Fat and fiction

Cyclists obsess over body fat – and it’s not just an affliction of the pros. But is less body fat always better, and how low is too low? Cyclist investigates the weighty matter of body composition

Bradley Wiggins and Chris Froome have won races in an extreme state, in terms of their body composition,’ says ABCC senior coach Ian Goodhew. He’s referring to the ultra-lithe appearance of the last two Tour winners, and questions whether amateur cyclists should emulate them. ‘It’s like girls looking at photos of stick-thin models and saying, “I want to be like that,” only Wiggins and Froome haven’t been airbrushed.’

The appeal of reducing body fat is obvious – for optimum performance you want the greatest power-to-weight ratio, and reducing the weight side of the equation will raise that critical figure. On top of this, excess fat can have a negative effect on your body’s ability to process oxygen, slowing you further, so there are definite grounds to support the concept of shedding fat to increase cycling prowess.

But it’s not simply enough to say, ‘I’m going to lose weight.’ It may be tempting to jump on the scales to find out your weight and perhaps calculate your body mass index (BMI). But neither of these figures will give you any useful clues about your body composition, ie how much of your total weight is made up of fat, muscle or water.

The number you really need as a starting point is your body fat percentage – quite simply, the proportion of your total body weight that’s made up of fat. It’s this figure that grabs the headlines when pros such as Wiggins are reported to drop as low as 4% in their pursuit of mountain-slaying speed. How this can be applied by non-pros is an area of contention however, because reducing body fat to extremely low levels can have implications when it comes to sustainable performance, overall health and mood.

The big issue

‘There’s an adage that lighter is faster, and to some extent it’s very true,’ says Greg Whyte, professor of applied sport and exercise science at Liverpool John Moores University. ‘Fat is non-functioning and non-locomotive, so it’s not generally helpful for performance.’

In other words, body fat is an issue for cyclists quite simply because it slows you down, especially when going uphill. ‘You can get away with carrying a little more body fat if you’re time-trialling on a flat course,’ says John Kelly, senior lecturer in exercise physiology at the University of Chichester. ‘As soon as the hills start, however, you’re battling gravity. The lighter the rider, the faster they go for a given effort. It’s also worth mentioning acceleration. Like going uphill, to achieve a rapid acceleration requires high power output against a light resistance. So low body fat is useful in this respect too. Data from elite athletes supports this.’


There’s good news from Goodhew. ‘If you train regularly, your VO2 max [essentially your aerobic performance] probably won’t be affected by your body fat, assuming you’re not 20 stone. Small percentage changes in body fat have only a tiny effect on VO2 max.’

But there is still the issue of excess weight in the form of fat slowing you down. ‘Clearly, weight is a critical factor in high-level performance, or there would be no drive to produce very lightweight frames and components,’ Kelly points out.

The right balance

Before you go on a crash diet, forget everything you thought you knew about
the pros. ‘There’s no such thing as body fat of 3%,’ says Whyte. ‘It’s an impossibility.’

Plus, body fat plays an essential role. As well as providing energy (it actually contains almost twice as much energy as carbohydrate), it insulates the body, forms structural material for cells, improves the absorption of vitamins in the gut, protects organs and helps transmit nerve impulses. This multitude of roles means you don’t want to lose too much, and helps to explain why everyone’s ‘healthy’ fat level is different.

So what is a ‘good’ body fat percentage? ‘A healthy range for a non-athlete is 20-25% for men and 25-30% for women,’ Whyte says. ‘Sportspeople tend to have less body fat, but the lower limit of function is around 10-15% for men and 15-20% for women. Any less than that and you’re susceptible to illness.’

This seems to be a figure the experts agree on. ‘Body fat can be as low as 6%, but this is very low and leaves little in reserve,’ says Kelly. ‘Most weekend warriors will be able to sustain 10% and be quite comfortable’.

Yet that doesn’t mean hitting 10%, 6% or some unattainable target you think the pros are capable of is something you should be hung up about. ‘Grand Tours are different to the real world,’ says Dan Lloyd, presenter for the Global Cycling Network and former pro. ‘How many sportives feature the same amount of climbing as the pros do in the Tour de France? None, so an amateur shouldn’t have the same attitude to body fat as a pro.’


There are various ways of determining your body fat (see below), but as a starting point to achieving your potential on the bike, which is what really matters, you need to consider your weight. The 10% body fat benchmark is a rough guide only and everyone’s ideal ‘racing weight’ is different.

‘There are two weights of interest: minimum weight and optimum weight,’ says Goodhew. ‘They’re slightly different. If you’re trying to get fit, you’re likely to reach a point where you can’t lose any more weight. But the optimum is often slightly higher because at your minimum weight you’re likely to have lost power. There’s a point, and it’s different for all of us, where we give up power at a faster rate than we lose weight. Your optimum weight will be the one at which you can maintain your maximum average power output per kilo.’

That optimum weight is likely to coincide with your optimum body fat percentage, which may be higher than the minimum you can achieve. Whyte agrees: ‘Power per kilo is vital, and there’s a tipping point for everyone where low body fat affects the balance between performance and health. You have an attainable level of fat mass that doesn’t affect health or performance, but you have to find it for yourself.’

Up and down

Once you’ve established this, the good news is that you don’t have to obsess about staying right at your racing weight. Not even the pros do that. ‘Pro cyclists get most of their media coverage when they’re in prime condition, race ready, pared down, with low levels of body fat,’ says Kelly. ‘This is unsustainable, as very low levels of body fat are difficult to maintain. Elite cyclists will “cycle” their weight throughout the year. Some individuals will struggle to maintain a racing weight. For instance, Jan Ullrich often looked pretty hefty in the off-season but he would trim down when it mattered.’

In fact, storing slightly more weight can be an advantage. ‘Training is seasonal,’ says Whyte. ‘In winter, if you’re riding long distances to keep your base fitness high, or doing a lot of work on a turbo trainer, a little extra fat can be a valuable energy source.’


Lloyd goes one step further. ‘I’ve seen amateurs who are so lean you wonder why they haven’t won the Tour five times,’ he says. ‘Then there are pros I’ve sat behind who have carried a bit of extra fat. Being lean doesn’t make you a good rider.’

Goodhew concurs that body fat is only part of the performance story. ‘Your body fat won’t change what’s between your ears,’ he adds. ‘Who can suffer the most? Does fat come into it? Take last year’s Giro d’Italia. Wiggins fared badly, but was that anything to do with his weight?’ Wiggins was reported to be heavier than usual due to his World Championships perparations. ‘Your postman could have overtaken him on the downhill sections, but was that the weather? Tyres? Illness? Was he nervous? It probably wasn’t anything to do with his weight.’

That said, getting lean provides definite advantages if you do it sensibly. ‘Body fat may be manipulated in one of three ways,’ says Kelly. ‘Diet, exercise or, in most cases, a combination of the two. If you’re looking to lose weight – ie body fat – it’s best done by a small, steady and sustainable decrease in energy intake, provided your energy expenditure stays the same. Do it slowly, perhaps only 300-500g per week. This is the equivalent of 3,500 calories going from your diet per week.’ Trying to rush things with crash low-calorie diets is likely to lead to the weight piling back on soon after it is lost.

Control yourself

It’s important to take a sensible approach, rather than simply copying what the pros do. ‘My former team-mate at Cervélo, the late Xavier Tondo, didn’t eat very much at all in the morning,’ says Lloyd. ‘He’d then have a slightly larger lunch after training, and then a slightly bigger dinner again. You have to find what works for you.’

How you ride comes into it too. ‘If you ride regularly for less than two hours you’re not going to burn much fat,’ says Goodhew. ‘Broadly speaking, after two hours your body switches from using glycogen, which is readily available, to burning fat. It may vary depending on your intensity or the terrain, but that’s generally true. So if a rider asks how to burn fat, I’d say ride for three hours.’

Power out

One thing all of our experts agree on is that, actually, your power-to-weight ratio is more important than your body fat percentage. ‘Power-to-weight is the most important predictor of performance,’ says Kelly.

And before you start obsessing about the weight factor, consider the dangers of getting too lean. ‘There was a guy local to me who lost so much weight he looked as if he had an eating disorder and was wasting away,’ says Lloyd. ‘I’ve not seen that happen to the pros but the danger is there for them just as it is for a club rider.’ The dangers he’s talking about are illness due to weakened immunity, reduced power output and power-to-weight ratio, bonking on rides through lack of fuel, general tiredness, lack of motivation and, potentially, depression. Some have blamed Froome’s famous bonk on Alpe d’Huez in 2013 on his minuscule levels of body fat.

‘We have to be careful about what’s practical for you versus what’s practical for a pro rider with a budget of millions and doctors and nutritionists around him,’ says Goodhew. ‘Chris Froome is an extreme example, and if you took him away from the bike a doctor would probably tell you he’s anorexic. His lifestyle is not something those of us with normal lives could deal with.’

Returning to Goodhew’s original analogy, it’s important you don’t look at the likes of Froome and think, ‘I have to be like that.’

‘As a coach, I have to remember I’m dealing with actual people,’ he adds. ‘Information won’t win you races, but it’s a tool, like having aero wheels or the best bike. Not all science is helpful to all situations.’

Understanding how your weight affects your speed is useful, and knowing your level of body fat is useful, but determining the optimum weight and fat ratio for you comes down to your lifestyle, what type of riding you do and your natural body make-up. You can only get to that by understanding your body and finding what works for you.

How to measure your fat


What is it? Measures body fat by pinching it.

How does it work? Special callipers measure skin folds at specified sites on the body. The readings, via complicated maths involving weight and age, can be used to calculate your body fat percentage.

How accurate is it? Reasonably, although there is a but… ‘There are hidden complexities,’ says Whyte. ‘Accuracy depends on the operator – there will be a degree of observer error – and the number of skinfold sites used. But it can be useful for measuring fat mass over time, as it will show a trend in weight changes.’

Body fat monitor

What is it? A fancy set of bathroom scales that claim to calculate your body fat percentage.

How does it work? The scales send a tiny electrical current through the body to evaluate its composition based on how different types of tissue impede the current. All you have to do is stand on them and wait for a reading.

How accurate is it? ‘It starts with “b” and ends in “ollocks”,’ says Goodhew. ‘It’s like saying your maximum heart rate is 220 minus your age. It’s OK if you don’t need accurate information, but don’t base a training or nutrition plan around the results.’

Hydrostatic testing

What is it? Put simply, a pool with scales in it.

How does it work? You’re weighed on normal scales first, then on a submerged seat in a pool of water having expelled as much air from your lungs as possible. By analysing your ‘dry land’ weight and your pool weight it’s possible to calculate your body composition due to the differences in buoyancy
of fat, muscle and water.

How accurate is it? Not perfect, but more accurate than scales. ‘This technique tends to only be available to laboratories though,’ says Kelly. ‘It’s expensive and you can’t do it yourself.’


What is it? Rather than using physical measurements, your
body is scanned.

How does it work? There are various ways of scanning a cross-section of the body (such as CAT or MRI scans). Computer programmes can then measure body fat (plus muscle, bone and tissue)
in the image, and project
it throughout the body.

How accurate is it? Very, but the high cost isn’t the only drawback. ‘They also require significant operator training, a lot of space, and are time consuming,’ says Kelly. Goodhew suggests helping in a trial at your local university.


What is it? Dual x-ray absorptiometry is a step up from MRI scanning.

How does it work? You lie in a machine that uses two x-rays with different energy levels to take readings from your body. It can be used to measure bone density, lean soft tissue and body cell mass.

How accurate is it? ‘Very accurate,’ says Whyte. ‘It measures whole body content rather than only measuring one portion. Because it’s an x-ray there’s a limit on the number of times you can use it.’ As with MRI scans, DEXA testing is most commonly available at universities and labs.