Weight Gain and Hyponatremia: Thoughts By Dr. Lisa Bliss

2007 Badwater Finish Line Photo from Lisa's Blog Entry: "Goodwater"

Keeping your electolytes and fluids balanced is one of the trickiest and most important parts of ultra-running. This week on the Ultra-List, Dr. Lisa Bliss discussed the causes of weight gain, hyponatremia and how to keep our bodies in balance during ultramarathons. Dr. Bliss was the 2007 Badwater Female Winner and is the medical director for some of the world's toughest ultras. The following is taken directly from her Ultra-List response; it's a bit long but has tons of great information, especially with rising temperatures just around the corner:

Consuming a very large amount of salt is one (dangerous) way of maintaining a normal sodium level despite weight gain, but it is not a necessary condition. Here are a couple common scenarios seen at ultras:

1) Runner has a daily diet normally low in sodium but takes extra salt - in whatever form - during an ultra. She gains weight, like Ray K says, because salt causes the body to retain water. Sometimes, it doesn't take much. Many can testify that sometimes there is noticeable fluid retention, say in the ankles, just from eating a bowl of popcorn in front of the TV or, in my case, a slice of this fine Lou Malnati's deep dish spinach Chicago style pizza I just received on dry ice from a friend... but I digress....

Salt helps the body retain water. That's why we give 0.9 normal saline IV's to runners who are dehydrated. Salt and water hydrate better than water alone.

No matter what the normal daily dietary intake of salt, if a runner takes "too much" salt, water will be retained in the tissues as the body attempts to maintain a normal amount in the blood vessels, which is ultimately what matters most (the sodium in the blood vessels) because that is the sodium electrolyte that the brain "sees" and reacts to as it passes through the body.

There have been runners who have taken too much water AND too much salt (wrongly thinking this is a good way to avoid hyponatremia) and they are overweight and bloated and have swollen legs and/or hands, and their sodium levels in the blood are normal or even HIGH. Now, THAT'S a lot of sodium! Too much. Guaranteed, these runners are not feeling well and, at the very least, are not going to be running their best race in that condition.

Interestingly, the article that Karl referenced mentioned Noakes' article, which notes that there were endurance athletes in the study who gained weight but were not hyponatremic. Hmm.... He then theorized that they must have sodium stores and that sodium was somehow mobilized from these stores into the bloodstream. What he didn't do was account for sodium intake during the run. It is a glaringly obvious omission in my opinion. You can absolutely gain weight (fluid) and have a normal sodium level if you take in sodium. And you can be fine without any problems. But it's a slippery slope. You may also get yourself into lots of trouble. Adding salt to "offset" weight gain is NOT a good thing to do.

So, yes, too much salt can cause fluid retention and weight gain without hyponatremia. Thing is, though, a runner in this situation now has TWO problems to deal with: too much of two things - water and sodium. Adding more salt to an already fluid overloaded body is not the solution for preventing hyponatremia. A fluid overloaded body requires.... less fluid! Don't try to solve a problem by creating another.

2) BUT... there is another scenario where there may be weight gain even without taking in too much salt or too much fluid. We see it in the longer ultras, the 100-mile and 100+ mile races, especially the hotter races and multiday races. It's the problem of edema. Most of us have encountered it at some point with longer ultras. That's why we sometimes bring a larger shoe size in case our feet swell up. Feet can swell from too much fluid, too much salt and fluid, or they can swell despite optimal fluid and electrolyte balance. It's a consequence of the "pounding" of the muscles and the "pooling" of fluid in the feet from us forcing them to carry us for100+ miles down the roads or trails.

For an example, look at the legs of the runners in a multiday event or an event like Badwater. There can be significant pooled fluid in the legs. If the fluid is in the legs and there are indentations on the skin from your socks or your shoes are tight, etc., then the fluid is in the tissues, NOT in the blood vessels. So, now you can have an increase in weight on the scale but not necessarily an increase in fluid in the blood vessels, which is where the sodium is. So, an electrolyte test can be perfectly normal in this situation despite the increased or level weight, and I would argue that you could even be somewhat *dehydrated* intravascularly (where it matters!) if you are carrying extra fluid body's tissues but do NOT have optimal fluid and electrolyte replacement.

So, here's a question for Lulu. If a runner on day 3 of a multiday run is up 2 pounds and is not feeling well, should we assume he is hyponatremic? Well, we should consider it for sure, but is it necessarily the case? Do you tell him to stop drinking because he's up 2 pounds? Do you hold him at the aid station until his weight comes down? Should we refuse him fluids if he says he is thirsty? Well, if the fluid is in the tissues, it does not dilute the sodium in the blood. Weight gain and leg swelling does not preclude the possibility of hyponatremia, but the weight gain should be evaluated in context, and contexts can become quite complex at some of these ultras.

Fluid from significant swelling (and even fluid hanging out in the gut) are more a concern AFTER the race when those fluids gets mobilized back into the blood stream and finally to the kidney where they can be eliminated from the body. It's when the fluids go back into the blood stream that we have to be careful, especially if we are also rehydrating post-race. That's the most common time for hyponatremia to happen and that's why.

I bring up these scenarios to show that it's not always so black and white, that weight gain, while a red flag for sure, does not *always* mean imminent danger, nor does it mean that someone should necessarily stop drinking. Hyponatremia must remain in the differential; it has very real possible consequences, but it's not quite the science some of us think it is or wish it were, at least in ultrarunning.

In the end, there is NO advice on this topic that can replace personal experience and training. Training and more training. That is the ultimate answer to all the questions. Learn, read, listen, but above all, pay attention to your body and find out what works for you and make adjustments. My experience comes from reading, listening, watching, treating, and above all, making mistakes and learning from them. In the past, I've gained up to 10% of my weight and lost up to 8%.

Scales are excellent to train with and, in my opinion, essential (and easy) at races like Badwater. It was fun for me to make a game of trying to guess my weight when I trained in Death Valley before the race last year. Ask Nancy Shura, who believes in the scale too. I ran about 20 miles to Stovepipe Wells and wanted to catch up with Danny W who was making his way up to Townes Pass. But I was feeling "dry" and fatigued, not so uncommon feelings in the desert. I wasn't peeing. I got on Nancy's scale and was 6 pounds down. Instead of trying to chase down Danny (which I never would have been able to do anyway), I sat at the pool, ate a hoagie from the store, a big bag of chips and drank over 2 liters of fluid. I was still down a couple pounds but I peed. But I felt better and Nancy drove me to meet up with Danny who was RUNNING up to the pass! I was fine then only because I stopped and took care of the problem before it got too bad.

On the flip side, during the race itself, I strolled into Stovepipe Wells with a slight headache and light-headedness, and I was peeing freely and clear, enough that I suspected I might be hyponatremic. I got on the scale and was down 3% of my weight. I was in clothes that were drenched in water, so I was likely down another 1-2% of my true weight. My tested sodium was mildly low by 1-2 mEq/L. I was surprised at both the scale and my sodium level. I was only mildly hyponatremic (and that occurred over many hours asopposed to very quickly) so the sodium level was NOT the likely cause of my symptoms. My body was, however, getting rid of excess fluid, i.e. peeing, so it was attempting to bring the sodium concentration back up. BUT I was underweight! So, what do you do in this situation? First, dissect the problems out. I was mildly hyponatremic, so that needed to be fixed, and I was moderately dehydrated, and that needed to be fixed too. So, I went back out on the road and increased my fluids AND my Succeed! tabs, and the problems got resolved. I adjusted my intake of both and continued to monitor my weight on the scale because, as we know, conditions (effort, appetite, thirst, temperature) are always changing and we need to roll with whatever's in front of us.

Guidelines and information can be helpful, sure, but they also can hurt you if you are not flexible. We just need to learn, try, adjust, and train.

Lisa Bliss
Spokane, WA