random question... do you have any mercury fillings in your teeth?
You say your skin gets worse with dehydration. Do you think you're actually hydrated? You drink 4 litres of water a day minimum - do you drink more than 800ml/1litre per hour? How much fruit do you eat? Do you, for example, slam back a litre of water and then 20/30 minutes later start on a smoothie? Do you add additional water to your smoothies? How much sodium do you consume, and in what form? How is your sleep - do you fall asleep easily and not wake during the night?
I'm wondering if you're actually absorbing the fluid you consume, or whether it's simply flushing through you. Any more fluid (which includes that found in fruit) than 800ml/1litre per hour will simply flush through you and not be made use of by the body - disrupting the balance of electrolytes as it goes. A key electrolyte is sodium, so I'm also wondering if you're consuming enough of this, as this is needed in order for the water to actually hydrate you, and also needs to be considered in relation to the amount of potassium you'll be consuming on this diet.
Plus you'll be sweating out sodium during exercise and replenishing with straight water, I suspect, causing further imbalance.
Consuming too much fluid and not enough sodium causes a stress reaction in the body, encouraging the body to store fat (due to the excess cortisol etc produced) and will likely also disturb your sleep. If you are stressing your endocrine system in this way, exercise will exacerbate the situation, encouraging the storage of more fat.
Other than being hydrated on a cellular level, if that's all good, then for the skin issues I'd look at increasing your fat to 10%.
OK so, you are consuming more than 1litre of fluid in an hour? By having a litre of water before breakfast and lunch, followed fairly immediately by fruit? Why do you have an additional litre between dinner and bedtime? Are you thirsty? Your pee should be yellow when you wake up, so that's fine.
If you are consuming more than 1litre of fluid an hour, a three-pronged approach is required - spacing out your fluid consumption (water and fruit) to a level the kidneys can handle, reducing your water intake (as you eat fruit all day), though I say this not knowing if you're exercising in the tropics or something like that which would naturally require higher levels of water, and boosting your sodium intake. It would be good to pimp the water you consume while exercising into a home-made sports drink for now, simply by adding sugar and salt (check out ratios online) to ensure the water gets into your cells. From your first post, you're not consuming enough sodium in relation to your fluid and potassium intake. From you second post..... what do you occasionally eat that has a larger quantity of salt? If you suddenly eat a large amount of salt when dehydrated (or even hydrated), it will worsen the situation, hence the extra thirst, but I say that not knowing just how much salt you ate at those times.
Yes, you do count fruit, you count all fluids, so definitely start spacing this out and reducing your water a bit if you can. Cooked rice is generally around 60% water, so perhaps you wake up dehydrated simply because you are dehydrated, nothing to do with the rice itself.
I'm afraid I can't give you a steer on how much sodium to ingest as I don't know what your current serum levels are. Why don't you begin by making the sports drink? Often dehydrated people find this incredibly satisfying, so see how that goes. And that'll definitely start getting you better hydrated. Aside from that, you need to add loads more greens to your diet. Or the odd sprinkle of salt - whatever works for you, or gives you the quickest results. You don't want to suddenly hit your dehydrated bod with a load of sodium (like with Indian food) but rather have it little and often during the day, ideally with carbs, so that it can get into your cells and work with the water to hydrate you as each day progresses.
Sorry I can't be more precise. I hope I've helped a bit.
Yeah, usually people will crave salt if they're deficient, but equally, this isn't always the case. As you say, perhaps things aren't severe enough at this stage, as you're sleeping OK, so your body doesn't sound like it's going through massive stress.