Fat Adaptation and Water Requirements

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  • #20158

    I was struck by an interesting thought and was wondering if anyone knew of any research or other evidence to back it up:

    Fat-adapted athletes may require less water intake during activity because water is a by-product of fatty acid metabolism. So not only do they have to carry less food, but also less water.

    This was spurred by observing that recently, endurance-trained mountain athletes seem to carry very little water. Steve House himself recently put out a video saying people tend to carry too much water, and how you’d be surprised by how little water you can get away with. Or Jornet’s everest summit where he carried 1L of water for 8 hours of activity. And so forth.

    Anyway, I am not a biologist. Just an idea and wondering if this has been studied.

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    Anonymous on #20228

    This is certainly a possibility. Water is a byproduct of lipolysis. Personally I have noticed that I seem to need less water when out for long days in the mountains. Since I’ve been coaching more and more mountain athletes I frequently hear that they also record much less water consumption that would be expected for their activity. Elite alpinists like David Goettler routinely does multi-hour, strenuous workouts on alpine terrain in Chamonix drinking 1/2 liter of water and one gel.

    Another benefit for the highly fat adapted mountain athlete.


    smarshall54 on #20233

    How would you go about even studying this?

    Alpine environments are dry, but usually pretty cool so not a lot of sweat. Maybe one experiment comparing ultra-runners water intake at high/dry/cool location vs. a desert race vs. a hot/humid race to see how climate affects water intake. Maybe there is already research on this part?

    Then you’d need two groups of athletes that were gas-exchange tested, split into fat-adapted and non-fat-adapted groups, and do some sort of treadmill test measuring power output during a long-duration activity with amount of water and calorie intake held constant for both groups.

    To separate the effects of calorie intake and water intake on power output, you’d have to give the amount of calories needed for the non-adapted group to both groups, and the amount of water given should be the amount required by the fat-adapted group. So everybody has enough calories to support their metabolism, but not enough water for the non-adapted group.

    Then if the hypothesis is correct, you’d expect to see the non-adapted athletes power drop off first since their water intake is limited.

    weird confounding factor is that over-feeding the fat-adapted athletes might actually make their power drop off since the digestion of the excess carbohydrate itself requires extra water. I’m not sure how one might tease this one out.

    Anonymous on #20257

    I think we might just want to rely on anecdotal evidence here:-). You can do an experiment on yourself and see if you notice a reduction in water consumption when fat adapted. My guess is that you will.


    Steve House on #20302

    Personally I think that carrying less water is simply an adaptation brought on by…yup, drinking less water. BUT that is not to say that my overall water consumption is less because I drink more before exercise and more after. I start hydrated and end thirsty.

    At high altitudes or really dry air (Alberta Canada on a cold day) a hard candy to suck on helps keep your throat from becoming so raw.

    Anonymous on #20305

    I’ve read that it isn’t mild dehydration that slows athletes down, but thirst. So to a point, is it psychosomatic?

    Interesting read: https://www.plewsandprof.com/single-post/2015/11/10/Summer-breeze-skateboards-the-perfect-combination (No idea why “skateboards” is in the URL…)

    I rarely take water because I hate carrying it. As Steve said, that has probably reduced my need for it because I’m used to going without.

    This year, I did some experimenting to find just how much water I lose at different intensities and temperatures. That led to doing some ~2h skimo races without a water bottle because dehydration at race pace for two hours would be less than 3%. There was no performance decrement. In fact, it saved me over a pound of equipment because I could leave the bottle at home.

    For me, two hours seems to be the magic mark for food and water. At two hours or less, neither are necessary. In fact, I suspect they may be counter to performance. In races, they’re excess weight to carry. In training, the calories are excess weight to store and run counter to glycogen depletion.

    Over two hours, both are necessary, and I need to start consuming both within the first hour of activity. Watch alarms are key to keep me on a feeding schedule.

    An exception to my two-hour rule is multi-day races. In that context, even if one day’s event is less than two hours, I would still feed and hydrate. It’s irrelevant to that day’s performance but speeds recovery for the following days.

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