There doesn't seem to be any penalty if you run away, and fighting only drains your health. Nobody lives forever. Your best bet is to keep searching for food, you're going to find weapons, med kits and bullets; you won't need any of course. If someone offers you food for an item, just give them what they want, food doesn't go bad or get stolen. This game is hard if you focus only on killing and looting, but easy if you enjoy free food and running away. I liked it a lot.