Interesting thread.
There is a fair amount of psycology attached to hot food.I for one would not be happy to go for more than one day without a hot meal of some kind.
This is absolutely true. A hot meal cheers us up (has been proven to), and is more satisfying. In the morning, a hot meal is excellent as it quickly warms you up and gets you ready for the day ahead. The Marines I believe drink Mocha - hot chocolate and coffee mixed - which is perfect as it's a) warming b) sugary, for instant energy and c) stimulating from the caffeine to wake you up.
Imagine struggling all day through heavy rain. You're wet through, you get your tent up or hammock slung, everything is soaked. You're freezing cold, and all you have to eat is cold, and what's more, you have to go out and forage for it. Madness!
I thought the point of dehydrated foods was you only carried that bit with you and picked up the water as you go. That way you're only carrying enough water for your immediate needs. If you carry fruit and vegs you may as well carry all the water anyway as you're not really saving a great deal of weight - are you?
Wouldn't you need to carry or find at least some water, surely you can't live solely on the fluids in apples etc, and if you can, you'd need an awfull lot of them to get the 2 litres per day you 'need'.
A lot more than 2 litres if you're walking. Also, by not carrying water, you can't have any drinks. Carrying fresh food all the time is of course heavier than carrying dehydrated food. If you need to forage every time, you could easily put yourself in the dangerous situation of having no food at all.
Unfortunately for us humans, we just have to drink - we can never hope to get enough water from our diet - even for fruits with a water content of around 80%, to get 2 litres of water from say oranges, if they were 100g each you'd need to eat 25 a day - not something I'd relish doing!
Nutritionally by weight, most higher energy foods naturallyl have less water in them. For example, to make 100g of simple bread/pastry, you only need 1-2 tbsp of water. However, this would give you say 4-500 calories. 100g of orange would only give you around 50 calories.
Thus for a day, (if you only ate oranges or only pastry )
Calories needed - average man: 2500
Water needed - 2 litres
I have to butt in here and say that when I walk, I base my calorie intake on a daily expenditure of 5000kcal. This may be more than other people but it would be a short day indeed that you needed only 2500kcal. Also, if you're walking, you should have at least a litre of water every two hours, or up to one an hour if it's strenuous or warm.
On oranges - 50 oranges = 5.0kg, no water - note you'd be taking too much water by eating these!
On pastry - 5 'portions' = 500g pastry mix + 2 litres water = 2.5kg
I know this is over-simplified, but the fact is that carrying water is almost unavoidable if you want to balance out water intake against energy intake - the nutritional value of most fruit (in basic energy terms at least) is not enough to justify taking them instead of water. 20% by weight of an orange (i.e non-water) is a waste compared to 20% dry mix/80% water of the same weight.
I might also add (no offence intended Keith) that not to carry water is highly irresponsible - you may not know when you'll next find some.
You also can't really sustain a large balanced diet when walking, as a) there isn't a lot of food around that doesn't belong to farmers, or anyone else, and b) you're having to rely on finding food when you get there - even in prehistoric times, when there were very few people and a great deal more food, they couldn't rely on that!
The main advantage is keeping your nutrient intake high - dehydratred food and non-fresh food of most kinds lacks nutrients, so it's a good idea to take vitamin C tablets if you're not going to have access to fresh food in a while. You also save the weight of a stove and fuel.