The belief of having one single ‘ideal’ body weight for racing is pervasive in endurance sport. Whilst perhaps founded in SOME logic, this belief is somewhat erroneous if not outright dangerous at times.
We break down weight, components and contributors to weight as well as discussing cutting weight for racing.
What is ‘Weight’?
Weight is the pull of gravity towards the centre of the Earth on your body, also known as body weight or scale weight. It has some correlation to body composition, but this is not a perfect one.
The body is composed of numerous components; bone, organs, muscles, fat, water etc. Generally people only really concern themselves with the muscle and fat components of the body as these two are the most malleable in the short term aside from hydration related changes. In this focus, the assumption from many people is that generally changes in scale weight are changes in fat, given the difficulty and incremental nature of adding muscle mass.
What can Impact Bodyweight?
The aforementioned changes to muscle mass and fat mass can of course change bodyweight. The skeleton itself can change in its contribution to weight, particularly if one has periods of non-weight bearing for example breaking a leg and not bearing any weight on it. Having a significant bone mineral density and thus heavier skeleton is crucial in long term health, aging and coincidentally this is also why exercise, particularly varieties with impact and strength training, are important (as the bone adapts to this load).
That said, fluid/hydration status is by far the most variable component of body mass. This is complicated to a degree by glycogen stores though. This is because glycogen is stored with water (each gram of glycogen is stored with 3g of water) so the two (glycogen and total body water) are somewhat tied together. Glycogen stores can be depleted via exercise and replenished via carbohydrate ingestion but the relationship between the two can make for a complex body weight situation. For example, replenishing 300g (10oz) glycogen, theoretically could change bodyweight by 1.2kg (2.5lbs). It should be noted that this relationship works both ways; body weight will decrease with glycogen depletion and increase with glycogen repletion (this is to ignore sweating and insensible losses in fluid status). Note, significant change in glycogen status is possible within a day of significant carbohydrate intake.
Faecal matter can play a role in body weight also, with riders in elite cycling teams reported avoiding fiber at times to help reduce their body weight. It bears worth noting here, this is a short term strategy, and the role of fiber in both health and bodyweight maintenance or body composition improvement is significant.
Of course, the impact of muscle and fat is real here too. These are not swift in their impact though and change over a much longer time frame (months). Whilst extra fat mass is rarely a goal outside of aquatic sports, increasing muscle mass is something many athletes are afraid of, likely without significant cause. That’s not to say that increased muscle mass is helpful (which it very well may be) but that it isn’t easy to acquire, particularly when in higher volume endurance training. Given the effort required for athletes who are actively training to gain muscle mass (contact sport athletes and bodybuilders for example) it should be fairly apparent to endurance athletes that things are not quite as linear as adding significant amounts of muscle mass from even moderate amounts of strength training in the context of significant endurance volume.
How Should You Track Bodyweight?
Just like glucose, many things can impact body weight, in both acute and more chronic timelines. So, just like glucose, you should be trying to limit the variables in measuring and understanding it. Similarly, you should consider the context for the measurement and what may be impacting it, this includes the menstrual cycle phase for women.
To limit the impact of nutrition and hydration, it is best to measure body weight in the morning, just after waking and using the bathroom. Ideally, measurements are done on the same day each week, if done weekly, or same day each month (e.g. first Monday of the month) if done monthly. That said, as with glucose, sporadic measures can be very difficult to discern. Some fitness professionals advocate daily weighing, then using averages over the month to limit the noise in the data set. Ideally a balance between data quality and obsession with measurement is struck and for those struggling with the scale, do not hesitate to seek professional help.
Whilst there is no specific answer to the best way to track body weight and this likely differs between individuals, the goal of this blog is to bring awareness and warning to the challenges around scales inferring body composition and a magic number on a scale being a gold standard for people.
As an example below is data from one of our staff members weighing themself almost every day for over 2 months:
As you can see from the dataset, there is significant day to day and week to week variation (500-600g which is 1.1-1.3lbs)
This is not to say to throw the scale out as much as to give pause to over-interpretation of the number it displays as a reflection of body composition.
If looking to evaluate body composition, the gold standard is a DEXA scan or underwater weighing (though this is very rare nowadays). This will give insight into percentages of body fat, muscle mass and bone mineral density amongst other things.
Surely Improving Power to Weight Ratio Improves Performance?
This would make sense in a simple system, which the body is not. The human body is a complex system, with any one change impacting a number of different factors.
For a fairly crude analogy of this belief, “lighter is faster”, may be akin to removing some of the nuts and bolts in your car. Whilst the car is now lighter, it may be less efficient due to the engine now having a small amount of movement inside the chassis.
A recent study looked into a short term (9 day) strategy of caloric deficit to elicit a body weight change in preparation for competition in elite race walkers. In the intervention group they managed to lose 2kg (4.4lbs), 1.6kg (3.52lbs) of which was fat, with a small loss in the control group of 0.9kg of fat (2lbs). Note, these were elite race walkers, and this is roughly 2-3% of total bodyweight lost given reported subject characteristics. Crucially the weight loss intervention group saw no improved performance when compared to the control group AND had an increased RPE (rating of perceived exertion) in comparison to the control group. Both improved by ~4% from the testing prior to the intervention (which was also prior to a training camp).
It is worth noting that both groups underwent a 24 hour carbohydrate loading protocol pre race and saw a body weight increase of around 300g as a result.
To quote the researchers; “the relationship between BM, training quality and performance in weight-dependent endurance sports is complex”
*note BM denotes body mass
The overlay on top of this is injury risk associated with low energy availability (LEA), which is of concern, specifically because as people often say “the best ability is availability”. LEA itself can of course lead to RED-S (relative energy deficiency in sport) which has its own significant consequence. We have discussed underfueling and associated risks previously in this blog. Performance is about more than just mechanics and physics, there is a huge role of psychology in this and thus treating the body like a machine without thoughts and emotions is fraught with risk.
Take Home Message
The interaction of body weight and performance is less linear than most appreciate and being well fueled, happy and able to sustain training is the most important factor in success.
If an athlete wants to improve body composition, because they have evidence that this is needed, or wish to do so for health reasons, then the strategy should be more long term and progressive over time. Those looking to improve body composition should also consider discussing this with a professional.
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