Coaching editor Phil Mosley investigates whether your New Year’s resolution to lose weight will really help come summer

Losing weight for triathlonHave you ever wondered what difference a few extra pounds in body weight might make to your triathlon race performances? Do those sneaky chocolates or glasses of wine really make that much difference? After all, Bradley Wiggins put much of his tour success to shedding weight, saying: “Compared to the 2007 Tour, my weight loss means I’m carrying the equivalent of six bags of sugar less up a mountain.”

So the question is, do triathletes stand to gain as much by losing a few pounds as cyclists like Wiggins do? We wanted to know, and so with the help of a GPS watch, a heavy backpack, and plenty of hard graft we set out to conduct a series of simple experiments, powering up hills and along flats while carrying an extra 3kg of weight. We didn’t know what to expect, but in the end the results really made us sit up and take notice, and we think you’ll feel the same.

1 Running Uphill

The first experiment was to measure the effect of extra body weight on uphill running. So strapping on two hydration packs,weighing a total of half-a-stone, I began the day’s testing. A long steady climb sprawled out before me, where a road sign warned of the 6% gradient. I anxiously toed the start line under dark skies, as the heavens began to open and the full length of the hill dawned on me. Starting the stopwatch I ran full pelt up the hill as if my life depended on it, while shouts of encouragement from the Triathlon Plus photographer grew ever-distant.

A few minutes later my Garmin GPS watch beeped to signal the end of the kilometre and I hit the cold pavement on all fours, gasping for air and asking myself why I had agreed to be the guinea pig for this stupid test. And that’s when I remembered I had to do it again. So I jogged back down slowly, took a drink, and when I’d had a 10-minute rest I began the arduous test again, but this time with no heavy hydration packs to weigh me down. “GO!” shouted the photographer and I sped off once more, up the seemingly endless hill.

Without the heavy 3kg backpack it felt totally different – like a bear had jumped off my back. I knew straight away that I would be quicker, and a few minutes later I was proved right. I had covered the measured kilometer a whole 14 seconds faster as a result of the 3kg weight loss.

So for me, I saved 14 seconds on an uphill run, but for you it could be more. I weigh 74kg and run a 10km in about 33 minutes. If you weigh more, or run slower, your 3kg weight loss could potentially save you far more than 14 seconds per km.

RESULT Running uphill, time saved:14 secs per km

Losing weight for triathlon2 Running on a flat course

Having already seen that 3kg of extra weight makes a big difference to uphill running speed, we went to a running track for thenext experiment, to see what difference that extra weight would make when running on flat terrain. So again my legs carried me as fast as they would go for a kilometre, but this time removing the 3kg backpack didn’t prove such an advantage. In fact the time difference caused by the additional weight was just five seconds per kilometer. But then I added it up and realised that over 10km race it makes 50 seconds difference, so maybe it’s not to be sniffed at. And again, the slower or heavier you are, the greater the difference that weight loss will make to you.

RESULT Running on flat terrain, time saved: 5 secs per km

It was starting to dawn on me that my diet needed to improve if I wanted to be a faster runner, but what about my cycling? The next day I decided to climb into my padded lycra shorts and find out.

Losing weight for triathlon3 Cycling uphill

Day two; another rain storm and yet another long 6% gradient to battle up in the name of science and journalism. Yet again I strapped on my trusty hydration pack, this time using standard bike water bottles for the rest of the 3kg weight. To maintain consistency between tests I stayed seated throughout the climb that cruelly seemed to get steeper the longer it went on. With hands gripping tightly on the brake hoods I took off in a light gear, imagining myself at Ironman Switzerland, pedaling as hard as I could go. When I reached the summit, I stopped the clock and turned back down the hill to repeat the test all over again, this time without the extra weight. After a couple more repeats to make sure the results were consistent I slumped down in the back of the photographer’s Land Rover, guzzled a recovery shake and took stock of the new data. This time the 3kg of additional weight had slowed me down by 13 seconds, a similar result to the hill-running test, and another significant potential time-saving. Again, the evidence was suggesting that I’d need to cut out my regular weekend Belgian buns.

RESULT Cycling uphill, time saved: 13 secs per km

However, there was one test that I was most interested in – one that could perhaps reduce the need for dieting. The flat terrain cycling test.

4 Cycling on the flatLosing weight for triathlon

This was more like it. No more hills to contend with and even the rain had temporarily abated. On a flat cycle path that used to be a railway line, I sat glued to the saddle as I thundered along, desperately hoping that I could ride just as fast on a 0% gradient, with or without my 3kg of bike bottles and hydration packs, my diet hanging in the balance. Several tests later, it was off to the pub to digest the results, feeling conspicuous for wearing Lycra in a public place. We decided to review the results before ordering lunch, in case it made a difference to our menu choice. The result? The extra weight only made me half a second slower over the flat kilometer cycle time trial. So we were left to conclude that a few extra kilos makes very little difference when riding hard on the flat. And with that in mind I decided to order the homemade cheeseburger and curly fries, safe in the knowledge that I could at least enter some really flat triathlons this summer.

RESULT Cycling on flat terrain, time saved: 0.5 secs per km


It was clear from our tests that body weight, or at least body composition, makes a big difference to triathlon performance. Take a fairly flat race like London Triathlon for example. Based loosely on our tests (and we accept that they’re not 100% scientific) a triathlete could stand to improve their race time by at least one minute, probably more, by losing 3kg in bodyweight. Add in some hills and the time savings start becoming much greater. And the heavier or slower you are, the more time you stand to gain from shaving a few pounds off your waistline.

However, a word of warning; losing weight can sometimes reduce your muscle mass or take you below your healthy weight. In this case, you won’t see any improvements, and you could end up getting ill. Alternatively, you may decide that as a triathlete you’re already fitter than most, and not worry about going on a diet. We all love triathlon, but for some of us there’s more to life than a few seconds saved in a race. Butterscotch Angel Delight, for example…

You can find more winter triathlon training articles here