Estimating caloric expenditure and fueling big days

Hi everyone

I am a long time lurker and first time poster. I’ve learned a lot from many of you over the years, and I appreciate all of you and this forum.

I am struggling to understand how to best fuel my long day in terms of the full period of time before, during, and after the ride.

I am a 36-year-old 66 kg male with about 20 years of cycling experience, mostly competitive. I ride between 15 and 23-ish hours a week plus a few longer base weeks on vacation, which has been consistent for the past three years or so. I love training and cycling and I have no overall issues with energy balance. I am self coached and follow a simple training plan with one to two hard days per week depending on what events I am targeting and when.

Lately, on my long day, I have been focused on 5 to 6 hour power. I have been completing these days with an average power of about 240 (250-260 NP, FTP around 340). I do 500-600 calories/h simple sugar for these rides, usually the basic blend, sometimes with some cornstarch or rice powder in gel form for variety. I feel that I mostly absorb this as long as I am mindful about fiber intake in the 12 hours prior.

However, after six hours, this still leaves me in the hole by almost 2000 calories, and it often feels like more if it is cold or whatever. I feel blocked at the end of these rides by energy balance. I think I could achieve more if I could just get more calories on board. The legs are hungry, but the gas tank is empty.

There are athletes who are able to sustain higher burn rates at around my body weight. How do people manage this? I have a very low-fat diet, which has worked well for me for years. Should I work on my fat utilization? I’ve never been tested but I’m probably nuking the glycogen right from Z2. Or is this just a limit of what my body is able to absorb and put out?

At 0.75 IF, you should be getting a good amount of energy from fat burning.

Carb loading and breakfast 3 hours before the effort should give you adequate padding.

I’ve heard of people waking up to eat and going back to sleep to get that 3 hour gap. Never done it myself though.

Yeah, sounds likely. For comparison: I am also 66kg, but much less powerful (at 4.2W/kg), usually consuming 160cal/h i.e. for 6h/IF=0.66 ride, 3000cal deficit and don’t feel anything bad or even particularly hungry after finishing.

Thank you, Svens. That is wild. That deficit would put me in a ditch! I think you are right.

Just remember that you’ll never be able to replace calories on a 1:1 basis…a deficit for rides that long is completely normal and expected.

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That’s solid fueling during the ride. You can try pushing more sugar if you stomach can handle it, but at some point you won’t be able to process it.

If you are riding with any intensity at all, you’ll never be able to eat as much as you burn during these type of rides. The good news is that you don’t have to. Since much of your fueling at that intensity is from fat, your goal with fueling is to offset glycogen depletion as much as possible. I’m personally not a believer in restricting carbs to force the body to use more fat, but some might suggest trying that. My suggestion would be to keep working the long endurance stuff and pushing the power higher on those long rides and keep pushing the sugar intake up until the body objects. The other thing I’d suggest trying if you are not already doing it - follow your aggressive fueling even for shorter rides. Besides constantly conditioning the body to process more fuel, you also reduce the chance of going into those big rides somewhat depleted from prior rides.

Big 6+ hour rides at high Z2 - low Tempo are a big focus of mine as I approach my target events (which are typically 6-12+ hours). Fueling is a big part of that training, but I find that those last hours get easier over time even with the same FTP and fueling. I’m not sure if that is the body using fat more efficiently or other fitness adaptations increasing my endurance, but I’ll go from feeling like I’m gonna bonk at 5.5 hours to feeling reasonably strong at 6.5+ after 4-5 weekends of doing that type ride on a saturday. That’s working up to around .8 IF for NP.

What time are you riding? It sounds like you’re primarily worried about the calorie deficit at the end of your ride? And are you tracking your intake throughout the day / week?

I have a lower overall training load, only 12-17 hours per week. But I’m 32 & ~63.5kg. In a 5-6 hour ride my NP can be 220-230. My last big ride like this was just over 4,000kj. I fuel this with 90g of carbs per hour in a Fructose/Maltodextrin mix so 350 calories/hour? Maybe I’ll stop in the 2nd half of the ride for a coffee and pastry for another ~500 calories.

I’ve found on a day like this I’ll feel best if I’m having breakfast, then brunch and other snacks. Maybe 7-8am I’ll have pancakes. Then 10-11am I’ll have a big bowl of oatmeal. Eating a lot of jam, peanut butter, etc. as toppings. I’ll start riding around 12. Ideally I’ll have as much as 1500 calories in my system before I’m on the bike. I’ve found that I can start a Z2 ride feeling full, and it doesn’t impact my ride. The intensity isn’t so high that a full stomach is a problem.

Getting off the bike I immediately start eating again. Protein shake, snacks, dinner, more snacks. Great day for potato chips, ice cream, etc. And even then I still find I’m in a slight deficit before bedtime.

Eating enough can turn into a part-time job with a high training load.

Thanks a lot everyone for your responses.

Upon reading everyone’s thoughts, my hypothesis is that I am waking up behind the eight ball and never really getting in front of it. I don’t eat much at night because I usually am not particularly hungry, as opposed to the mornings where I can pack it away no problem. I am going to take 200 g of carbs and move it to the night before.