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Medical Opinion: Why some cyclists have much lower body fat than others

Posted on: September 9th, 2017

medical opinion body fat cyclists

Body fat in cyclists: Pawel Poljanski showed these legs, stripped of all body fat, during the Tour de France. His online post went viral. But how do some riders have such low levels of body fat? And why is it that others don’t; despite training and racing as often and as hard?

 

Medical Opinion: Body fat levels in cyclists

 

By Dr Conor McGrane

When I watch the Grand Tours I, like many, am struck by how ripped the cyclists are.

A Tweet by Pawel Poljanski during the Tour de France showed just how little body fat modern cyclists carry.  His legs were so stripped of body fat his veins went viral online.

That said; pictures of the great Sean Kelly back in the day looked not too far off. Body fat in cyclists was a key focus even back then.

Over the years there have been many scientific studies on body composition in both athletes and non athletes.

One unusual study centred on the body fat levels in “Castrati”; those choirboys who were castrated before puberty to preserve their high pitched voices.

These showed that although they grew to normal heights, they had a higher fat level.

There is also nearly 2,000 years of evidence and experience breeding horses highlighting the importance of genetics.

Race horses are thoroughbreds with lean muscular bodies that are able to race fast. Shire horses are bigger and stronger but slow.

So how does this apply to athletes and, more specifically, cyclists?

There are a number of factors which affect body fat levels. Some we can change. Some we are born with.

It’s probably better to look at them under a number of headings.

Genetics play a big part, diet another and training is a huge factor.

And then there are hormones and drugs; some endogenous and others are exogenous – the letter meaning taken by the athlete rather than produced naturally in the body.

Genetics are, to a large extent, something we are simply born with.

Twin studies and family studies have shown that inherited traits affect our height, size and indeed lean body mass.

In twin studies, despite different environments growing up; genetics caused a similar size and shape.

Some studies of twins did show, however, that the genetic traits only had a partial effect; different diets and activity levels had a large impact.

So what about the effect of training on lean body mass?

Aerobic training is needed to improve maximal oxygen uptake. It leads to a relatively modest increase in lean muscle mass but a significant reduction in fat levels (in elite athletes).

Weight training leads to a large increase in muscle and indeed lean body mass and fat levels.

It varies from sport to sport and tailoring it to the demands of each sport needs careful planning.

It also requires close detail to diet. There are interesting studies into HIIT (high intensity interval training) both short term and long term.

This is usually compared to moderate intensity continuous training (MICT). There are mixed results and to be honest some confusing and contrasting results.

Short term HIIT seems to increase VO2 max and reduce waist circumference but not a significant effect on lean body mass.

Long term HIIT training though seems to improve VO2 max, waist circumference and body fat levels.

Due to the types of people in these studies, the results have to be taken with some scepticism. Even with research, the effects on athletes, especially elite ones in cycling, are not fully understood.

The bottom line is they need to be tailored to the individual and his or her goals.

Diet is another area which has a massive effect on body fat levels.

There is again inconsistent data on low carb diets and other commonly used diets.

Energy expenditure and intake needs to be carefully balanced and all the other factors tailored to the individual.

The main hormonal effects on body mass are growth hormone (GH), insulin and sex hormones (testosterone and oestrogen, for example).

These are produced naturally in all of us and how our body produces and reacts to them (affected by genetics to a large degree) affects both our lean muscle mass and body fat percentage.

Of these, growth hormone seems to have the biggest effect.

While these are produced naturally, they are also available and used as drugs.

These are banned in almost all cases, although there are exceptions. Some athletes, especially diabetics, get TUEs for insulin; for example.

Growth hormone seems to have been abused for decades. The track sprinter Ben Johnston was using it in the 1980’s.

And until recently there was no effective test for them. Sammy Sanchez has recently tested positive for growth hormones.

Athletic studies have shown that they improve sprint capacity and reduced fat percentages.

Researchers also noted that while they found these effects with relatively low doses, they think athletes abusing growth hormones probably use much higher levels than consumed during the study.

And the researchers believed the growth hormones may have even more effect that the research concluded.

Interestingly, some people respond to growth hormones more significantly than others. This is again due to genetics.

The effects of growth hormones seem to be lost soon after using stops.

Cyclists who abuse them would probably need to take it long term to keep the improvements.

It seems with this drug; once you start you can’t stop without losing its effects.

Beta agonists like clenbuterol (used commonly in some countries to bulk up cattle and livestock) are another illicit method of losing fat.

In a way that is not fully understood they increase lean muscle mass and reduce fat levels. Beta agonists are also used to treat asthma.

The most commonly used ones like Ventolin seem to have no effect as they are cleared rapidly from the body.

Alberto Contador served a ban for use of clenbuterol. It is thought to be used in unregulated supplements so care must be taken when using these.

Insulin is needed for treatment of type 1 diabetes; indeed it is a lifesaving and necessary treatment.

Some anecdotal evidence suggests it is abused by some as an anabolic agent.

Overall I found researching this a fascinating but really quite confusing topic.

For every paper that claimed one finding, there seems to be another saying the opposite.

That said there is a consensus on a number of matters when it comes to body fat levels.

Genetics seem to play the largest role. In some ways champions are born that way.

Some respond better to training and naturally have higher lean muscle mass and lower body fat levels.

Stimulating our natural hormones through training will, however, improve us all to a large degree. A good diet is also vital. Inheritance remains the biggest factor though.

Abuse of certain drugs like artificial growth hormone, clenbuterol and others will, however, also lower body fat levels.

Different people will respond much more than others and it seems that once started they need to keep abusing growth hormones; especially to maintain any improvement.

I have tried to give a summary of what I found about body fat when I went looking.

As with all elite sports though, those riders at the top of cycling are not often studied by researches exploring the issue of body fat. Or if they are, the research is not published.

Hopefully though, this helps readers understand how some cyclists have much lower fat levels and higher lean muscle than others.


Dr Conor McGrane is a cyclist and as well as running his own medical practice has worked with Cycling Ireland as a doctor. He writes here in a personal capacity.


 

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