Lack of fitness, fluid or ?

Went on a 13 km walk in Cleland Conv. Park SA with The Fiend of the Heysen Trial on Sunday. Temperature was nice, between 15 to 22oC. Carried about 6.5kg in my pack. Drank about 300ml water, have a small chocolate bar, 2 lollies and a glucose tablet on the way. Found myself pretty stressed towards the last bit of the walk, i.e. I was huffing and puffing and need to stop frequently on the last climb. Lost 350g on the 4 hrs walk.
Was sweating a lot and find it very hot while walking uphill , but no problem when on flat.
Beside carrying less, improving my fittness level, should i have drank more water, eat more, use my ventolin or just walk slower to avoid such situation in future ?
Managed to regain the 350g by eating like a pig in the past 24hrs
Was sweating a lot and find it very hot while walking uphill , but no problem when on flat.
Beside carrying less, improving my fittness level, should i have drank more water, eat more, use my ventolin or just walk slower to avoid such situation in future ?
Managed to regain the 350g by eating like a pig in the past 24hrs
