Are Fat Mass and Fitness Levels Related?

Are Fat Mass and Fitness Levels Related?

Can You Be Fat & Fit?

LAST UPDATED: November 2018.

Author: Ben graduated from university with a Bachelor degree in 2005. He has played rugby for many years and is now a soldier in the Army Reserve.

This site was established to provide a free resource and conversational piece for readers looking to improve their performance.

We take a look to see whether total body fat mass has an effect on aerobic capacity.

What is fitness?

One simple way to describe fitness is the bodies ability to recover after a bout of exercise.

Therefore, if you have just run 100 meters and then performed 10 burpees at your maximum effort, your level of fitness can be assessed by the time your body can recover enough for your two perform the exercises again.

However, many people associate a muscular, lean body as being ‘fit’.

A toned and sculpted body shows that you do plenty of exercise and eat correctly to increase muscular size and reduce fat levels.

Yet, you will see many professional athletes, some Olympians or even soldiers that do plenty of exercise but do not have chiseled abs or big biceps.

When we see people with lots fat mass the consensus is that they must be unfit.

So this begs the question whether fat mass and fitness are related?

Fat mass, fitness and abs

It is very easy to mix up good health, fitness and fat.

However, consider this.

A study by the University of Chester, UK, revealed the average speed, distance and time spent on playing field per game for professional rugby union players.

The data was collected from players of eight top professional rugby union teams which play in the Aviva Premiership rugby annual competition and offered an insight in to the demands of a player.

The ‘forwards’ tend to be the bigger players, or traditional so. Now, in the professional era the players are generally much bigger overall and position by size is much more blurred.

However, during a game of 80 minutes split in to  two halves of 40 minutes the average distance covered by a ‘forward’ position player is 4.45km who would then run a maximum sprint pace of 23.7 km/h.


The game of rugby has very few break down of play, so the movement is fairly continuous and requires a high level of aerobic fitness.

Another, example of fitness without abs is the fitness legend that is Paddy Doyle.
Far from becoming any self proclaimed Instagram fitness model or offering ill considered and unqualified fitness advice across social media feeds, Paddy has accumulated a number of fitness related awards that has given him the title of the World’s Fittest Man by the Guinness Book of Records.
Paddy’s first awards started to trickle in when he joined the Parachute Regiment of the British Army whereby he was recognized as a champion recruit for outstanding fitness levels and determination.
This initial recognition was the catalyst for a lifetime of achievement of an endurance athlete.
However, if you were to put him side by side with Ryan Terry who is an international fitness icon and IFBB Pro Men’s Physique champion, you would think, as most others would, that Ryan is the ‘fitter’ of the two. 
However, there is certainly a difference between looking fit and actually being fit…


With these aspects in mind, there has a been a study put in place that wanted to establish the relationship between body fat mass and body composition with levels of aerobic fitness.

In essence, is a person who is considered ‘fat’ less fit than a person that does not have a such a high percentage of fat mass.

Are the examples we have previously discussed merely extraordinary, or does the study eradicate the mindset that fat people are not as fit as thinner people?

The aim of the study set out was to examine how much influence body mass has on the VO2 max.

One study involved 129 children participants who had a wide spectrum of body types and composition.

A second study involved 31 women and their fitness levels while they were overweight and then again after significant weight loss.

What’s VO2 MAX?

VO2 Max is the maximum or optimum rate at which the heart, lungs, and muscles can effectively use oxygen during exercise, used as a way of measuring a person’s individual aerobic capacity.

How did they perform the study?

To see how well the participants’ bodies could effectively use oxygen during bouts of exercise they were subject to a treadmill test

Their body composition was assessed using dual energy X-ray absorptiometry and a four-compartment model.

 What was discovered?

The results of the test demonstrate that free fat mass is strongly related to VO2max in that fat mass does not have any effect on VO2max.

Obesity in terms of Fat% is a better parameter than BMI for prediction of low VO2max.

This means, in general, those people who are fatter or who maintain a higher percentage of body fat are not able to effectively process are much oxygen.

Fatness and excess body weight do not necessarily imply a reduced ability to maximally consume oxygen, but excess fatness does have a detrimental effect on submaximal aerobic capacity.

With this in mind, this does then back the examples that are found in professional sport and contradict the notion and widely accepted though process that those who have lower levels of body fat are ‘fitter’.

‘Fitness’ icons or models are not a true representation of fitness levels and are merely a representation of aesthetic changes via a process of calorie control and muscle building which is different to aerobic capacity and aerobic recovery.

[Total body fat does not influence maximal aerobic capacity. Goran M, Fields DA, Hunter GR, Herd SL, Weinsier RL. Int J Obes Relat Metab Disord. 2000 Jul;24(7):841-8.]


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Ben BA(Hons), PGCert

Ben established this site to be a free resource in 2015. Since then it has gained over half a million visits. He has always been interested in sport and he started playing rugby at the age of 6 represented his town, county and school. Ben also enjoys cycling, has started skiing and is in the Army Reserve representing his Regiment as part of the 150 Regimental Shooting Team. He holds a bachelor's and postgraduate degree in sport exercise & nutrition.

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