Jar of creamy peanut butter. Good source of energy.
In-game description

Peanut butter is a food item in The Long Dark. It has a decent weight-to-calorie ratio, but still loses out to other foods like the Energy bar or MRE.

It is somewhat uncommon and can be found rarely as a random spawn or at locations such as houses.

Food and drink
Canned Condensed milkDog foodPinnacle peachesPork and beansTomato soup
Animal meat Black bearMooseRabbitVenisonWolf
Fish Coho salmonLake whitefishRainbow troutSmallmouth bass
Plant Cat tail stalk
Miscellaneous Beef jerkyCandy barEnergy barGranola barMilitary-Grade MREPeanut butterSalty crackersTin of sardines
Water UnsafePotable
Soda OrangeGrapeSummit
Miscellaneous Herbal teaCoffeeEnergy drink