So you weren't eating on the trail? When you stop eating carbs, body uses carbs, carbs contain water, body removes water (think 4kg of water), the water remove

So you weren't eating on the trail? When you stop eating carbs, body uses carbs, carbs contain water, body removes water (think 4kg of water), the water removes electrolytes, you get "sick". A spoon of table salt in water fixed it once for me.