For me it matters a LOT.

I have to watch my sodium and potassium intakes carefully, so I am always thinking "if I take this" or "I really shouldn't eat that". Also, up until this summer I usually carried both my food and my son's. He eats more than I do! So Often I was carrying 4 lbs of food a day! Ahhhhh!

Even with him carrying his own food now I am thinking in advance of what will be the biggest bang for the weight, and that he will like the taste of. I try to stay away from pure sugar for him so that it lasts energy wise (though I do let him indulge a bit!).

I would suspect I think about it more than most people do.