Too low of body fat?

Is there a point as a cyclist that body fat can get too low?

I’m currently 5’9.5" (1.77 m) and this morning weighed in at 146.8 lbs (66.59 kg). I’ve lost 19 lbs since February and it’s almost all been fat. According to a recent Bod Pod measurement I am down to 5.8% BF and according to my Garmin Index scale on profile 7 I am at 8.4%.

The reason I ask is because a good friend pulled me aside the other day and expressed concern with how thin I have been getting. All of my clothes (pants with 30" waist) are hanging loosely off me around my chest and waist, my face has thinned, and my veins are more prominent. It’s done wonders for allowing me to have a 6-pack but now I wonder if I’ve gone a little too far.

If I start to add weight back on it’s probably going to be mostly in the form of fat again. Is this a problem? Would it be helpful to get back up towards 10% BF? It has been nice gaining free weight reductions on the climbs, but I wonder if there’s a chance I might be sacrificing endurance fat stores and “the look in the mirror”.

Others may know better but I’d be sceptical on both those BF measurements.

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I’m not taking the measurements as gospel. I think only a dexa could tell that. However, I have gotten my waist size down to 27" or less and I am noticeably “thinner” than most. I lift as well and haven’t noticed a lot of decreased strength or loss of FTP. So I do trust the tools that a majority of the lost weight has been in the form of fat. I just wonder if it’s something I should be cognizant of and try to level off or not concern myself if I let it start to climb back up.

Sounds like a perfect race weight! How much muscle mass do you have? Do you have the typical hardcore cyclist build?

I wouldn’t say hardcore. I still have a wide chest and shoulders with a 6 pack. I grew up playing baseball and football so there are residuals from that, and now do a lot of bodyweight and dumb bell weight lifting. The Garmin scale (again on profile 7) has the muscle mass at 66 lbs average for the past 4 weeks and the Bod Pod read close to the same.

I’m a little taller than you (181cm) and little lighter (65kg) and not had any direct comments. My scales say around 10% BF. Don’t really care about the absolute number, but I think your profile is pretty ok for cycling. Would not worry.

Your mate might have a point that at this profile you may look a little gaunt in the fact, but go on how you feel: feel tired? Strong? easy to wake up? easy to sleep? Good appetite? Then I would not worry. It is normal for endurance hobbyists to look a bit skinnier than average joe.


Good point. It might be that more and more people around seem to be getting heavier, especially as the season changes. I feel fine and my performance has only changed directly related to my commitment to the training plan. I think I heard in one of the podcasts that nearly all endurance athletes have enough body fat to rely on for longer events as stores. And many of those are far more thin than I am.

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I got down to 10% according to my Aria from 18%. I attracted similar interventions. I went back up a few not because of that but because I couldn’t handle the cold at all! :cold_face::cold_face::cold_face::cold_face::cold_face:

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Sorry if I ramble on here!

two things: you are spot on re fat reserves for performance, you can consider this as a near infinite source of energy, but most of us aren’t adapted to tap into those easily, and you can’t just go from carb to fat adapted in one fell swoop. However, you get fitter and you have better fat oxidation. Seems though your performance is all good which is important.

More importantly however is your health. I assume you aren’t pro so ignore all the crazy BS they do. My ex-girlfriend suffered from eating disorders and this is not to be taken lightly when having very low body fat - you aren’t anywhere near that but just a note from my experience do not focus too much on it, just eat healthy and you will lean out… Your hormones and related go completely out of whack. So, all in all, make sure you feel alright, eat macros well-balanced, eat when hungry, don’t go super high-carb unless your going to pummel a race, just eat balanced and when hungry, it works well to get to your lean state (at least for me).

Sorry for the side-tracked discussion. Now, where are the haribo…? ; )

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A few ways to look at this:

  • Are you getting sick frequently?
  • Are you eating enough to maintain adequate energy availability? (30*fat free mass in kg. For you, this is prob ~1800-1900kcal)
  • Has your performance or fatigue profile changed? (loss in performance, increase in fatigue)
  • Has your concentration or non-cycling life suffered? (job performance, etc)

If you answered “Yes” to any of the above questions, your body fat might be too low.


I’ll also add that getting properly fitting clothes will go a long way towards people not making comments about “being too skinny”.

I finally went out and got some properly fitting jeans and shirts for my size (finding 28/34 jeans was annoying) and the comments went from “you need to eat!” to “you look fantastic, your training must be going great”.


^ This. I was 4.75% body fat in my last bod pod measurement a few years ago. Measurements are prone to error, so best to go by how you feel.

The way the bod pod works is it measures your body volume. Then from a measurement of weight, your density is calculated. The algorithm then calculates your implied ratio of fat and all-else to solve for that density - which requires the algorithm to have set values of density for fat and all-else.

So there’s room for error in the bod pod measurement and calculation. Two measurements - weight and volume; and then two inputs - density of fat and density of all-else.

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Obviously it is subjective to the individual, but I thought id share my past body fat measurements. I am usually around 8% sometimes dropping lower then that and have never had any issues. I rarely get sick and to me this is just my natural body fat %…but being cold is something you’ll just have to get use to. The scans are taken using Bioelectrical impedance analysis. Hope this helps at all

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I have definitely noticed the cold and the shivers a lot more just sitting around the house!

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This is very good advice, thank you. I think it’s easy to stare at the numbers and start chasing metrics and develop a bit of an obsession. I think this friend was afraid of that because earlier in the year when I mentioned I was down over 10 pounds I said something along the lines “It’s free to get rid of weight on me versus buying a new bike!” Because they mentioned the other day that weight savings was good and all but not worth my health.

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This is also really good advice. I think wearing baggy clothes that look like they are hanging off me isn’t helping. It also doesn’t help that the season changed and now my bluejeans, sweaters, and shirts from last year all seem far loser than they did 12 months ago.

Also when I went back up my VO2 max resilience came up. No idea why as that’s carb driven if you follow the science. Wasn’t specifically working it but I wasn’t avoiding it either.

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Your friend might have just noticed that you were thinner than the you that he remembered.