Pack a big bag of healthy foods that can be eaten quickly. I wouldnt suggest shakes if your moving around and doing physical labor, last thing you want when your lifting heavy boxes is the squirts.

Depending on your goals, you should be able to get a lot of cals simply by eating whenever you get a chance. I used to be in and out of court all day long with my old job, so I would keep beef jerky, premade sandwiches, celery, carrots, ect around me and munch when I could. I also always had a big jug of water with BCAA's in it, and some crystal light mixed in for flavor.

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I don't do this for my family, my friends, women, accolades, pride, or ego. I do it for me and no one else, its just part of who I am.