Intro: What is weight and height doping?
Weight doping in Zwift is where riders put in a lower weight on Zwift than they have in real life. This means their watts per kg (W/KG) will be artificially higher, which helps them to go faster, particularly on climbs. A quick google search will reveal how much discussion there is around weight doping and its impact on Zwift races.
There is also reverse weight doping. That involves putting in a higher weight so that you can race in a lower category without being flagged.
Height doping is where riders put in a lower height than real life. This can be done for two reasons – either to make their weight doping look less suspect or to reduce their air resistance in the game. Zwift’s air resistance takes into account rider size, so a taller rider will have higher resistance.
How much does weight and height doping happen?
We have set out to try and answer this question using data we have collected. When racing on Zwift you do sometimes see suspect metrics, although some of these will be genuine. You also get some truly elite athletes on Zwift who will have very low weight – so it’s important to not assume that anyone who is 6ft and under 70kgs is lying.
We are using anonymized Zwift rider data and comparing that to professional cyclist data. We have data on c.600 Zwift riders and top 100 professionals. If everything was true and accurate, we are expecting to find that professionals for their height should weight less than Zwift riders of the same height. Height distribution should be similar across professionals and higher ranked Zwift riders.
Chart 1: Zwift Height & Weight vs. Professional Height & Weight
Our first chart is just a simple comparison of weight and height across all the Zwifters and Professionals. The vertical axis weight and horizontal is height. The orange dots are Zwifters and blue dots are Professionals.
As expected, many Zwifters are heavier than the professional cyclists who are the same height. However, there are a material number of Zwifters who appear to be lighter than professionals of the same height. It appears to be around a half to a third or Zwift riders. Considering this is across all categories that is quite surprising – remember these are the top professionals in the world, dedicated to cycling and keep their weight extremely low.
Chart 2: Cat A Zwift Height & Weight vs. Professional Height & Weight
In this chart we look at the same data but only include Category A riders from Zwift. On average, the Zwift riders appears to be heavier for a given height (as expected). However, there are a number of heights where the Zwift riders are the lightest in that group. For example for the three riders that 171cm, the Zwift rider is lighter than the two professionals (Remco Evenepoel and Bryan Coquard). That’s just one instance, but the 176cm & 178cm categories have a similar pattern.
This doesn’t mean they have put in the wrong weight, however it does become suspicious when they are lighter than the top professionals in the world.
Chart 3: Average Weights by Height and % of Zwifters Below Professional Average (Cat A Only)
This table compares the average professional rider weight by height to the average Category A Zwift rider. We then look at what proportion of the Zwift riders weigh less than the professionals in that category.
Generally the average Zwift rider is heavier than the average professional, which matches what we expected to see. However, across the whole group 27% of the Zwift riders are lighter than the average professional in their high group. In other words, if you took a random Category A Zwift rider and compared them to a top professional of the same height, 1 in 4 times you would find that they are lighter. There is no way to tell (at least that we can think of) whether that is right, but it does seem high and would indicate that weight doping on Zwift is prevalent.
Chart 4: Height Distribution
This chart looks at the height distribution of Zwift Category A riders and the Professional riders. Based on this data, the average Zwift Category A rider is shorter than the Professional rider. 50% of professional riders are under 180cm compared with 60% of Zwift Category A riders.
As mentioned above, height doping on Zwift has two impacts – you create less drag (so go faster) and it helps weight doping by making a lower weight look more believable. So there is a concern that the average Zwift Cat A rider is noticeably shorter than the average professional. That said, this a relatively small sample of 100 professional riders and 140 Zwift Category A riders, so by no means conclusive.
It’s hard to say for certain whether anyone is weight and height doping on Zwift, however, the fact that many higher ranked Zwifters tend to be of comparable weight (or lighter) than Professionals, and that the average Zwifter is shorter than professionals does raise questions.
What proportion of Zwifters are doing it is hard to say, and to what extent is even harder. Is it commonplace to just shave off a couple of Kgs and a few centimetres? Or are there just a few riders who completely alter their physical stats? I’m not sure you can answer those questions with this data, but to us the results in these charts definitely look suspect.
We would like to note though that this is not a criticism of Zwift. We think a lot of this is probably some ‘minor’ weight doping – a few kgs or centimetres. That is pretty much impossible to spot, and short having an independent way to verify every rider’s weight we don’t know how to solve that.