I do NOT like those mainstay bars. Shit like that is just empty calories. You get no nutrients out of it and you gotta eat so many of the damn sugar cookies to get the calories. You are better off throwing in a few protein bars (350-450 cals per plus vitamins) and some multi vitamins. Check out MAINEPREPPER, he has a video talking about it.
Also as others have said go with dehydrated over canned for the weight/content. Also, an empty bag of mountain house is a lot easier to stow then an empty can of beefaroni. Think E&E, what you pack in you MUST pack out. Even burying stuff could potentially give you away. And think about your worst case scenario. You want stuff lighter/tighter so you can carry more.
If you go the MRE route, consider taking the entree and a couple other small essentials out of the big back. Sure it night be nice to have a couple of those meals with all the shit in them for comfort sake but its just adds up to weight/space.
LIGHTS:
Shit, this is a big one and I am a member of the LWA (Light Whore Anonymous, affiliated with gear whore anonymous lol). As stated weapon lights are powerful, sometimes bulky and usually attached to heavy things lol. Here are my arguments towards getting a headlamp:
1. Allows you to keep your hands free (biggy)
2. is most of the time very compact and lightweight
3. should give you just enough light for your PERSONAL space.
A headlamp is supposed to be used for personal illumination (maybe minor signaling in a pinch). It should just be bright enough to light the ground around your feet and a map in your hands, so you won't be needing an 800 lumen one! You can find ones for only 10-20 bucks that have both red and white LEDs on them. ***SIDE NOTE: something I heard from an eye doctor, a dim white light is better at preserving night vision than a bright red light. Here is a nifty link I found
http://flashlightreviews.com/qa/nightvision.htm***
Now, as we are talking about being as light as possible, why not get a versatile light? I personally use the Streamlight Compact Sidewinder. It is designed for the military, has red, blue, white and IR (the MIL version, commercial I believe has green) lights with multiple intensity modes. The clip allows it to attach to MOLLE, and you can get mounts to place it on helmets and rails as well as a strap to use it like a headlamp!
(OK I'm done with that lol)
I definitely like and agree with a lot of what everyone else has added to the topic as well. Fight light but do it right.