How much weight do people lose during marathons?

In the one marathon in which I weighed before and after, I lost 7 lbs. That might be a tad high but not too far off the norm I think.

Virtually all of it is water. At the most you will burn enough calories to lose 1 lb of fat.

8 lbs sounds right. But I agree, almost all water.

Wow, that's almost 7% of his body weight.

that's why it sounded so ridiculous to me!

dks wrote:

Wow, that's almost 7% of his body weight.

if you weigh yourself before and after a long run (12+ miles) on a hot day in the summer it's not uncommon to lose 3 or 4 lbs. It's all water and it is easily gained back just from drinking liquids. Hardly any of it is fat.

I've lost 7 pounds on a 12 mile run before, and it was only about 70 degrees outside. I wouldn't be at all suprised if they lost more than 8.

Yeah. If you actually keep track, you'll be surprised how much you lose. When I played high school football, we had to weigh ourselves at the beginning and end of summer two-a-day practices so that the trainers could make sure that no one was at risk for dehydration related health problems (if you lost more than 15 lbs in a day and hadn't gained it back the next morning, they would hold you out of practice). It was not unusual at all for guys to sweat out 10 pounds over the course of the practice. Running a marathon is certainly more grueling than a football practice.

POW: I've lost 7 pounds on a 12 mile run before, and it was only about 70 degrees outside. I wouldn't be at all suprised if they lost more than 8.

Beyond a certain dehydration %, performance falls off a cliff. I don't have those numbers at hand but methinks if someone were gonna lose much more than those 8 lb or so, it'd strongly behoove him to drink more during the race instead.

Here is a thread that I started when I lost 7 lbs. after a mararthon. Jack Daniels replied with some good info from research he had one on the subject.

http://www.letsrun.com/forum/flat_read.php?board=1&id=1893603&thread=1893603

I lost 9 pounds and didn't feel dehydrated or even particularly thirsty after.

elites are crazy wrote:

"By the time I start the Dubai Marathon I will weigh 58kg. By the time I finish, I will weigh 54kg."

8 lbs?? that can't be right can it?

8 x 2.2 = 8.8 pounds.

I usually lost 3 pounds for 10 miles and 7 pounds for 20 miles when I was training for marathons, and maybe 9 or 10 pounds for the races. It was usually very hot at the time. I always drank 1/2 gallon of water before starting, which accounted for almost 1/2 of that weight.

Do you mean 4 x 2.2 (lb/kg) = 8.8 lb?

J.R. wrote:

elites are crazy wrote:

"By the time I start the Dubai Marathon I will weigh 58kg. By the time I finish, I will weigh 54kg."

8 lbs?? that can't be right can it?

8 x 2.2 = 8.8 pounds.

I usually lost 3 pounds for 10 miles and 7 pounds for 20 miles when I was training for marathons, and maybe 9 or 10 pounds for the races. It was usually very hot at the time. I always drank 1/2 gallon of water before starting, which accounted for almost 1/2 of that weight.

SMJO wrote:

I lost 9 pounds and didn't feel dehydrated or even particularly thirsty after.

if you lost that much weight and weren't at all thirsty means you were most definitely dehydrated. thirst is NOT a good indicator of hydration status.

Drinking a lot of water won't help much, in fact it can be dangerous if it dilutes cells too much causing low sodium/potassium levels, hyponatremia, which can and does kill people in extreme circumstances.

Sipping water is what you should do. Even then a marathon runner is going to lose 6-10 pounds on average.

hmmmmm wrote:

SMJO wrote:

I lost 9 pounds and didn't feel dehydrated or even particularly thirsty after.

if you lost that much weight and weren't at all thirsty means you were most definitely dehydrated. thirst is NOT a good indicator of hydration status.

I didn't say I wasn't thirsty but the fact that I lost 9 pounds had little impact on my performance.

I think people forget that Glycogen loading involves combining carbs and water at something like a 3:1 ratio so much of the loss isn't real weight.

weIInow wrote:

Drinking a lot of water won't help much, in fact it can be dangerous if it dilutes cells too much causing low sodium/potassium levels, hyponatremia, which can and does kill people in extreme circumstances.

Anyone who runs 100 miles a week does need to drink plenty of water. In the form of fresh veggie juices is the best, which is full of minerals. Even straight water is not going to deplete your body of minerals, but you could die from not drinking enough water. You don't get any minerals from WATER anyway. Minerals come from food, not water.

Sipping water is what you should do. Even then a marathon runner is going to lose 6-10 pounds on average.

Sip a little water, then lose 6-10 pounds? Given I was 137 pounds prior to drinking 1/2 gallon of water, and 133 after running 20 miles, your sipping a little water and then losing 10 pounds would have put me at 127. Would you then sip water after that too instead of replenishing? How many marathons have you run?

Anyone running many miles in training, and racing marathons, does need to drink water.

I happened upon the following last night, p65 from Buddy Edelen's "A Cold Clear Day" biography by Frank Murphy.

"I lost 8.8 pounds (4kg) during the race. I was 148.5 when I started and slightly less than 140 when I finished."

Buddy ran 2:28 in this marathon, October 7, 1962; than ran a world's fastest marathon of 2:14:28 on June 15, 1963.

SMJO wrote:

I didn't say I wasn't thirsty but the fact that I lost 9 pounds had little impact on my performance.

I think people forget that Glycogen loading involves combining carbs and water at something like a 3:1 ratio so much of the loss isn't real weight.

I agree. However I wonder if we might benefit from taking on sodium and potassium in significant amounts at about mile 17?

I once tried a new drink 15 miles into a hard 18 miler and was surprised by how salty it tasted, but it worked really well. When I got home I checked the sodium content and it was extremely high.