Body Composition: More Than A Figure On The Scales

Learn to track changes across different training cycles

Like many athletes, you may spend time checking the shape and changes to your body or the numbers on the bathroom scales.  But are you sure that your personal assessments are really helping you to improve your performance and management of your body composition?  Thankfully, science has an answer.  The scientific name (or names) for assessing athletic physique are Anthropometry and Kinathropometry, and there is a lot to learn from these disciplines even if you are not heading for the next Commonwealth games or Olympics.  Assessing physical characteristics can help us monitor changes in our bodies in response to training programs, describe our body shape, guide us to predict a safe amount of weight loss/gain and can track certain health data. 

In some sports like long-distance running, body mass must cover a great distance.  This means being ‘lean’ can be an advantage, so optimising body composition can give the athlete a competitive advantage.  On the other hand, regularly measuring body composition can also help us track whether a ‘desired weight’ is both healthy and realistic for the individual.  It can also help identify concerning factors like excessively low body fat mass which may become detrimental for an athlete’s health and performance.  

How does Body Composition Relate to Health?

Beyond sport, or for non-athletes, improving and tracking body composition, including lean muscle mass, can also help to improve general health.  For example, various studies have shown that having a greater lean mass may reduce the risk of developing metabolic syndrome, bone loss and age-related muscle loss problems such as strength, gait, risk of falls and tasks of daily living.*

Measuring Body Composition 

Enter the ISAK somatotype body composition profile: a rating of body shape that includes the three types endomorphy (adipose, or tending to store fat), mesomorphy (muscular) and ectomorphy (linear). See the image below.

Body composition somatotypes for sports nutrition

We measure the circumference of a number of different areas of the body, including bicep and calf. Over time, these measurements can be used to track changes in muscularity as part of the complete athlete profile and help to assess how effective a training or nutrition intervention has been.  These measurements are best taken at the beginning and end of strength training cycles or nutrition/dietary interventions to see the effectiveness of the training/diet.

 Skinfold testing for body composition

The skinfold thickness measures that are used routinely in elite team sports and athletes give us an idea of the amount of fat below the skin.  Usually, 8 skinfold measures are taken from the lower and upper body with the sum of these measures being used to track changes.  Weight, height, waist and hip measures are also taken to complete the profile and health data. 


What else should we consider with Body Composition?

When we look at body composition; remember that for some athletes the elite/ ideal skinfold may never be achieved, but by taking regular measures throughout the season and periods of training we can track the changes and progression in training, health and meeting a desired range for the race season. 

Clearly there will be individual differences in the rate of weight loss or reduction of the sum of the 8 skinfold measurements, but as a general rule, those athletes for whom the sum of their skinfolds (sum of 7 sites excluding iliac crest) is more than 80mm, a 1kg weight loss is equivalent to 10mm loss from the total skinfold, so pretty significant!

However, for those athletes with a skinfold total (sum of 7 sites excluding iliac crest) of less than 80mm, a 1kg weight loss is equivalent to just 5mm of fat loss across the body.  Of course there are many variables to the above and obviously body fat may be lost in other areas of the body which have not been measured! 

It is also important that skinfolds are monitored if they are too low.  For example, for competitive athletes a total of skinfolds (sum of 8 skinfolds) of 25-35mm (men) or 12-20mm (female) should be very closely monitored as this may mean a risk to health. 

Claire Fudge sports dietician measuring body composition on an athlete

When should we look at Body Composition and start making changes?

Body composition is something that WILL change throughout the year, across training cycles and across years.  But in general the most ideal periods to really work on optimising body composition are:

  1. During the off season: aim to avoid  more than +/-  2-3kg in weight 

  2. Ideally use the  preparation phase (up to 4-8 weeks out from the race specific phase) so that any adjustments to nutrition (matching/ not matching energy availability for short intentional purposes) to manipulate weight and body composition can take place before the very specific phase of training for racing

  3. If you plan to use more specialised metabolic nutrition techniques in training to manipulate physiological and metabolic adaptations, these need to be fully training cycles and excited appropriately with the support of a specialist sports dietitian or high performance nutritionist

Body Composition and The Off Season

One of the most common questions I get asked at this time of year is: “Should We Expect Our Body Composition To Change In Off-season?”

Absolutely!  Athletes can not be expected and should not expect to stay in “race ready” condition 365 days of the year.  We all need time during the off season when training schedules start to decrease in volume, intensity and specificity from race season and preparation phase. 

For some athletes who struggle maintaining weight during the peak of season this is a perfect time where they can ensure that they gain a little in stores to restock and remain healthy.

Try to keep your weight within +/- 2-3kg from preparation and race season, thereby making it easier to achieve your ultimate goal in body composition and weight.  Note we use both metrics not just defining it by weight here!

Nutrition during Off-Season

The off-season is a time to rejuvenate, refresh and find that spark for life and lust for training again; so we would also expect that athletes can relax a little with their nutrition.  I always think it is pretty stressful thinking about and planning food and nutrition all the time, however we have to accept that relaxing it will likely influence athletes’ body composition.

I encourage athletes to enjoy food; have a little of what you fancy without labelling it as good or bad.  In doing so one is more likely not then to over eat it!  That said, it might be off-season, but loosely following a guideline may be useful to ensure that we don’t eat in an “on and off” pattern  or encourage the yo-yo cycling of weight. 

Work with a qualified professional if you want to ensure you are getting accurate results!

Working with a qualified professional such a sports scientist or registered performance dietitian/nutritionist will help you to interpret your data, giving realistic and achievable body composition goals.  Of course, there is no point in having the data unless you know how to act upon it! 

So a dietitian will be able to advise you using the normative data from published values of athletes across a variety of sports as a guide to set your own weight/body composition goals. 

Interpretation of the body composition data is usually discussed and measured in terms of the total sum of skinfolds rather than a percentage, as this can be used to track changes over time and gives us a value to compare with ‘norm’ values.  So…..tracking different skinfolds gives us an idea of what is changing and where, rather than just a single percentage figure!  We also use your somatotype data and girth measures to help us interpret these results.

Essentially, ‘what is measured (and interpreted and acted upon!) is managed’!


*  Having a greater lean mass may reduce the risk of developing the metabolic syndrome (Park B et a 2013), bone loss (Ho-Pham L 2014) and problems associated with age-related muscle loss or sarcopenia (Lee J et all 2016; Wolf R 2006).