Hey everyone, I just did a VO₂ max test and wanted to get some perspective on my fat vs carb utilization, which came out a lot lower for fat than expected. Curious if this looks familiar to any others and what if anything they have done to alter.
Leading into the test, my training was very VO₂ max-interval focused. I’d been off the bike for ~3 weeks for family vacation in June then + sick with COVID in July, so I crammed in a lot of intensity in the 6 weeks ( two vo2 workouts per week mostly 4 x 4 or 30x30) leading up to this. Probably a stark reflection of that type of training and neglecting aerobic work.
I’ve got four kids (ages 2–7), so 90% of my rides are 1.5 hours or less, mostly commutes with some short climbs. I rarely get long base rides in, though I’ve always considered myself more of an endurance type.
Other health markers are all solid (8% body fat, healthy cholesterol, good glucose). But the recommended “training level” of 140 W at 134 bpm seems crazy — my power is usually over 250 W at 130 bpm (see below chart). Not sure how to reconcile that, except that I definitely need more consistent lower-intensity volume. Would welcome any thoughts!
Key Points from My Test (3 min each step at 40 watt power increases starting at 100 watts).
Fat Max: ~140 W / 134 bpm
Estimated FTP: ~350 W
Peak Power: 460 W (~5.6 W/kg)
Vo2Max: 64ml/kg/min or 5.22 L/min
Substrate Use:
At 220 W: ~24% fat / 76% carbs
At 300 W and above: essentially 100% carbs
Past ~380 W: 0 fat oxidation, all carbs
Body Composition / Health:
~8% body fat
Healthy LDL/HDL profile
Overall Profile
Very early shift to carb reliance
Fat oxidation drops off quickly compared to what I expected
What I’m Curious About:
How does my fat max compare to others with similar or different training backgrounds?
If you’ve improved your fat max, what training or nutrition strategies made the biggest difference?
Should I reduce carb intake? I ride mostly fasted when I commute in since its 5:30am but for intervals or harder weekend rides I will eat drink mix or some gels/blocks.
Thanks, I’ll give it a listen. No specific training goals right now other than stay fit, healthy and durable. These results just appear to me to suggest my fitness isn’t really built on a strong aerobic foundation.
The idea that my body needs such a high amount of carbs to do even z2 workouts seems less than ideal and maybe even unhealthy. But perhaps I’m overreacting and it’s just from recent training habits and will reverse if I change my training approach.
Honestly, when I read your post, it feels like a solution in search of a problem. You don’t state why you want to increase your fatmax. That’s a red flag for me. Also, your body fat percentage is very, very low already, so the purpose of fat utilization can’t (shouldn’t) be fat loss. Increasing fat utilization can be a method to increase performance under certain circumstances.
Let me summarize what I took from it:
You are extremely fit. 350 W FTP, 8 % body fat. That’s quite an achievement. If anything, if all you care about is performance on-the-bike, you may need to consider losing “unnecessary” muscle and gain a bit of fat.
Your weight (inferred from your W/kg) and body fat percentage suggests you are either very tall and muscular or you are very muscular.
You don’t clearly articulate any fitness goals.
The power at fatmax (in relation to your FTP) is irrelevant for training.
I’d flip it around and ask: What are your training goals? What performance metrics are relevant for the races and events that you do? Then go from there.
Thanks for the thoughts. I thought having a higher fat max was an indicator of healthier (body can rely more heavily on fat for harder efforts) and more robust (bigger aerobic engine) physiology. From listening to the podcast and feedback it sounds like it’s really not important other than being a byproduct of what you’re training for.
I’ve been doing mostly short vo2 efforts and then choppy rides (random surges over hills, etc) and very little constant z2. Maybe I shouldn’t be surprised that my body has shifted to that type of training and adaptability. I think all the attention on fat max over the years made me initially concerned. Perhaps I was wrongly thinking of it almost like lactate production where you want the curve as far to the right as possible.
I train for staying fit enough to enter a crit or road race one or twice a year. I’m not super tall, just under 6 feet but I do carry a lot of muscle. Thanks for the perspective.
It’s probably best for most people to have a good balance of fat and carb utilization (for being well-rounded, in general). The more fat you can utilize as you increase the watts, the fewer carbs you need to take in at that power, and you can maybe spare some carbs for a big finish, if needed. Doesn’t sound like it’s that big a deal for you, though.
I don’t have any idea where my fat max is. I’m not a high carb guy, but if I’m riding above low z3, I need to be taking in carbs, even on rides less than 2 hours.
If all you are interested in are the kind of rides you are doing now and crit races, increasing your fatmax is very, very low on the list of priorities, I’d say. Crit races have too much intensity and are too short to utilize a lot of fat.
Plus, and this is just a conjecture on my part, perhaps your low fatmax and your low body fat percentage are linked — your body simply doesn’t store enough fat beyond what your body wants to keep for absolute emergencies. In any case, the numbers you gave suggest you are a supremely fit individual. Why mess with what is working?
