Shooting 1 deer will give 8-9 kilo of meat, that alone will get you through 10 days, however it will void some of the other achievments. If you are not going for the other achievements then you can eat any food you find/kill.

Listen out for the crows, the area I mentioned are also deer locations. This gives ample time to stumble upon carcasses. Following this route should give you about 60 Cat Tail plants each providing 150 calories and this quantity alone should easily get you through 4 -5 days. Then head up from the Lake following the frozen water towards Alan's cave. My tactic was to head from Jeremiahs Cabin straight to Unnamed Pond, harvest the Cat-Tail plants around the perimeter of the pond, then follow the Frozen creek which will lead you across to Mystery lake, harvest the plants these all grow on the riverbanks so follow the rivers edge around in a lap. You' ll rely on finding carcasses and looting/surveying areas killing anything will void pacifisct achievement and firing a gun will void silent hunter. If you are working towards the other achievements then this will limit your options. If you played the story you should also be very familiar with the area.

I recommend starting in Mystery Lake, the area is much smaller and main locations far easier to reach and travel between. The Pacifist achievement in The Long Dark worth 269 points Survive the first 25 days without killing anything (single game).

The long dark difficulties