Not long into The Rider, that enduring classic by Tim Krabbé, there is a little anecdote which neatly captures cycling's utter obsession with weight. In some ways it makes sense and in other ways it makes no sense at all.

Jacques Anquetil, the five-time winner of the Tour de France, used to take his water bottle out of its bike cage before every climb and stick it in the back pocket of his jersey. Ab Geldermans, his Dutch lieutenant, watched him do this for years, until finally he asked Anquetil why.

Steepest inclines

So Anquetil explained: a rider is made up of two parts – the person, and the bike. The bike, of course, is the instrument the person uses to go faster, but its weight also slows him down on the steepest inclines. His secret was to ensure the bike was as light as possible. One quick and simple way of doing this was to take the water bottle out its bike cage, transferring the weight to the rider. Makes sense?

Anyone who cycled over the Wicklow Gap this week – or any week, for that matter – should be able to relate to this. On the steepest inclines, especially with Storm Desmond approaching, it is indeed weight that is slowing you down. Only it shouldn’t matter if that weight is on you or the bike. It’s more about the engine that is driving it, and that is the person first, then the bike. Makes sense?

Either way this is the central argument made by Chris Froome in his latest attempt to dismiss allegations of doping during this year's Tour de France. In the UK wing of Esquire magazine, Froome is the subject of a 4,200-word feature entitled The Hardest Road – which hopes to answer once and for all how Froome managed to turn himself from a "chubby" domestique to a two-time Tour winner.

Simple conclusion

“The engine was there all along,” says Jeroen Swart. “He just lost the fat.” That’s actually how the feature ends, after Swart, a South African sports physician, analyses the data from tests carried out on Froome last August at the GlaxoSmithKline Human Performance Lab, in Brentford, west London. The simple conclusion is that Froome always had the blood profile and power output and oxygen capacity to win the Tour de France: he just needed to ease back on the Kerrygold and start using I Can’t Believe It’s Not Butter.

That's not me making fun of the data. There is certainly some validity in the idea that a massive loss in weight has contributed to Froome's success, although the way Esquire magazine present it, as if Froome has only now stumbled across this explanation, raises more questions than answers.

There is also the comparison data, from 2007, reportedly the last time Froome visited a laboratory for such testing. Anyway, according to Esquire, Froome was weighing in at a hefty 75.6kg back in 2007, with a body fat of 16.9 per cent. No wonder Swart describes him as "chubby", even though Froome was already a 22-year-old professional nearing the peak of his power.

Indeed just four years later, during the 2011 season, Froome is upstaging his Team Sky leader, Bradley Wiggins, by finishing second in the Vuelta a España. Froome won the Tour outright in 2013, and by the time he won it back this summer, was weighing in at 67kg, more than 8kg lighter than his previous racing weight.

As a direct result of this, he’d also increased his power-to-weight ratio by around 10 per cent, and his Vo2 max (the ability to absorb oxygen through the lungs) from 80.2 per cent to an estimated peak of 88.2. This could also account in part for Froome’s increase to just over six watts-per-kilo power output is this year’s race.

The problem with performance data such as this is that some people will always question its validity. When Vo2 tests first became a popular measure of physical effort, in the 1990s, Sean Kelly famously asked: “But do they measure suffering?”

Certainly impressive

Froome’s data is certainly impressive, although anyone who has experienced the unbearable lightness of being a professional cyclist – or in my case a distance runner – will understand that maintaining a similarly sustained power output after losing over 8kg in racing weight is not so easily done. So how did Froome do it?

Froome weight loss is contributed to the “marginal gains” which he and Team Sky frequently refer to.

Like, during this summer’s Tour, the “marginal gains” which contributed to Froome’s crushing ride up the La Pierre Saint Martin, on the second Tuesday of the race, to take charge of the Tour.

Or to his Team Sky escort to the finish on Plateau de Beille two days later, where, and despite riding into a headwind, both Froome and team mate Geraint Thomas eclipsed several of the previous fastest climbs up the 15.8km ascent, including Lance Armstrong’s best from 2002.

Indeed only last month, while attending the Web Summit in Dublin, Froome conducted a 20-minute interview on the very subject of these “marginal gains”, and reeled off several examples such as hand sanitiser (to help prevent infection), memory mattresses and pillows (for a better night’s sleep between stages) and stationary bikes (for an important cool down after those tough mountain-top finishes).

There was no mention of weight loss, or diet, or indeed doping. Later, his wife and manager, Michelle Froome, emailed me explaining that Froome had touched on doping in an earlier 20-minute interview, so why should he touch on it again in an interview about “marginal gains”? In some ways that makes sense and in other ways it makes no sense at all.