong & Asker E. Jeukendrup

Furthermore, did a cursory search of glycogen storage and all the papers I saw in PubMed used body mass for their calculations.

As an aside, here’s some comment from Jeukendrup:

The composition of a diet should depend on the goals of the athlete, the goal of a workout, and the individual’s makeup.High carb or high fat? We don’t need to choose one OR the other. We can have BOTH and this will allow us to develop our fat metabolism as well as carbohydrate metabolism. Let’s develop the art of integrating nutrition and training and not see them as two different independent entities.What you eat and how much you eat should depend on what you just did and what you are going to do. Sometimes an athlete may want to “train low” (train low refers to low carbohydrate in the diet and/or during training) to make sure fat metabolism gets challenged and ultimately optimized. Other days an athlete may want to train high intensity, focus more on quality or train the bodies capacity to absorb carbohydrate. Those days there should be a focus on carbohydrate, before and during training. Why would you do the same thing over and over again, day after day?

which stated the following:

“Estimations of the amount of carbohydrate required to replenish glycogen stores and to consume during exercise as a supplementary fuel source should consider the mass of the exercising musculature (using body weight as a proxy), with a sliding scale according to the training or competition energy cost (Table II).”

Its actually stated twice in that paper.

The estimates you are using are scaled to muscle mass, and use body weight as proxy. Everything I said above holds true about excess weight - forget about it when considering carb consumption, and instead use lean body mass.

And yes, I’m totally with you on varying carb consumption according to workouts.