Is w/kg a poorly understood cycling metric? Does this result in eating disorders?

Anecdotally, cutting weight (denominator) to improve W/kg ratio seems to be treated almost equally good as increasing the numerator (watts). However looking at cycling math websites, it seems more power (numerator) is much more important than weight loss in many cases. This ( in my opinion) is not emphasized enough, and may cause eating disorders in some cases?

Obviously lighter is faster, but more power is seems to mathematically be much more important.

On the flats:
A 200 lbs rider on 20lb bike only requires about 15 percent power to maintain the same 17MPH bike speed ( this assumes a same body shape for aero, which is an exaggeration admittedly). But the point is that on the flats, the extra mass just contributes to a bit more rolling resistance on the tires. The air resistance has a much greater impact on required watts.

On hills, obviously gravity kicks it a lot more, but not at a 1:1 ratio. At a 5% hill, maintaining 14.3MPH, our 100 lb lighter rider needs to put out 243 watts. Does the 200 lb rider need 486 watts?..nope ‘only’ 400 watts.

DISCLAIMER…Obviously high W/kg means your a fast rider, and likely excell at hill climbing. If you are a bulkier world tour rider, you’ll never win the mountain stages. But, I do feel this w/Kg math is misunderstood by some and might not always have the best health consequences for some people.

… Disclaimer… I am relative newbie to this cycling tracking stuff (I don’t track or follow my IF or TSS or whatever) but reading through post was a bit surprised this isn’t brought up more…or I could be out to lunch.

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Grand tours are won on the climbs, but with notable exceptions, most cyclists riding around their area never encounter a climb where W/kg really matters. Most often it is some sort of anaerobic repeat measure that helps them win a race or stomp their buddies up “climbs” of a couple minutes or less. This is a forum so you have state obvious stuff like “if taken to the extreme of a 275 lb rider vs a 145 lbs rider then obviously W/kg probably matters” but for the average cyclist it just isnt a relevant metric of performance. More watts is better even if it costs you a few extra lbs


Yes and yes.

And I’d agree that extra watts always help and that extra weight only hurts significantly in some situations. But w/kg and specifically weight is important to performance, particularly in the context of body composition. There is no benefit to carrying extra fat on your body and plenty of downside (both for cycling and general health and quality of life). If you are talking about losing muscle hoping to increase your w/kg, this is where things get trickier. It’s possible to lose muscle without losing power (particularly if it’s upper body muscle), but that’s where you get into trade offs between overall health and performance on the bike.

None of that really touches on the eating disorder point. Whether driven by cycling goals or other factors to lose weight, it’s always a risk when people try to lose weight for bad reasons or in an unhealthy and/or uneducated manner. I don’t think blaming w/KG is right, cyclists and runners have been obsessing over weight since people started racing each other (long before w/kg was in the discussion). I’d actually argue that weight (rider and equipment) has been less of a focus in cycling in the last 15 years that it was “back in the day”.


Compound score is the answer. It is a better predictor of one day racing success even at pro level, than W/kg.

Compound score squares the watts as they are more important. So for example:

Rider 1 is 60kg with 250W, whilst their w/kg is 4.17, their compound score is 1,042 W^2/kg.

Rider 2 is 80kg with 320W, their w/kg is 4.00 but their compound score is 1,280 W^2/kg.

Rider 2 is more likely to have more success in racing than Rider 1, even though Rider 1 has a higher W/kg.


The thing is that it is WAY easier to drop weight than increase absolute power, even if dropping weight stagnates progress on absolute power or even slightly lowers it.
You can drop 5lbs in a month, but it might take 6 months to gain 5 watts.


There is a pretty important function of carrying extra fat - it reassures your body that you aren’t dying. Very obviously that is somewhat hyperbolic, but if you are training, eating a reasonably well balanced diet (NOT frozen pizzas 5 times a day), your body is going to find a comp it is comfortable with. If you are sitting at 300 lb of course you probably need to find a lifestyle that reduces your body fat %. Can you tweak it in the short term for specific purposes? Sure but not in the long term. Many a dark place have been found by trying to “get lean” like the cyclists on TV or the lucky few who ride around town with spontaneously low body fat. I think they hit on this in the last podcast - the ability to tolerate or maintain that low body fat that most endurance athletes want has a very large genetic component. Doesn’t mean you can’t be healthy and be powerful, just means you might not look like MvdP doing it.

Why using W/kg and then talk about weight in lb?

Just use the SI on an international forum


I’m not talking about getting down to pro tour level BF% (which is often pushing into unhealthy levels), most of us amateurs have a bunch of fat to lose before we are even in the neighborhood of unhealthy or your body thinking it’s starving. Very few amateurs are anywhere near single digits and I’d bet most are above 20% (you can look very lean and still be over 20%). And I disagree that everyone can get to an ideal healthy body comp by eating a balanced diet. You can eat too much healthy food and extra fat from unhealthy food is no better than fat from the pizza. I’ve struggled with weight for a significant portion of my life and I know it’s a touchy subject, but I’m personally not a fan of the current trend of celebrating body types that are scientifically proven to be unhealthy and cause long term problems. Having a discussion about these things is not fat shaming or being mean, but for some reason that’s how it’s seen in some circles.


Well, 300 lbs is about 1334 N. But my sense is that no one really uses SI for their weight.

(Not intended as snark; just amusement about how even simple things often are not …)


Newtons are a measure of force, and pounds can be used as a measure of force.

However, the correct unit for mass is kilograms, and most of the planet does use kilos routinely to discuss their weight. (NB: the definition of weight is mass multiplied by the force of gravity, so as long as we’re on Earth, most people use mass and weight interchangeably.)

Converting from pounds to kilos is not hard. The conversion factor is 2.2, so take 10% off then cut it in half and you’ll be in the ballpark. 300 lbs minus 10% = 270. Half of that is 135 kg. The actual conversion would be 136.08kg, an error of just under 1% which is reasonable in daily life if you’re doing things in your head.

In the other direction, the math is easier and even more accurate. Take 136kg and double it to get 272 lbs. Add 27.2 to get 299.2lbs. The error is less than half a percent.


W/kg → eating disorder is just one facet of unhealthy obsession. Addiction can be developed from anything (lowest RHR, training volume, etc). It just takes certain personality. I have been guilty postponing family responsibilities to get some longer rides in every week :blush:


What svens said.
I might add that another misconception is that athletes, performing at the highest levels, are a role model for the highest level of health. This is often not the case. Regardless of the sport.


Yeah, what @svens said.

And what @KSwan said.

The highest levels of performance in ANY specific field are often not attained with the highest levels of health. And ANY metric can be a target for someone to fixate on. The addictive behavior is not dependent on how good, bad, popular, or unpopular the metric is.


Eating disorders are unfortunately common in every single endurance sport. Extra body mass (not just fat but unnecessary muscle) will always be detrimental to performance

I need to find the study, but someone looked at excess body fat (and a few other metrics) in Ironman athletes. From the pros to the age groupers, they were able to fairly accurately predict their finishing position purely based on how much excess they were carrying.

It’s simply easier to lose weight than increase power, especially when you’re getting to the pointy end

I don’t recall what studies he references, but “racing weight” by Matt Fitzgerald has some pretty good insight into this. Not so much on muscle mass, but the clear message is that lower body fat translates to better performance (amateur and pro). It’s a pretty good book with a very pragmatic view of weight and body comp in my opinion. Lot’s of practical suggestions to help move things in the right direction. I’m sure many of the discussions might be frowned on as contributing to an unhealthy focus on weight and body comp, so read with caution if that doesn’t sound like a safe place for you.


It’s not just that, but losing weight can actually improve power output through efficiency and economy. Less body mass means less weight your body has to support. Lowering pressure on your hands, feet, and a$$ reduces parasitic losses and increases your overall power output vs energy expenditure. Your ability to stand up or hold a tight aero position for longer goes up, which means less energy being spent that’s not propelling you forward. Lowered frontal area due to less body size, less frontal area due to the body position, less parastic losses of holding up more body weight, all equals less effort needed to go at a certain pace, and less fatigue by the end of a race, which equates to more ability to put down power when you need it. If you’re a crit racer, maybe it’s not a huge gain, but for long road races, even when it’s flat, losing excess body mass can be a real advantage.

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I agree, fantastic book! His book was what made me take my weight loss serious!

Under this topic, it sounds like putting out fire by pouring gasoline on it, though :slight_smile:

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Exactly what I find to be true. My highest FTP always aligns with when I’m at my leanest and lightest. To be fair, that’s also when I’m most serious about my training and nutrition, but my personal experience doesn’t align with folks who say they lose power when dropping weight. We are all different, but I’ve never seen a study or any science that shows a performance benefit of excess fat. Losing muscle is a lot more complex topic, but fat can be lost while maintaining or even increasing muscle mass and/or power. There is no downside to losing fat that I’ve seen until you get into levels that I suspect very few of us are close to.


Being at an optimal weight is undeniably very important to maximize performance in many sports, not just cycling. That’s why athletes worry about their weight. And that’s also a reason some of them develop eating disorders. In that regard, it’s a sometimes dangerous balancing act athletes have to play to be at their best.