Under fueling workouts and first century ride

I’ve fallen into the trap of teetering between training for performance and training for body composition. I’ve been training for a full Ironman and following the medium volume plan from the plan builder tool. My training varies anywhere from 10 hours to 17 hours a week. I feel that I am considerably under fueling my workouts but I justify it by maintaining my body composition that I desire. I intermittent fast (I know I should probably stop this but I have a streak of over 100 days on the Zero app haha) so my first workout in the morning is always fasted, whether it be a 60 or 90 min V02 max or sweet spot bike, or a 40-60 min tempo or V02 max run. On the weekends I’ve been training fasted for the most part, 2 hour long runs fasted, endurance swims fasted, etc. I’ve donr 3.5 hour endurance trainer rides without any fuel, just electrolytes. I never have not been able to complete a workut and I’ve been training this way for 4-5 months.

I did my first century ride about a week ago. I ate 1/2 cup of oatmeal and a banana before and all I had for fuel during the ride was a banana at mile 50. I was taking nuun electrolyte tabs in my bottles and had a few gatorade zeros. Overall I felt decent and averaged 153 watts with a NP of 160 watts. I weigh 145lbs/ 66 kg’s so 2.67w/kg for a century ride, no idea if this is decent or not. If I ever felt like I was fading, once I got some electrolytes in, I was good to go.

If I’m being brutally honest with myself, I know I am under fueling. I need to man up and start eating more but I justify it because I have been able to hit my power targets every single workout.

For those of you who have under fueled before and started fueling properly, what differences did you notice? Performance? Recovery? Mood? What changes did you make to your diet/fueling? Any tips to get past the body composition image issue and eat to fuel workouts/eat for performance?

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If you don’t start fueling properly, you are guaranteed one of two fates for your IM…1) a VERY long walk after you get off the bike, or 2) a DNF.

Part of your training is practicing and figuring out the nutrition you need on race day. Stop worrying about your body composition and start focusing on your race.

Your century ride was a wasted opportunity to practice your race day bike nutrition and see how you feel…did you get GI distress, etc.

Seriously…you are setting yourself up for failure unless you correct your nutrition routine.


Do you not listen to the podcast? If not, I’ll summarise Amber’s approach to nutrition and training for you:

  1. Don’t diet on the bike.
  2. Don’t diet on the bike.
  3. Don’t diet on the bike.

I am going to agree with the others.
You need to fuel for success. Body composition is not something to chase unless you are doing big hill type events.
It would be better to work on Improving FTP, under fueling will deplete you somewhere. How is recovery ? How is sleep? How is your mood?

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@Power13 I appreciate the feedback. Great point that the century ride was a wasted opportunity to practice race day nutrition. I think I just needed to hear it from someone else and get it through my head I need to start fueling for performance or I’ll DNF my race, which will be much more disappointing than any changes in body comp. Thank you for the input!

@Cavasta I just started listening to the podcasts. Haven’t heard this yet but point taken. Need to start fueling properly!

@C10oky I am doing the ramp test today after 8 weeks of medium volume base training on the full ironman training plan. My FTP is 204 so we’ll see what I test at today. I think this will be another data point to show me if I am siginifcantly under fueling. It’s hard to say how recovery is since I’ve been training and eating like this since the start of the program but I feel like it could be better. Going to try fuel workouts better and eat higher carb to see how my recovery, sleep and mood compares to before. Looking at all the elite athletes, they all seem to eat a high carb focused diet so that’s saying something. Thanks for the input!

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It might help to know what your daily calorie deficit is. You can probably maintain a 500 calorie deficit if you make sure to eat at the right times to fuel the work. It’s hard to say whether your are dieting or not without knowing what your caloric intake and expenditure is.

I recently started eating more during my rides and have noticed that I don’t come home starving and eat the entire kitchen. Here’s an idea: Just do ONE ride with adequate carbs and feel the difference, convincing your mind to only do a thing once is easier than convincing a whole habit change. Once you feel the carbs after that one workout it will be easy to adopt the habit, doing it for the first time is the hardest part.

I take a middle ground approach and try to do what pro’s do: go hard on hard days, go easy on easy days.

(1) get leaner (from 80kg to 75kg), lost 3kg. Aiming for 500kcal deficit per day, so far worked in first 3 weeks of build
(2) train for endurance (up to 200km).

Indoors, easy day (recovery, like Pettit): no recovery smoothie, no extra eating
Indoors, sweet sport: small recovery smoothie (50g oats, 1tbsp peanut, 500 ml milk, 1tbsp cacao, 2tbsp hemp protein, 1tbsp sugar).
Indoors, threshold and VO2max for 1h30: large recovery smoothie (75g oats, and 1tbsp hemp protein extra). Also eat extra carbs before often, and drink extra bottle (700ml) afterwards. Mealtime focuses on refueling more carbs.

Outdoors in zone 2: delay eating as much as possible. When doing 4 hour rides, I start eating 2 hours in. When doing 5-6 hours rides, I start eat 3-3.5h in.

For me that works.

Before you start completely changing your lifestyle and diet by loadng up on carbs have a read of this then come to your own considered, balanced decision. I say this because you are obviously very well fat adapted. https://www.amazon.co.uk/dp/0983490716/ref=cm_sw_r_cp_apa_i_xQwkFb9SD4ZNM

Chronic underfuelling can lead to pretty severe problems in the long run. You might want to read up on RED-S. Here are some links that might provide a good starting point for evaluating your eating habits:


Yeah, don’t do this :-1:


I’ve gone through this a few times. Here’s a few things I’ve learned. (Sorry for the wall of text, this is kind of a personal topic for me)

  1. just because you’re not experiencing negative effects now doesn’t mean they’re not going to pop up in the future. In fact, with undereating, it’s pretty much a given that they eventually will- and when those effects hit, they hit hard. A few years of RED-S pretty much ended my high school running hopes. I got faster until I didn’t. I’m still dealing with the physical impacts of that, like digestive problems, poor bone density/dental health, and fertility/hormone issues. (luckily the cardiac damage wasn’t permanent…)
    I’m not here to say everyone has an eating disorder nor that their case will be as serious as mine was, but it’s worth noting I was only undereating by ~700 calories at that time. I see people on this forum and others running a bigger deficit than that all the time, thinking it’s not that big a deal. But a significant deficit alongside a heavy training schedule is a massive amount of stress on the body, and IMO it’s only worth it if the health benefits of you losing that weight outweigh the potential consequences (i.e. if you have significant weight to lose or in the short-term before an event)

  2. You’re hitting your targets now, but you could probably punch way higher and feel a hell a lot of a lot better doing it if you’re fuelling adequately. This happened to me recently- thought I was eating enough, found out I wasn’t after bombing a really hard week. Fixed the diet and I’m hitting a higher pace/power during a heatwave than I was during the cooler days. I’m recovering way faster and my legs don’t hurt all the time. Mentally everything is just…easier, both when I’m training and in my everyday life. If there was a supplement that did that everyone would be taking that, and yet a huge amount of athletes aren’t willing to change their habits for those same benefits. It’s a bit depressing thinking how many gains I could have made if I was able to perform to that level for what…2 years now? Damn.

TL;DR: Humans are pretty good at getting used to feeling kinda shitty, and sometimes you don’t realize it until you actually feel better.


I have limited IM 70.3 experience (2 races). In my experience, I trained at 5-7 pounds heavier than my race weight until 2 months prior to the race, probably averaging 3,000-3,500 Cal/day to fuel the VO2 max and threshold workouts. When I transitioned to the specialty phase of training, where pretty much all the training is z2/3, and the durations go up, I was burning 3,500 to 4,500 Cal/ day and lost the extra weight without having to change my diet. Long story short, Chase the FTP gains at the beginning and fuel those type of workouts. As you transition into the sustained aerobic power and the workouts go longer and slower, the weight comes off. Just make sure to watch your macros and eat enough protein every day.


It doesn’t sound healthy to me… it sounds more like a downhill for injuries or something worse.

Take care of yourself


I guess the real question is how you are progressing. If you are getting stronger on your program that’s a lot different than if you are not. Also you said you are maintaining your body comp. if you are not losing weight that might be all right.

Personally I would buy a 50lb bag of Maltodextrin and a 50lb bag of fructose and start fueling your endurance workouts

I have been a competitive bodybuilder and can tell you that a ripped body is generally not a high performance body. It is a low energy (physical and mental) low performance body that looks high performance to our society. I was always cold when under 6% bf. High performance bodies that are ripped are usually well fueled and have been subjected to huge volumes of exercise.

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This is entirely my experience so give it whatever weight you’d like…

I was a fairly good collegiate distance runner but started to care more about the idea of becoming lean and light, rather than the actual performance. Ironically, it should have been the reverse, realizing that focus on performance would lead to an “ideal” body composition rather than the opposite. Anyways, I really f*cked up my eating patterns to the point where I was pretty much doing all of my training underfueld by substantial margins and also training a lot (100+ mpw). Now, 2 years after college, I’m still recovering from what should have been a quick injury thanks to imbalanced hormones and nutrient absorption and also tend to suffer from chronic anemia. I still train a lot but now it’s on the bike because my leg isn’t ready to run much yet. Eating has gotten better, but it’s very much a work in progress. So my first and main piece of advice is focus on your performance and let the body comp figure itself out. No one ever finished an Ironman and asked for your body comp stats, they ask about time, pace, watts (i.e performance based metrics).

As for things I’ve noticed when training while fueling vs not fueling, when I fuel during long efforts like centuries, I will recover substantially better and quicker than if I don’t. Like you, I’ve done long efforts like this with minmal fuel but they tend to lead to feeling like rubbish the next couple of days when I don’t fuel. You can also go harder more often (duh) when you eat because, ya know, energy. Lastly, I’ve found I’m substantially less irritable when I eat on the bike. When I’m chronically underfueld, I often get prissy and annoyed at even the slightest of things during a longer ride whereas fueling tends to keep me much more calm and relaxed.

Hopefully some of that helps!

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