bitchy I think that the water is always minimum 2 litres but yes you are right you need more the more you have to lose.
I will see if I can find it.
Here it is, copied and pasted for the May BC...
"The more weight you have to lose, the more water you should drink. This is from www.low-carbdiet.co.uk/. Water is essential to weight loss for those who eat low-carb. The minimum consumed in a day should be:
Your Weight----Litres
140lbs-----2.5
160lbs-----3.0
180lbs-----3.0
200lbs-----3.5
220lbs-----3.5
240lbs-----4.0
260lbs-----4.5
280lbs-----4.5
300lbs-----5.0
320lbs-----5.5
340lbs-----5.5
360lbs-----6.0
380lbs-----6.5
400lbs-----6.5
High levels of ketones in the blood stream can lead to a reduction in ketone production, therefore being well hydrated could aid in keeping the levels low and ketone production ongoing. Consuming enough water can have many other positive side effects: aids your kidneys with the processing of protein, reduces the retention of water, helps with preventing constipation, and reduces the levels of ketones released by your breath, which in-turn will reduce breath odour.
However, drinking a lot of water can mean that you also need to keep an eye on your electrolyte balance. You need to make sure that you are consuming sufficient sodium and potassium. On a low carb diet we can eat more salt, so make sure that you are cooking with salt and adding salt to food, if you like it. Good, low carb, sources of potassium are spinach (raw), avocado, mushrooms, courgettes and asparagus, as well as salmon and yoghurt.