Weight loss: 2 secs/lb/mile really accurate?

125 seconds vs. remaining fat and not working out at all, yeah

I'll throw myself under the bus here and offer a study with sample size of 1.

In early 2012, I ran halves in 1:26:20 and 1:28:10.

In late 2013, I ran halves in 1:39:00 and 1:39:50.

In early 2012 I weighed 194.

In late 2013 I weigh 215.

So I gained 21 pounds but lost very roughly 1 minute per mile. Now I have been running less, but even with the 1:26 I was under 40 mpw.

For those that just have excess fat, as I do, then I think there is some semblance of truth. I'd love to have an alter-g for a day and see what I could run right now if I was "194" again.

It is a not always accurate in every case. If you are lighter, you will be faster. Don't worry about the formula , get light and run fast.

It probably is more accurate as you get into the 2:40-3:00 range. I know after recovering from a cycling accident, I was around 6kg heavier than before. I went from 183cm and 66kg to 73kg. My half went from 1:14:30 to 1:17:30, despite big millage and solid training. My marathon went from 2:37 to 2:48.

Six months later, I was back down to round 67kg and ran a 1:13 flat in the half. The weight difference was HUGE for my training and racing. I fluctuate a lot of with salt and water, and can notice a big difference with 2-3kg extra after a glutenous night out. Even with lots of energy, my splits are just hard to hit.

I am pretty muscle-less, so any extra weight I carry around is just skinny guy flab, rarely muscle. Maybe it would be different if I was gaining or loosing muscle, but its just chub.

Why waste your time asking the questions when you can go lose the weight and find out for yourself

I'll offer a few of my personal sample points as well:

June 2009 - 1:20:57 HM - 170 lbs. (6:10/mi)

November 2009 - 1:15:33 HM - 160 lbs. (5:46/mi)

24s/mi over 10 lbs loss -> 2.4s/mi/lb

February 2010 - 1:14:22 HM - 160 lbs (5:42/mi)

December 2011 - 1:12:52 HM - 155 lbs (5:33/mi)

9s/mi over 5 lbs -> 1.8s/mi/lb

December 2011 - 1:12:52 HM - 155 lbs (5:33/mi)

August 2012 - 1:10:34 HM - 150 lbs (5:23/mi)

10s/mi over 5 lbs -> 2.0s/mi/lb

October 2013 - 1:14:00 HM - 160 lbs (5:39/mi) *(Adjusted for altitude, actual race was 76:39 @ 5000+ ft)

November 2013 - 1:10:45 HM - 152 lbs (5:23/mi)

16s/mi over 8 lbs -> 1.75/mi/lb

Goal for the next few months is to get my fata$$ down to my HS/college racing weight of 140.

I wonder if it is possible that the rule is just a false perception. I was six foot, 205 lbs four months ago, with a PR weight of 170. I found that the extra weight really hurt my ability to train at a high intensity, especially as I upped my mileage. Right now I am down to 182. I wasn't really able to handle any near-race-pace training until I got down to about 190. Now, since I can handle the intensity, the weight is coming off much faster. So in other words, being fast makes one lighter, as well as being lighter makes faster. If I had trained on an alter-g (or even just a treadmill), I probably would have adjusted twice as fast.

Last point should be 2s/lb as well. Duh

TheGarbageDisposal wrote:

I'll offer a few of my personal sample points as well:

June 2009 - 1:20:57 HM - 170 lbs. (6:10/mi)

November 2009 - 1:15:33 HM - 160 lbs. (5:46/mi)

24s/mi over 10 lbs loss -> 2.4s/mi/lb

February 2010 - 1:14:22 HM - 160 lbs (5:42/mi)

December 2011 - 1:12:52 HM - 155 lbs (5:33/mi)

9s/mi over 5 lbs -> 1.8s/mi/lb

December 2011 - 1:12:52 HM - 155 lbs (5:33/mi)

August 2012 - 1:10:34 HM - 150 lbs (5:23/mi)

10s/mi over 5 lbs -> 2.0s/mi/lb

October 2013 - 1:14:00 HM - 160 lbs (5:39/mi) *(Adjusted for altitude, actual race was 76:39 @ 5000+ ft)

November 2013 - 1:10:45 HM - 152 lbs (5:23/mi)

16s/mi over 8 lbs -> 1.75/mi/lb

Goal for the next few months is to get my fata$$ down to my HS/college racing weight of 140.

How tall are you?

Immortal Lobster wrote:

So ican improve 125 seconds on my 5k by losing 20 lbs but not working out at all

No, you will have to do some running also

The rule of thumb in the OP actually squares (roughly) with the results of one scientific study I read.

I actually wrote an article about exactly this topic for Runners Connect a while back.

http://runnersconnect.net/running-injury-prevention/excess-weight-and-running/

In that article, I looked at the results from a few studies on the effects of excess weight on performance. These results were:

1) 1.4% increased metabolic cost of running per 1% increase in weight

2) ~90-115m less distance covered over a 12min time trial per 5% excess weight

Extrapolating from number 2, we could say that an 18min 5k runner would take ~30 seconds more per 5% weight. This would be ~10sec per mile per 5%, or 2 seconds per mile per 1% body weight! Not bad, given the back-of-the-envelope calculations!

For most runners, this'd translate to more like 1.4-1.7 sec/mi/lb, but for heavier runners, 2 sec/mi/lb is not a bad estimate—with the caveats that this is based on a limited number of studies with only a few subjects covering artificial increases in weight and only using a 12min time trial.

In reality, you probably adapt a little better to weight gained gradually over time vs. wearing a weighted vest. Also recall that losing weight, especially when you are already fairly trim, necessitates losing some muscle strength too, so I don't recommend runners who are of healthy weights worry about "racing weight" or anything like that.

WhitePony wrote:

TheGarbageDisposal wrote:

...

Goal for the next few months is to get my fata$$ down to my HS/college racing weight of 140.

How tall are you?

My driver's license has said 5-9 since I was 18, but apparently I lost a quarter inch somewhere in the last few years.

Based on most charts I can probably get away with 130-135, but one step at a time.

I lost 10 lbs in a 3 week period due to some personal issues that left me with no appetite. I continued training at a decent level but not at my peak from an effort or mileage standpoint. Approximately 2-3 weeks after my weight bottomed out I made a gigantic jump in performance seemingly out of nowhere. For example, my per mile pace for a 10 mile training run dropped 25-30 seconds based on comparable effort. That fitness lasted for maybe two months until my body adapted back to its prior steady state weight given my normal training load and I was back to my crappy old training paces. This all happened later in life and well past my HS PR days where I was 25 lbs lighter than my later life steady state weight. Since then I've had periods where I've upped my mileage considerably and not reached that level I attained after the weight loss. I echo a comment earlier that weight loss is more effective than training in improving performance, to a point, if you're well above your ideal racing weight. That said, I think targeted weight loss from eating less (versus weight loss resulting from more activity) is harder than training more.

13.1 wrote:

Is the 2 seconds/lb/mile for weight loss relatively accurate? I ran a half in 1:30 on 40 easy miles a week, and I could stand to lose about 15 lbs (it's been a few years since college). Would this really result in a 30 second per mile improvement? Looking to run another at the beginning of April and hoping to lose a few pounds in the meantime.

Yes. It is accurate for me. See similar post:

It's a rule that works the other way too; you can have too much fat or not enough muscle. I would bet that for every pound of muscle below a certain point, you are losing 2 seconds per pound per mile in lost potential output. It has diminishing returns at some point, as more and more mass provides less and less output, but I think most amateur, college, and HS runners are well below that point.

The rule shouldn't be "lose weight to get 2 seconds per pound per mile." It should be "try to achieve equilibrium between mass and output in order to not lose 2 seconds per pound per mile."

Thanks for the thoughts everyone, and for the other link. Didn't see that one before. In my case, it's definitely 15 lbs of fat! And I agree that the rule is meant for people losing excess fat, not current trim runners who are already at their ideal body comp.

speaksmymind wrote:

Why waste your time asking the questions when you can go lose the weight and find out for yourself

Of course I will, but I was wondering what others' experiences were. I'll be training more for this half too, so in my case any improvement will not be solely attributable to weight loss and I was looking to try to better understand that part of the equation.

Has anyone done this study using an Alter-G to simulate different body weights? It should be pretty easy to do a controlled study this way.

I do find that each pound lost is a minute off of my marathon time, but I wonder if it's because I'm lighter or in better shape.

VO2 max equation has mass in the denominator.

So the easiest way to increase your VO2 max is to lose weight.

It's that simple.

TheGarbageDisposal wrote:

apparently I lost a quarter inch somewhere in the last few years.

The angry quarter inch...