Is this a load of nonsense?

Dropping weight to run faster?

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15/08/2012 at 00:40

Hi All

I have recently re commenced running with the rather ambitious target of doing a sub 40min 10K next May. In the last 9 weeks I have shaved 4 mins of my time - currently just over 50 mins. Hence, a heck of a lot still to do.

I have reasoned with myself that I should be able to get 10% fitter and hence, this should equate to 10% decrease in minute miles - say from 8.00 to say 7.20 - obvioulsy over time, not overnight.

My question is this -  say I drop 10% body weight, currently 12st - reduce to 11st. (I'm 5ft 8). Will the weight reduction of about 8% also mean I should be able to run on average 8% faster? Say knocking another 30 seconds from my average minute mile.

I am happy with my progress but just wondered what peoples thoughts were on this.   I realise that  reducing my weight means there is less effort required but does it work like that?



15/08/2012 at 07:43

i recently lost a stone for no more than vanity reasons if i'm honest.. i didnt get faster as a result, but i did notice my faster runs became noticibly easier, this may be a placebo but i suspect its not. 

15/08/2012 at 07:49

Try one of the calculators. Personally have no experience of them.


15/08/2012 at 07:57


yeah i have actually, in fact i set my PB in a 10k race recently, I'm sure the weight loss had something to do with it, but i think it was a small factor, i'd been training harder and rather than just training and running for fun, i actually dedicated some time to a specific 10k plan, so i dont want to say the weight did or did not make a difference, 

15/08/2012 at 08:03

The estimate is that for every lb in weight you lose you drop your 10k time by 10-12 seconds. From personal experience the estimate is about right.

In your example you could be reasonably confident that losing a stone would take 30 seconds a mile off your 10k time.

This assumes you need to lose the weight and that you are training correctly.


15/08/2012 at 08:05

If you really want to go quick, lose the weight, join a club (or get some mates together) and get those reps in.

seren nos    pirate
15/08/2012 at 08:16

as long as you have the weight to lose and lose it the right way then it will make a difference to the speed..............once again there can be no hard and fast rules becaause everyone is different........there will be a point though when even if you lose the weight and become faster it might not be healthy for you not a good idea to get obsessed with more weight lose will always mean lowwr times.......

but a stone for you should help with the speed..but you will not know how much of the gain is due to the better and more training you are doing and how much will be the weight............

good luck...

15/08/2012 at 09:31

Have a read at this:

Interesting stuff! Obviously not many people will have the strength of will (or even the desire) to become as lean as elite athletes, but it seems pretty certain that the less fat - and unnecessary muscle - you're carrying, the faster you will be able to run.



15/08/2012 at 09:38

When I first cracked 40min 10K I was around 11:3 (I came down from 12 stone over the previous 5-6 months). I'm not much taller than you at 5'9.

I can't comment on your maths, but doubt that there is a direct correlation between % weight loss and the same % increase in speed, but if you follow a sensible 10K plan and build up your weekly mileage to around 35-40 and drop the weight to around 11 stone, I think you'll be on for sub 40.


15/08/2012 at 09:43
12 stone does seem very heavy for someone so short. I think you need to get below 11 stone. I'm considerably taller and don't weigh anywhere near 12 stone.
15/08/2012 at 09:58
Also-ran wrote (see)

Try one of the calculators. Personally have no experience of them.


As this article points out, there is a direct correlation between weight and performance (that's simply physics) but with the caveat other things being equal - which they never are.  You can't just take the weight off like a weighted vest.  The good news is that if the weight comes off sensibly via healthy diet and exercise, you'll probably get fitter in the process, so your times should come down even more.

After I started getting seriously into running my weight seemed to settle around 12st (I'm 5'10'') so I thought this was a good weight and I was running some decent times off it (2:44 marathon, 1:15 half).  However, having I stepped up the training (and possibly tweaked the diet side as well), I've got down to 11st without too much difficulty and I'm running quicker.  It's impossible to know how much to put down purely to weight loss and how much is down to stronger running muscles/cardio fitness, etc. but it's certainly a big factor.

15/08/2012 at 13:13

thanks for all your input fellow runners

15/08/2012 at 13:29

Phil - 5'10"?? Thought you were smaller than that

11 stone? not bad going1 i''m 6'2" and the best I have got is 11.75 stones - don't think I get less than that!

15/08/2012 at 13:43

PH - I'm similar height and similar, but fluctuating weight, and can confirm ...

- the more I run, the less I weigh
- the more I run, the faster I get
- the less I weigh & the faster I get, the more I run ....

Until something breaks, then I eat and drink and start the cycle again.

15/08/2012 at 13:45
When people start saying you look ill because you are so thin you know you are in a good place. Usually people who get out of breath running up the stairs.
15/08/2012 at 13:58
Sussex Runner (NLR) wrote (see)
When people start saying you look ill because you are so thin you know you are in a good place. Usually people who get out of breath running up the stairs.

Conversely, when your aunt says you look a lot more healthy than last time she saw you, you know that the 3 month injury has taken its toll.

15/08/2012 at 14:01

hey im simon . im 15 and am currently running a 34 minute 10k. im 5f11 and weigh 10stone.Before I answer the entitled weighty question, I want to clearly support the idea that almost anyone can run and we don’t have to be preoccupied with weight or weight control to participate successfully in our sport. Age group runners come in every size and shape. One of the great things about cross-country and track in middle or high schools is that it is a no-cut sport. Everyone can participate. We even have the Clydesdale category in triathlons to recognize the bigger runners.

Ok, now to the question of whether weighing less can improve your running. The answer is a qualified yes.

VO2max (the maximum amount of oxygen you can process) is measured with body weight as part of the calculation. The more you weigh, the lower your VO2max and the lighter you are the higher your VO2max given the same conditioning. A higher VO2max is a good thing. Though it is not the best indicator of performance (it lags behind lactate threshold and vVO2max) a larger VO2max means you do have a larger “tank” to call upon. It is very likely in fact that a more efficient and powerful runner will out perform the runner with the higher VO2max.

So, though the lighter runner will have an advantage over the heavier similarly trained runner there is more to consider. How many of your competitors are trained just like you or you like them? Odds are there are wide variations in preparation. I introduce this consideration because you should address your overall training first in getting faster.

For the very reasons stated above, you want to become more efficient and powerful. You want a faster vVO2max (the minimal pace at which you reach your VO2max). All other paces are a percentage of this pace and so as you speed this up you drag all the other times with it. You also want to be able to process lactate superiorly. These things are accomplished by a comprehensive approach to your training which includes phases which move through getting you stronger (running specific strength), getting your basic speed faster and through race specific preparation. (By the way, notice that none of those phases include miles and miles of mindless “base” training.)

Here are my recommendations regarding weight loss and improving your running performance.

  1. If your body weight is already within normal ranges your goal should not be related to body weight. Start training appropriately instead.
  2. If your body weight is below normal ranges you should never consider weight reduction in your considerations for improvement. The adverse health considerations far out-weigh any effect on running (which will most likely be at best minimal and far more likely detrimental).
  3. If you are truly over-weight you may benefit from weight reduction. Your BMI (body Mass Index) or fat percentage are important numbers to take into consideration not just the number on the weight scale.

As part of a holistic and comprehensive approach to your running you should get a full evaluation of your diet. Do not under any circumstances get into any of the popular or fad diets and absolutely do not get into a low-carb diet. If you do not have an athletic diet, you will not have the energy available to do your workouts as prescribed. To workout, calories are required and carbohydrates are your staple. Therefore you will not be completing workouts at the right paces or completing the distances. If your workouts suffer, you don’t burn the number of calories you should and in the end will lose less weight instead of more.

There are two other points to make. High intensity workouts will have more effect on your metabolic rate (i.e. burn more calories even at rest). Increasing lean muscle burns more calories.

15/08/2012 at 14:37

Converting fat to muscle (by eating well, doing training and including the right amount of rest) is usually helpful. 

Converting fat to the sorts of muscles you are going to use to run (by eating what best suits you and your goals, run-specific training and including the right amount of rest) is even better. 

If you lose some weight while doing so, and (as several people before me have already stated) you remain heavy enough to maintain your long-term health, that's a bonus.

15/08/2012 at 14:40
Simon W. I just wonder if you could expand on that a little?
Tommygun2    pirate
15/08/2012 at 14:48

Wow sound advise from a 15yo

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