The impact of losing weight on your running

Does losing weight impact your running?  How much?  How?

Clearly, common sense and Newtonian physics would say that losing weight make you faster.  And it does.  But there’s probably more to the story than that.

Has this ever been tested?

Yes, it has.

The first test in the 70’s used a methodology where they put a harness on people and tested how fast they could run 2 miles.  Over a series of iterations they added weight to the harness.

And, as you would expect, the more weight the slower the pace.  How much slower? It turns out a pound is worth somewhere between 1 and 2 seconds per mile.

But I have a number of questions.  Where these actual ‘runners’ or random grad students?  Why 2 miles?  What happens if you make it 10 miles, or 26.2 miles?  How does it correlate to heart rate and perceived effort?

There was a newer study where instead of adding weight, they used a harness, like one of those AlterG treadmills, to remove weight.  In this case they had runners do a 3K race trial.  For each iteration they took weight off.

And the result was a pound was worth 2.4 seconds per mile.

But, beyond the basic, obvious, less weight equals faster pace, I’m still curious how this relates to longer distances and how it correlates to effort.

According to these tests the 25 pounds I lost over the summer is equal to around 25 seconds per mile.  Or let’s say a minute and a half faster for my next 5K.

That feels about right.  I can live with that.

But, I think it is also a fairly minimalist and myopic set of assumptions and conclusions.

In my experience the weight loss has more impact than the stated 1-2 seconds per pound.

It also impacts your training.  It makes it easier to train.  It makes the training runs more enjoyable, which in turn makes it more likely you will do them.  It’s a positive feedback loop.

When I was younger, I told myself that it was better to start heavier and then run the weight off as I trained.  That way I would benefit from the ‘bonus work’ of carrying that weight during my base and build phases.  That way when I got to my race date and goal weight simultaneously all would be roses and unicorns.

I’m not sure that’s true.  It sounds a bit like a fallacy I invented in my lovely brain to justify going into a training cycle out of shape.

I now am leaning towards nutrition being intricately involved across a training cycle.  I think it support your ability to do the workouts as prescribed and successfully.  I think it impacts your ability to recover and to get better faster.

I think it’s part of a single package that all works together to get the best results.

And that is probably why there is such a close correlation between exercise and weight loss.  Meaning people who begin an exercise program will necessarily be pulled into thinking about their nutrition, diet and weight in a different way to support their exercise.

We see this all the time.

The convers is also true.  People who get into a weight loss or nutrition program to get healthier usually end up going down the exercise rabbit hole.  They go hand in hand.

How many of your runner friends, especially ultra-runners, when you get into a conversation about their backgrounds you discover they have lost a large amount of weight in their journey?

So the answer to the question does losing weight make you faster is ‘yes’.  It makes you faster in the pure physical equation.  You only have so much energy and the more energy you use fighting gravity, the less you can use for propulsion.  Less mass fighting gravity means more propulsion and voila, speed.

I would be remiss to not mention that this can be taken too far.  There is a point where too much weight loss, especially if you are starving the body of what it needs to recover, has a negative impact.

You will see this in competitive runners.  It’s a form of athletic anorexia.  The brain thinks; ‘if losing weight makes me faster, losing more weight will make me even faster’.  But there is a point of diminishing returns.  Eventually the body breaks down.

In these athletes you will see a lot of stress fractures and other serious injuries.  Combined with over-training it is a vicious cycle that ends careers.

In conclusion.  Losing weight makes you faster, but good nutrition makes you faster and healthier.

I’m no nutrition expert, but, one could make the leap that might make you happier as well.

My recommendation would be to buy 3 months of a nutrition coach’s time with the intent to do what they tell you and learn as much as possible.

Then you can judge for yourself.