Franco, i can and often do eat MUCH less than most people and water is plentiful where i usually hike--springs every 10 miles or so. While i'm not sure, i also think there is a considerable size difference between us. I'm a shade under 5' 7" and weigh around 150lbs (i don't know exactly of late as our big weigh scale is not accurate anymore).
But i will grant you, perhaps i was being a bit wee optimistic on the overall weight. But if it's nice, warmish weather, i can get it down to "around" 4.5 lbs no problemo. The pack i use is less than 3 oz. The full shelter (tarp, bug net, groundsheet, stakes, cord) will total no more than 14 oz, my quilt can without straps is like 15 oz. I could tie some foam to the pack to use instead of the NeoAir M. all season pad, that would be around 6 or so oz.
Here's an idea of what i sometimes eat. Today at work, i helped move a family into a new place (not something i normally do). So, heavy lifting and manual labor essentially for a good 3 hours or so. Previously, for breakfast i ate a very small bowl of brown rice crisp cereal with a little low fat goat milk.
For lunch (during the move), i ate a few celery sticks, a few pieces of baby carrots, and a few cherry tomatoes, and some water. A little while after, i ate a fiber 1 bar.
That held me till around 6 p.m. when i ate some low fat frozen yogurt. Havne't eaten since and not hungry. Most people don't have a conception of how little calories i tend to consume at times, even when my body is fairly active. My weight is normal, healthy, etc. despite that.