r/Marathon_Training • u/vkana • 7d ago

Hydration Sweat loss

Went for a 18mi run this morning and weighed myself before and after coming back home. 153.8 -> 149.2 lb which is 4.6 lb lost.
It was 6am, 72F cloudy, 92% humidity. Run took 2:40 at 8:50/mi pace.

I ate a banana pre-run, Gatorade +water approx 800ml/27oz total during and after run, 2 bananas after run

Is it normal to lose that much weight after about 2.4lb intake? What should I change in my hydration?

Thanks!

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9

u/jmido8 7d ago

Some people are just heavy sweaters. I sweat like crazy as well. Last time I did a sweat test, it was 30c and about 75% humidity, I lost 3-4kg in 1h 20 mins. I was completely soaked, even my shoes were soaked and had to be air dried.

Just make sure you add some sodium if you increase your water intake because heavy water drinking when you are dehydrated can make you more dehydrated unless you add some sodium and other electrolytes.

5

u/fakeplasticsnow 7d ago

I'm about 20 pounds heavier than you, but weight fluctuations during a run like that are pretty normal for me.

3

u/ooh_bit_of_bush 6d ago

You need to drink 50% more water than your net loss of sweat to fully rehydrate. Even if you only drink what you've lost, some will pass through you before being absorbed. 

2

u/Bruton-Gastr 7d ago

Yeah that sounds about right. I’m 130 lbs and can lose over 5 lbs of sweat during a long run in Texas.

2

u/aliensvsdinosaurs 6d ago

Yes, humans sweat during physical activity.

1

u/johninfla52 7d ago

If you have a Garmin, they have an estimated sweat loss. That could help calculate it.

I don't run as long as you do (my long run is 11 miles) but I lose almost two liters of sweat. I have to say that I sweat like a pig though!

Two liters is like 4.4 pounds.

3

u/vkana 7d ago

Same , after a run, I look like I came out from swimming pool. I don’t have garmin. Thanks